help button home button
AJRCCM
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Published ahead of print on August 16, 2007, doi:10.1164/rccm.200606-763OC
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
200606-763OCv1
176/9/921    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Olszewski, M. A.
Right arrow Articles by Toews, G. B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Olszewski, M. A.
Right arrow Articles by Toews, G. B.
American Journal of Respiratory and Critical Care Medicine Vol 176. pp. 921-929, (2007)
© 2007 American Thoracic Society
doi: 10.1164/rccm.200606-763OC

Original Article

Effect of Laparotomy on Clearance and Cytokine Induction in Staphylococcus aureus–infected Lungs

Michal A. Olszewski1,2, Nicole R. Falkowski2, Rishi Surana1,2, Joanne Sonstein1,2, Anne Hartman2, Bethany B. Moore2, Gary B. Huffnagle2,3 and Galen B. Toews1,2

1 The Veterans Administration Ann Arbor Healthcare System, Ann Arbor, Michigan; and 2 Division of Pulmonary and Critical Care, Department of Internal Medicine, and 3 Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan

Correspondence and requests for reprints should be addressed to Michal Olszewski, D.V.M., Ph.D., Research Service (506/11R), VA Ann Arbor Healthcare System, 2215 Fuller Road, Ann Arbor, MI 48105-2303. E-mail: olszewsm{at}umich.edu


   ABSTRACT
TOP
 ABSTRACT
AT A GLANCE COMMENTARY
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Rationale: Staphylococcus aureus is a major pathogen complicating postsurgical care.

Objectives: To test the effect of sterile laparotomy (LAP) on pulmonary clearance of S. aureus in a murine model.

Methods: Control and LAP mice were infected intranasally with 108 cfu of S. aureus. Microbial clearance, pulmonary leukocyte recruitment, and cytokine profiles were compared between the groups. Antibody neutralization or cytokine gene knockout mice were used to evaluate the role of cytokines.

Measurements and Main Results: Laparotomy resulted in a 10-fold increase in S. aureus lung colony-forming units on Days 2 and 3 postinfection. Both groups cleared the infection by Day 4. No defect in leukocyte recruitment into the lungs was observed in infected LAP animals; however, an increase in the number of Mac-3–positive cells and a significant decrease of cells with high surface expression of Fc-{gamma}R suggest suboptimal activation of leukocytes in the lungs of infected LAP animals. Infected LAP mice had decreased expression of interferon (IFN)-{gamma} and increased expression of mRNA for IL-13 in the lungs on Day 1 postinfection and decreased levels of IL-6, keratinocyte-derived chemokine (KC), and macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage at Day 2 postinfection. Neutralization of IFN-{gamma} mimicked the effect of LAP with impaired clearance on Day 2.

Conclusions: Sterile LAP induced temporary deactivation of innate immune responses to pulmonary S. aureus challenge. Impaired microbial clearance was accompanied by altered cytokine expression and suboptimal activation of pulmonary leukocytes. Lack of early IFN-{gamma} induction in the infected lungs of LAP animals is a likely mechanism contributing to the observed phenotype.

Key Words: Staphylococcus aureus • lung • cytokines • innate immunity • macrophages



   AT A GLANCE COMMENTARY
TOP
 ABSTRACT
 AT A GLANCE COMMENTARY
METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Scientific Knowledge on the Subject
Little is known about the natural mechanism of host defenses against the major opportunistic pathogen Staphylococcus aureus.

What This Study Adds to the Field
Sterile laparotomy produces temporary deactivation of innate immune responses to pulmonary S. aureus infection. Lack of early IFN-{alpha} induction is a likely mechanism for these findings.

 
Staphylococcus aureus is a common cause of both hospital- and community-acquired pneumonia (1, 2). The predominance of antibiotic-resistant strains in hospital-acquired S. aureus infections and the emergence of multidrug-resistant community-acquired infections result in high mortality and growing medical costs (3–5). About 25% of hospital-acquired infections (i.e., 500,000) are caused by staphylococci, resulting in an annual death rate of approximately 90,000 patients (6–8).

On the other hand, nasal carriage of S. aureus is common (9–11), and a majority of individuals become S. aureus carriers for a period of time, with only a small fraction ever developing clinical symptoms. This indicates that an intact immune system can effectively recognize and control S. aureus; progressive S. aureus infection arises when these protective mechanisms become either temporarily or permanently impaired. It is likely that expanding our knowledge about endogenous mechanisms responsible for control/clearance of S. aureus will aid the development of novel therapeutic strategies for this pathogen. Pulmonary clearance of S. aureus depends, in part, on phagocytic cells, including resident alveolar macrophages (12), recruited neutrophils (13, 14), and mononuclear phagocytes (15); these cells are capable of ingestion and intracellular killing of S. aureus (12–16).

The impaired pulmonary host response and subsequent clinical infections with S. aureus may be associated with many factors, including underlying diseases such as influenza (17, 18), cystic fibrosis (19, 20), HIV infection (21), chemotherapy (22), diabetes (6), mechanical ventilation (23), and old age. Surgical procedures significantly increase the risk of S. aureus infection (24, 25), and S. aureus is a major pathogen complicating postsurgical care (26, 27). One of the major causes of postsurgical S. aureus infection is a direct contamination of a surgical wound and/or implantation of S. aureus with medical devices on which S. aureus can form biofilms. In addition to these risk factors, we consider the possibility that surgical intervention may impair host defenses, which could result in an increased susceptibility to S. aureus infection. Surgical intervention is reported to produce numerous changes in the immune system, including changes in trafficking and function of leukocytes (28–30). In experimental models, laparotomy (LAP) was shown to cause a decrease in ex vivo phagocytosis of Candida albicans and decreased respiratory burst in peritoneal macrophages (31). Furthermore, LAP was shown to decrease ex vivo proliferative capacity and release of IL-2 and IL-3 by splenocytes isolated at 2 and 24 hours postsurgery (32). It has been also demonstrated that LAP can increase mortalities from bacterial infections and promote pulmonary fibrosarcoma metastases in mice (33). We tested the hypothesis that surgical intervention impairs host resistance to pulmonary S. aureus infection. In this article, we report that sterile LAP alters the innate immune responses during subsequent S. aureus pulmonary challenge, which results in impaired clearance of S. aureus. This impairment is not associated with a deficiency in overall recruitment of leukocytes into the lungs but is associated with an altered cytokine profile in the lungs and altered activation status of pulmonary phagocytes. Some of the preliminary results that were part of these studies have been previously reported in the form of an abstract (34).


   METHODS
TOP
 ABSTRACT
 AT A GLANCE COMMENTARY
 METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Cultures of S. aureus
The S. aureus strain (NCTC 8325) S. aureus subsp. aureus Rosenbach was a gift from Dr. J. Iandolo (University of Oklahoma Health Sciences Center). This strain is characterized by expression of cell wall bound protein A (SPA+), fibronectin binding proteins A and B, and hemolysins a, b, g, d. It is novobiocin, fluoroquinolone, quinolone, rifampin, and tetracycline resistant but sensitive to methicillin. S. aureus cultures were grown from frozen stocks to late logarithmic phase (10 h) in tryptic soy broth (Difco, Detroit, MI) at 37°C on a shaker. The growth of cultures was confirmed by turbidity measurement at {lambda} = 600 nm. Bacteria were purified by centrifugation at 2,000 rpm at 4°C and washed with chilled nonpyrogenic saline (Travenol, Deerfield, IL). Cultures were adjusted to 1010 microbes/ml in sterile nonpyrogenic saline and kept on ice throughout the duration of infection.

Mice
CD-1 outbred mice and IL-13+/+ (BALB/c) mice from Charles River (Wilmington, MA), and IL-13–/– and IL-4/IL-13–/– mice originally obtained from Dr. A. McKenzie (Medical Research Council, London, UK) and bred at the University of Michigan breeding colony were used for these experiments. These mice were housed under specific pathogen–free conditions in enclosed filter top cages at the University of Michigan Unit for Laboratory Animal Medicine. The mice were handled and maintained using microisolator techniques with daily monitoring by veterinary personnel. All the animal procedures and animal protocols were reviewed and approved by the VA Subcommittee for Animal Studies (IACUC) and by the University Committee on the Use and Care of Animals at the University of Michigan.

Sterile LAP and Infection with S. aureus
For surgery and/or the intranasal instillation, mice were anesthetized by intraperitoneal injection of ketamine/xylazine mix (100/6.8 mg/kg body weight). The operation area (lower left abdomen) was clipped and washed with iodine betadine followed by ethanol. A 1-cm incision through the skin and abdominal muscle layers was made, resulting in brief exposure of the peritoneal cavity. The incision was followed by closure with surgical wound staples. For the infection, anesthetized mice received 5-µl of bacterial suspension in the corner of a nostril followed by 10 µl of saline to wash. After inhalation of the inoculum, inoculation of the second nostril occurred in identical fashion. For IL-13 reconstitution studies, mouse recombinant IL-13 (Peprotech, Rocky Hill, NJ) was reconstituted in nonpyrogenic saline and instilled into the nostril in place of regular saline wash, which was given to the control mice.

Assessment of Microbial Load and Leukocyte Populations
To evaluate microbial burden and pulmonary leukocyte numbers, lungs were excised after mice were killed and washed in phosphate-buffered saline, and leukocytes were isolated using an enzymatic dispersion protocol described previously (35, 36). Isolated leukocytes were adjusted in cell culture media, and enumerated in 0.04% trypan blue using a hemocytometer. Differential counts were performed in cytospun slides (Shandon Cytospin, Pittsburgh, PA), fixed/stained by a three-step Diff-Quik whole blood stain (Diff-Quik; VWR Scientific Products, Bridgeport, NJ). A total of 200–400 cells were counted for each sample from randomly chosen, high-power microscopic fields. Colony-forming unit assay of digested lungs was performed as described previously to evaluate microbial load (32).

Collection of Broncheoalveolar Lavage Fluid
After mice were killed, bronchoalveolar lavage (BAL) fluid was obtained as described previously (32). The recovered fluid (1.4–1.8 ml total) was spun at 1,500 rpm. The supernatant was removed and stored at –20°C for further cytokine/chemokine analysis, whereas the cells were used for flow cytometry.

Monoclonal Antibodies
The following monoclonal antibodies (mAbs) from BD Biosciences (San Jose, CA) were used: 30-F11 (anti-murine CD45, rat IgG2b), M1/70 (anti-murine CD11b, rat IgG2b), HL3 (anti-murine CD11c, hamster IgG1), 2.4G2 (anti-murine CD16/CD32 Fc block, rat IgG2b), M3/84 (anti-murine Mac-3, rat IgG1), and RB6-8C5 (anti-murine Ly6G Gr-1, rat IgG2b). mAbs were primarily conjugated with fluorescein isothiocyanate, biotin, or phycoerythrin; biotinylated Abs were visualized using streptavidin–PerCP (BD Pharmingen). Isotype-matched irrelevant control mAbs (BD Pharmingen) were simultaneously tested in all experiments.

Antibody Staining and Flow Cytometric Analysis
Cells from BAL fluid were stained and prepared for flow cytometric analysis. Staining of Fc-{gamma} receptors (Fc-{gamma}R) and analysis by flow cytometry were performed as described previously (35, 36). Fc block was used in all stainings except for stainings involving Fc-{gamma}R. Mac-3 staining was used to define newly recruited macrophages and Gr-1 staining was used to identify neutrophils and activated macrophages. CD11b and CD11c staining was used as an additional identifier of macrophages, and Fc-{gamma}R staining was used as a measure of macrophage activation.

Detection of Cytokine mRNA by Reverse Transcriptase–Polymerase Chain Reaction
Whole lungs were removed and homogenized in TRIzol reagent (Invitrogen, Carlsbad, CA), and RNA was extracted as described previously (32). One step reverse transcriptase–polymerase chain reaction (RT-PCR), oligonucleotide primer sequences for cyclophilin (housekeeping gene), IFN-{gamma} and IL-13, conditions for RT-PCR, and confirmation by Southern blot were performed as described previously (32).

Cytokine Detection in BAL Fluid
IFN-{gamma}, tumor necrosis factor (TNF)-{alpha}, IL-10, keratinocyte-derived chemokine (KC), IL-6, macrophage inflammatory protein-2 (MIP-2), and macrophage inflammatory protein-1{alpha} (MIP-1{alpha}) in BAL fluid were quantified using specific ELISA kits for the respective murine cytokines (BD Biosciences) and analyzed as described previously (32).

Calculations and Statistics
Data (mean ± SE) for each experimental group were derived from at least two independent infections and analyzed via t test or one- or two-way analysis of variance, depending on the number of groups. For individual comparisons of multiple groups, post hoc Tukey's test was used to calculate P values. Survival between the groups was compared using Kaplan-Meier survival analysis coupled with a log rank test. Means with P values less than 0.05 were considered statistically significant.


   RESULTS
TOP
 ABSTRACT
 AT A GLANCE COMMENTARY
 METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Effect of Sterile LAP on Mouse Survival after S. aureus Infection
Our first goal was to evaluate the impact of extrathoracic surgery on mortality associated with pulmonary S. aureus infection. CD-1 mice were subjected to sterile LAP or anesthesia alone (control), and infected 24 hours later with 108 cfu of S. aureus 8325 intranasally. At 24 hours postinfection, no difference in survival was seen between LAP and control mice (Figure 1). However, at 72 hours postinfection, mortality in the LAP group was double that of the control group; 20% mortality was observed in the LAP group at this time point compared with 10% in the infected control group. No mice had died from surgery alone; survival of uninfected LAP animals that received intranasal saline during the time of infection was 100%. Thus, LAP contributed to an increased mortality in mice with pulmonary S. aureus infection.


Figure 1
View larger version (33K):
[in this window]
[in a new window]

  		Figure 1. Effect of sterile laparotomy (LAP) on the survival of Staphylococcus aureus–infected CD-1 mice. Mice underwent sterile LAP or were treated with anesthesia alone (control). Animals from each group were infected with 108 cfu of S. aureus 8325 via intranasal (IN) route or received an equivalent dose of nonpyrogenic saline. Mice were monitored for survival. n = 20 mice/group. Data represent mean of two experiments. *P < 0.05, Kaplan-Meier analysis.

 
Effect of LAP on Pulmonary Clearance of S. aureus
To determine if increased mortality from S. aureus pneumonia in LAP mice was caused by decreased clearance of S. aureus from the lungs, we measured pulmonary S. aureus burden at 24, 48, and 72 hours postinfection. Infected LAP mice demonstrated greater lung burden compared with infected control mice on Days 2 and 3 postinfection (Figure 2). In 81% of infected control mice, S. aureus load in the lungs was below the limit of detection at 72 hours. In contrast, nearly half of infected LAP animals had detectable S. aureus in their lungs. Surviving animals in both groups eventually cleared the infection. To determine if LAP resulted in increased dissemination of S. aureus from the lungs into the blood, homogenized spleens were serially diluted and cultured. Dissemination from lung into the blood (spleen) was minimal. Fewer than 5% of animals had cultures positive for S. aureus, and very few bacteria could be detected during the first 48 hours of infection (data not shown). Severe pulmonary hyperemia and fluid collection in the thoracic cavity were found in the animals that died of the infection. Thoracic fluid was either clear or tinted with blood and was heavily infected with S. aureus. Thus, LAP resulted in a temporarily impaired pulmonary clearance of S. aureus, which resulted in uncontrolled growth of S. aureus in the lungs and the development of pulmonary pathology in the subset of infected animals.


Figure 2
View larger version (8K):
[in this window]
[in a new window]

  		Figure 2. Effect of sterile laparotomy (LAP) on pulmonary clearance of S. aureus. After inoculation, S. aureus load in enzymatically dispersed lungs was analyzed by culturing serially diluted samples on tryptic soy agar. Percentages above the 72-h bars indicate percentage of mice that cleared the infection. Data were calculated and represent cfu/whole lung. Data are pooled from three separate experiments and are expressed as the mean cfu/lung ± SE. *P < 0.05 in comparison with control.

 
Effect of LAP on Leukocyte Recruitment into the S. aureus–infected Lungs
The depletion of neutrophils with anti–Gr-1 antibody resulted in 100% mortality within 48 hours of infection (data not shown). To determine if a defect in pulmonary leukocyte recruitment was responsible for impaired S. aureus clearance post-LAP, we compared the inflammatory cell composition in the lungs of LAP and control animals. Infected and uninfected lungs were dispersed enzymatically and total lung leukocyte and differential cell counts were determined. LAP did not result in deficiency in leukocyte recruitment on Days 1, 2, or 3 postinfection. However, a slight increase in leukocyte recruitment was observed in LAP mice on Day 1 postinfection (data not shown). This increase was no longer present on Days 2 and 3 postinfection. No difference in pulmonary neutrophil (Figure 3A) or mononuclear phagocyte recruitment (Figure 3B) was seen between infected control and LAP mice.


Figure 3
View larger version (10K):
[in this window]
[in a new window]

  		Figure 3. Effect of sterile laparotomy (LAP) on pulmonary recruitment of neutrophils and mononuclear phagocytes in mice infected with S. aureus (Days 1–3). Cells were isolated from infected lungs (n = 11) via enzymatic mince digest (see METHODS). (Recruited leukocytes in infected mouse) = (total number of leukocyte in infected mouse) – (mean number of leukocytes in uninfected mice) (n = 11 uninfected mice).

 
To determine if pulmonary leukocytes were equally present in the alveolar space, leukocytes were analyzed in BAL fluid using flow cytometry. The number of CD45+ cells in the airspace was virtually identical for both control and LAP animals at Day 2 postinfection (control: 1.58 ± 0.34 x 106 cells; LAP: 1.43 ± 0.36 x 106 cells). Differential cell counts also revealed similar numbers of mononuclear phagocytes (control: 8.8 ± 2.3 x 105 cells; LAP: 9.8 ± 2.8 x 105 cells) and neutrophils (control: 19.6 ± 7.9 x 105 cells; LAP: 24.0 ± 4.4 x 105 cells) in the airspace of infected control and LAP mice at Day 2 postinfection. No significant difference was noted in numbers of Gr-1–positive cells in the alveolar space of control and LAP mice at Day 2 postinfection (Figure 4A). Interestingly, an increase in the number of Mac-3–positive cells was observed in the airspace of LAP mice when compared with control mice at Day 2 postinfection (Figure 4A). No difference in the numbers of cells expressing CD11b or CD11c was observed in the BAL fluid of infected mice with or without LAP (Figure 4B). However, LAP did result in a significant decrease of cells with high surface expression of Fc-{gamma}R, suggesting that the phagocytes recruited into the alveolar space of the infected LAP mice were not fully activated (Figure 4A).


Figure 4
View larger version (23K):
[in this window]
[in a new window]

  		Figure 4. Effect of sterile laparotomy (LAP) on the recruitment of neutrophils and mononuclear phagocytes into the airspace of mice infected with S. aureus. (A) Cells from bronchoalveolar lavage fluid were isolated from uninfected control, infected control, and LAP mice and were stained with anti–Gr-1, anti–Mac-3, and anti–Fc-{gamma}R antibodies. (B) Data from cells stained with anti–CD-11b and anti-CD-11c are represented as histograms; isotype controls are shown in red and stained samples are shown in blue. Dashed lines show the number of GR-1, Mac-3, and Fc-{gamma}R positive cells lavaged from uninfected control mice. Bars represent mean ± SE, n = 2–3 per group (control and LAP); *P < 0.05 in comparison with control group. NS = not significant.

 
Thus, impaired pulmonary S. aureus clearance post-LAP was associated with a differential expression of activation markers by pulmonary leukocytes.

Effect of LAP on S. aureus–induced Cytokine Production by Lung Leukocytes
Differential activation of leukocytes in the alveolar compartment could be a result of changes in the cytokine profile that is produced in response to S. aureus infection in the lungs of control and LAP animals. We hypothesized that the rapid clearance in control mice would be associated with robust induction of proinflammatory cytokines (IFN-{gamma} and TNF-{alpha}), whereas delayed clearance in LAP animals would be associated with a decreased expression of these cytokines and/or increased expression of counterregulatory cytokines (IL-10, IL-4, and IL-13). These cytokines were evaluated in the BAL fluid of infected control and LAP animals. Infection with S. aureus resulted in the robust induction of proinflammatory cytokines in the lungs. Both IFN-{gamma} and TNF-{alpha} were significantly elevated in BAL fluid after infection with S. aureus (Figure 5). LAP alone did not result in an induction of these cytokines in the lungs; however, pulmonary induction of IFN-{gamma} was significantly diminished in infected LAP animals at 24 hours postinfection (Figure 5). Interestingly, TNF-{alpha} induction in S. aureus–infected lungs was not affected by LAP, indicating that LAP did not result in an overall defect in proinflammatory cytokine production but specifically affected IFN-{gamma} induction. We evaluated IL-4 and IL-10, cytokines that have regulatory effects to those of IFN-{gamma} and TNF-{alpha}. Both IL-4 and IL-10 were induced in response to S. aureus infection; LAP had no effect on BAL levels of these cytokines in either infected or uninfected lungs. Expression of IL-13 was evaluated by RT-PCR, together with the expression of IFN-{gamma}, at 24 hours postinfection (Figure 6). Consistent with observations at the protein level, mRNA for IFN-{gamma} was strongly induced in the lungs at 24 hours post–S. aureus infection. Furthermore, the expression of IFN-{gamma} mRNA in LAP/S. aureus–infected mice was diminished in comparison with S. aureus–infected control mice (Figure 6). In contrast with robust induction of IFN-{gamma}, IL-13 mRNA expression was only slightly induced in the lungs of S. aureus–infected control mice. RT-PCR analysis showed very modest induction of IL-13 mRNA in infected control mice (Figure 6). A dramatic increase in IL-13 mRNA transcript was found in the lungs of infected LAP mice. Thus, LAP altered the pulmonary cytokine profile observed in S. aureus infection, such that early induction of IFN-{gamma} was decreased and induction of IL-13 was increased.


Figure 5
View larger version (13K):
[in this window]
[in a new window]

  		Figure 5. Effect of sterile laparotomy (LAP) on IFN-{gamma}, tumor necrosis factor (TNF)-{alpha}, IL-4, and IL-10 levels in bronchoalveolar lavage (BAL) fluid. Cytokine levels was measured by ELISA in BAL samples from infected and uninfected control and LAP mice. Bars represent mean ± SE, n = 5–8 per group (control) and 4 per group (LAP); *P < 0.05 in comparison with control group. ND=not detectable.

 

Figure 6
View larger version (28K):
[in this window]
[in a new window]

  		Figure 6. Effect of sterile laparotomy (LAP) on IFN-{gamma} and IL-13 gene expression in S. aureus (SA)–infected lungs (24 h postinfection). Total RNA was extracted from isolated lung leukocytes of uninfected (U) control and LAP mice. Expression of IFN-{gamma} and IL-13 mRNA and the housekeeping gene beta-actin was analyzed via reverse transcriptase–polymerase chain reaction. The polymerase chain reaction products were confirmed by Southern blot with specific DNA probes for each cytokine. Bands shown are representative of three independent experiments, whereas the bar graph shows the relative density ratio of individual IFN-{gamma} and IL-13 bands in comparison to beta-actin intensity from the final experiment (n = 3–4 animal per group).

 
We subsequently analyzed a group of pulmonary cytokines/chemokines that are known to be important in recruitment and activation of leukocytes during the innate host defenses in the lungs. There was an initial increase in innate cytokines/chemokines in both infected control and LAP mice at Day 1 postinfection. Significant differences in pulmonary cytokines between LAP and control groups were not observed until Day 2 postinfection. KC, IL-6, and MIP-2 were all significantly lower in the BAL fluid from infected LAP mice at this time; these differences were no longer significant at Day 3 postinfection (Figure 7). No significant difference was observed in MIP-1{alpha} levels between infected control and LAP mice. Therefore, downstream of impaired IFN-{gamma} and enhanced IL-13 induction, LAP resulted in a decrease of KC, IL-6, and MIP-2 production, which is consistent with the impaired clearance of S. aureus from the lungs of LAP mice.


Figure 7
View larger version (17K):
[in this window]
[in a new window]

  		Figure 7. Effect of sterile laparotomy (LAP) on KC, IL-6, MIP-2, and MIP-1{alpha} levels in bronchoalveolar lavage (BAL) fluid. Cytokine and chemokine levels were measured by ELISA in BAL samples from infected control and LAP mice. Dashed lines represent cytokine/chemokine production by uninfected control mice. Bars represent mean ± SE, n = 7 per group (control) and n = 6 per group (LAP); *P < 0.05 in comparison with control group.

 
Effect of IFN-{gamma} Depletion on S. aureus Clearance from the Infected Lungs
To determine if the altered cytokine response, in particular the absence of an early IFN-{gamma} induction, could explain the delayed clearance of S. aureus from the infected lungs post-LAP, we examined the effect of IFN-{gamma} depletion on pulmonary S. aureus clearance. Similar to LAP animals, there was no difference in pulmonary S. aureus clearance between the control and IFN-{gamma}–depleted mice at 24 hours postinfection, but S. aureus lung burden was greater in IFN-{gamma}–depleted mice at 48 hours postinfection (Figure 8A). Thus, decreased IFN-{gamma} expression could explain transient impairment in pulmonary S. aureus clearance in LAP mice on Day 2 postinfection.


Figure 8
View larger version (25K):
[in this window]
[in a new window]

  		Figure 8. Effect of cytokine depletion on pulmonary clearance of S. aureus. (A) Mice were treated with anti–IFN-{gamma} antibody or control immunoglobulin solution intraperitoneally at 24 hours before and 24 hours after S. aureus infection. Pulmonary S. aureus burden was analyzed in control and IFN-{gamma}–depleted mice. (B) IL-13+/+ and IL-13–/– mice were infected with 108 cfu of S. aureus with or without administration of recombinant mouse IL-13 (rIL-13) (5 µg). Lung colony-forming units were analyzed. Bars represent mean ± SE, n = 5–14 per group. *Significantly different from control; #significantly different from IL-13+/+ with rIL-13; {ddagger}significantly different from IL-13–/– with rIL-13.

 
Effect of IL-13 on S. aureus Clearance from the Infected Lungs
Because LAP was associated with both increased IL-13 induction and delayed clearance of S. aureus from the lungs of LAP mice, we studied the effect of IL-13 gene deletion on pulmonary clearance of S. aureus. We expected that IL-13 gene deletion would enhance pulmonary clearance of S. aureus, particularly in LAP-infected mice. Interestingly, the deletion of IL-13 did not enhance pulmonary clearance. Furthermore, IL-13 gene deletion resulted in delayed clearance of S. aureus, suggesting that IL-13 has a protective role in pulmonary clearance of S. aureus (Figure 8B). The intranasal reconstitution of mouse recombinant IL-13 (5 µg/mouse) resulted in improved clearance (Figure 8B), IL-13–/– mice after IL-13 reconstitution cleared S. aureus with the same rate as the IL-13+/+ mice. Thus, IL-13 contributes to clearance of S. aureus from the infected lungs and therefore increased expression of IL-13 in LAP animals was not responsible for the impaired clearance of S. aureus from the lungs of LAP mice.

Effect of IL-4 and IL-13 Gene Deletion on S. aureus Clearance from the Infected Lungs of Control and LAP Animals
During the pulmonary infection with S. aureus, we observed an induction of IL-4 in both infected control and LAP animals, whereas increased induction of IL-13 was observed only in LAP mice. IL-4 and IL-13 share a common signaling receptor subunit and can thus compensate for each other. To determine if combined signaling of IL-4 and IL-13 was involved in the phenotype of infected LAP mice, we tested the effect of LAP and the effect of combined deletion of IL-4 and IL-13 on pulmonary clearance of S. aureus. The combined deletion of IL-4 and IL-13 resulted in a significantly decreased clearance of S. aureus from the infected lungs. A 100-fold difference in pulmonary colony-forming units between IL-4/IL-13––/–– and IL-4/IL-13++/++ mice was found at 24 hours (of 7.67 ± 0.28 vs. 6.32 ± 0.22 log, n = 4–8, P = 0.03), and at 48 hours (5.81 ± 0.71 vs. 3.62 ± 0.40 log, n = 8, P = 0.005). Reconstitution of IL-13 reversed the defect in clearance at 24 hours (6.05 ± 0.46, n = 6), but this beneficial effect was no longer seen at 48 hours, suggesting that, in the combined absence of IL-4 and IL-13, reconstitution of IL-13 has a partial effect. Our final experiment tested the combined effect of LAP and IL-4/IL-13 deletion. Wild-type and IL-4/IL13––/–– mice were infected with S. aureus. The effect of LAP was additive with the effect of cytokine deletion (Figure 9), indicating that the effect of LAP was not driven by overexpression of these type 2 cytokines.


Figure 9
View larger version (25K):
[in this window]
[in a new window]

  		Figure 9. Effect of IL-4 and IL-13 gene deletion on S. aureus clearance from the infected lungs of control and laparotomy (LAP) animals. IL-4/IL-13 double-knockout mice on BALB/c background (IL-4/IL-13––/––) and their wild-type controls, BALB/c mice, (IL-4/IL-13++/++) were infected intranasally with S. aureus. Pulmonary S. aureus burden was analyzed at 48, 72 and 168 hours postinfection. Appropriate P values are listed above the respective bars.

 

   DISCUSSION
TOP
 ABSTRACT
 AT A GLANCE COMMENTARY
 METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Our studies demonstrate that LAP can interfere with host responses to pulmonary S. aureus infection. Sterile LAP followed by S. aureus pulmonary challenge results in increased mortality and delayed microbial clearance. Delayed pulmonary clearance is not associated with defective leukocyte recruitment, but it is associated with hallmarks of impaired leukocyte activation and an altered pulmonary cytokine profile. LAP results in decreased early induction of IFN-{gamma} and increased expression of IL-13 in response to S. aureus challenge. Subsequently, infected LAP mice demonstrate a premature decline of KC, IL-6, and MIP-2 compared with infected control mice. IFN-{gamma} depletion mimics the effect of LAP in terms of decreased clearance of S. aureus on Day 2 postinfection. In contrast, increased IL-13 expression post-LAP has not proven to be a mechanism of decreased S. aureus clearance after LAP.

Our studies document that abdominal surgery has a deleterious effect on pulmonary innate immune response. This defect is not associated with deficiency or delay in the development of the inflammatory response. Recruitment of neutrophils or monocytes into the lungs is not impeded in infected LAP mice. Adequate leukocyte recruitment in concert with impaired clearance suggests that the effector functions of host defense cells in the lungs are not optimal for clearance of S. aureus. These studies provide a mechanistic explanation for the increased risk of S. aureus infections, including pneumonia, reported in surgery patients (24, 25).

To assess the activation state of recruited cells, we examined the expression of surface receptors in leukocytes obtained by BAL. The analysis was performed on Day 2 postinfection when the first changes in clearance and mortality were observed in infected LAP mice. Expressions of CD11b, CD11c, and Fc-{gamma}R were chosen as surrogates of cell activation, whereas Mac-3 expression was chosen as a surrogate of the resting state of macrophages (37, 38). No difference in expression of CD11b and CD11c was seen when infected LAP and control groups were compared. However, an increase in Mac-3 expression and a decrease in Fc-{gamma}R expression were noted in LAP mice compared with control animals at Day 2 postinfection. These findings are compatible with a lowered state of macrophage activation.

We further demonstrate that the cytokine profile of S. aureus–infected lungs in LAP animals differs from control animals. The early burst of IFN-{gamma} production observed in control infected mice is significantly reduced in infected LAP mice. This is the first report that abdominal surgery adversely affects the induction of IFN-{gamma} in the lungs in response to an infectious agent (39). Our finding is consistent with a recent report of decreased IFN-{gamma} and IL-12 production by peripheral blood leukocytes in cardiac surgery patients (40). Leukocytes isolated from these patients in the perioperative period had significantly decreased potential to elicit these cytokines in response to staphylococcal enterotoxin B in vitro (40). Little is known about the role of IFN-{gamma} in pulmonary clearance of S. aureus. In murine septic arthritis models, IFN-{gamma} supplementation resulted in increased phagocytosis and protection from septicemia (41, 42). IFN-{gamma} also increased killing of S. aureus in the whole blood (43). On the other hand, IFN-{gamma} increased the incidence of septic arthritis (41) and contributed to high mortality in mice that were injected with a lethal dose of S. aureus (44). In our experiments with the pneumonia model, IFN-{gamma} neutralization resulted in transiently decreased pulmonary clearance of S. aureus on Day 2 but not Day 1 postinfection, which mimics the effects of LAP. This suggests that impaired clearance post-LAP is due, in part, to decreased early induction of IFN-{gamma}. IFN-{gamma} induces up-regulation of Fc-{gamma}R, and this is consistent with our finding of decreased surface expression of Fc-{gamma}R in LAP mice, which could be secondary to decreased IFN-{gamma} induction (45). In aggregate, these findings argue for the direct involvement of IFN-{gamma} in leukocyte activation and clearance of S. aureus.

IL-6 is a multifunctional cytokine that is up-regulated downstream of IFN-{gamma} signaling (46). Previous studies have shown that S. aureus infection induces an increase in IL-6 production (47) and that IL-6 induction is associated with protection in bacterial pneumonia models (48, 49). Induction of IL-6 is observed on Day 1 postinfection in both control and LAP mice. However, IL-6 continues to increase in control mice and declines in LAP mice at Day 2 postinfection. Although decreased ex vivo induction of IL-6 from peritoneal macrophages was reported after LAP (33), our studies are the first to report that LAP may affect in vivo production of IL-6 in a pneumonia model. KC and MIP-2 are murine analogs of IL-8, known to be important in host defense against S. aureus infections (50). Although we observed a robust induction of KC and MIP-2 at Day 1 postinfection in infected control and LAP mice, infected LAP mice exhibited a decreased production of these innate cytokines/chemokines at Day 2 postinfection. The early induction of KC, MIP-2, and MIP-1{alpha} was robust in both infected control and LAP mice, which most likely contributed to a similar magnitude of leukocyte recruitment into the alveolar space. In contrast, the premature decline of these chemokines, and in particular the decreased IL-6, could explain delayed microbial clearance and increased mortality of LAP animals at Days 2 and 3 postinfection.

Interestingly, not all of the tested innate cytokines/chemokines are depressed in infected LAP mice; TNF-{alpha}, IL-4, IL-10, and MIP-1{alpha} levels do not differ significantly from controls. This observation suggests that LAP in conjunction with S. aureus challenge results in alteration of specific innate immunity signaling pathways rather than an overall reduction of all inflammatory parameters. Because a decrease in IFN-{gamma} production occurs in infected mice before any other changes in inflammation/clearance parameters, it is likely that early IFN-{gamma} signaling triggers subsequent mediators that are responsible for the sustained activation of leukocytes and the clearance of S. aureus in the lungs.

The reduced early IFN-{gamma} induction in S. aureus–challenged LAP animals was accompanied by a robust induction of IL-13, which was not observed in the lungs of infected control animals. During innate immune responses, IFN-{gamma} plays a role as an important proinflammatory cytokine, whereas IL-13 is a counterregulatory/repair cytokine (51). The robustly expressed IL-13 in LAP animals was expected to diminish S. aureus clearance; however, there are no published studies regarding the role of IL-13 in host responses to S. aureus. IL-4, which shares a common signaling pathway with IL-13, has been reported to promote septic arthritis in the murine model (52). During innate immunity, cytokines associated with the adaptive Th2 responses, (IL-4, IL-10, and IL-13) often play an antiinflammatory role due to their ability to down-regulate proinflammatory cytokine production, including IFN-{gamma}. Surprisingly, IL-13 deletion did not enhance the clearance of S. aureus, and pulmonary S. aureus clearance was delayed in IL-13 knockout mice. IL-13 reconstitution reversed clearance impairment, demonstrating that IL-13 has a protective effect rather than interfering with the pulmonary clearance of S. aureus. Factors other than IL-13 play an important role in the deactivation of innate immune responses post-LAP. Our studies do not directly address the factors responsible for IL-13 induction in infected lungs of LAP mice, but we believe that IL-13 expression is induced in response to the repair processes after abdominal surgery. It is likely that, in the case of pulmonary infection with S. aureus, the immunostimulatory and immunoregulatory effects of IL-13 (51, 53) add up to an overall protective effect that supports clearance of S. aureus in the absence of IFN-{gamma}. Our final experiment analyzed the combined role of IL-4 and IL-13 in S. aureus–infected lungs. In combination, IL-4 and IL-13 are beneficial in the pulmonary clearance process and the presence of these type 2 cytokines lessens the adverse effect of LAP.

In summary, our studies demonstrate that LAP results in increased mortality and delayed pulmonary clearance in a murine model of S. aureus pneumonia. LAP alone does not induce detectable changes in lung cytokine expression; however, after S. aureus infection, induction of pulmonary IFN-{gamma}, IL-13, IL-6, KC, and MIP-2 are altered. In addition, macrophages from LAP mice are suboptimally activated as evidenced by decreased Fc-{gamma}R expression and increased Mac-3 expression. We conclude that LAP followed by infection causes a transient deactivation of innate immune responses resulting in decreased microbial clearance, altered cytokine/chemokine expression pattern, and incomplete activation of macrophages.


   Acknowledgments
 
The authors thank Dr. Jami Milam, Gerald Montano, David McNamara, Mun Choe, Kevin Coughlin, Dr. Peedikayil E. Thomas, and Gari Martinovski for their assistance in different parts of this project, and the Undergraduate Research Opportunity Program at the University of Michigan for its support.


   FOOTNOTES
 
Supported by a VA Merit Grant (G.B.T.), VA MREP (M.A.O.), and VA REAP (M.A.O., J.S.).

Originally Published in Press as DOI: 10.1164/rccm.200606-763OC on August 16, 2007

Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript.

Received in original form June 8, 2006; accepted in final form August 10, 2007


   REFERENCES
TOP
 ABSTRACT
 AT A GLANCE COMMENTARY
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Fridkin SK, Hageman JC, Morrison M, Sanza LT, Como-Sabetti K, Jernigan JA, Harriman K, Harrison LH, Lynfield R, Farley MM. Methicillin-resistant Staphylococcus aureus disease in three communities. N Engl J Med 2005;352:1436–1444.[Abstract/Free Full Text]
  2. Chambers HF. Community-associated MRSA: resistance and virulence converge. N Engl J Med 2005;352:1485–1487.[Free Full Text]
  3. Rubin RJ, Harrington CA, Poon A, Dietrich K, Greene JA, Moiduddin A. The economic impact of Staphylococcus aureus infection in New York City hospitals. Emerg Infect Dis 1999;5:9–17.[Medline]
  4. Lowy FD. Antimicrobial resistance: the example of Staphylococcus aureus. J Clin Invest 2003;111:1265–1273.[CrossRef][Medline]
  5. Furuya EY, Lowy FD. Antimicrobial-resistant bacteria in the community setting. Nat Rev Microbiol 2006;4:36–45.[CrossRef][Medline]
  6. Laupland KB, Gregson DB, Zygun DA, Doig CJ, Mortis G, Church DL. Severe bloodstream infections: a population-based assessment. Crit Care Med 2004;32:992–997.[CrossRef][Medline]
  7. Chambers HF. The changing epidemiology of Staphylococcus aureus? Emerg Infect Dis 2001;7:178–182.[Medline]
  8. National Nosocomial Infections Surveillance (NNIS) system report: data summary from January 1990–May 1999, issued June 1999. Am J Infect Control 1999;27:520–532.[CrossRef][Medline]
  9. Harbarth S, Sax H, Fankhauser-Rodriguez C, Schrenzel J, Agostinho A, Pittet D. Evaluating the probability of previously unknown carriage of MRSA at hospital admission. Am J Med 2006;119:275, e15–e23.
  10. Sax H, Harbarth S, Gavazzi G, Henry N, Schrenzel J, Rohner P, Michel JP, Pittet D. Prevalence and prediction of previously unknown MRSA carriage on admission to a geriatric hospital. Age Ageing 2005;34:456–462.[Abstract/Free Full Text]
  11. Hidron AI, Kourbatova EV, Halvosa JS, Terrell BJ, McDougal LK, Tenover FC, Blumberg HM, King MD. Risk factors for colonization with methicillin-resistant Staphylococcus aureus (MRSA) in patients admitted to an urban hospital: emergence of community-associated MRSA nasal carriage. Clin Infect Dis 2005;41:159–166.[CrossRef][Medline]
  12. Toews GB, Pierce AK. The fifth component of complement is not required for the clearance of Staphylococcus aureus. Am Rev Respir Dis 1984;129:597–601.[Medline]
  13. Lipscomb MF, Onofrio JM, Nash EJ, Pierce AK, Toews GB. A morphological study of the role of phagocytes in the clearance of Staphylococcus aureus from the lung. J Reticuloendothel Soc 1983;33:429–442.[Medline]
  14. Klucinski W, Winnicka A, Olszewski M, Sikora J, Sitarska E, Niemialtowski M, Muzylak M, Bylinka G, Wyszynski M. Phagocytic activity of polymorphonuclear leukocytes lavaged from the lungs of horses with clinically diagnosed chronic pulmonary disease. Zentralbl Veterinarmed A 1994;41:558–567.[Medline]
  15. Hoidal JR, Schmeling D, Peterson PK. Phagocytosis, bacterial killing, and metabolism by purified human lung phagocytes. J Infect Dis 1981;144:61–71.[Medline]
  16. Toews GB, Gross GN, Pierce AK. The relationship of inoculum size to lung bacterial clearance and phagocytic cell response in mice. Am Rev Respir Dis 1979;120:559–566.[Medline]
  17. Oliveira EC, Marik PE, Colice G. Influenza pneumonia: a descriptive study. Chest 2001;119:1717–1723.[CrossRef][Medline]
  18. Cate TR. Impact of influenza and other community-acquired viruses. Semin Respir Infect 1998;13:17–23.[Medline]
  19. Davidson DJ, Dorin JR, McLachlan G, Ranaldi V, Lamb D, Doherty C, Govan J, Porteous DJ. Lung disease in the cystic fibrosis mouse exposed to bacterial pathogens. Nat Genet 1995;9:351–357.[CrossRef][Medline]
  20. Ulrich M, Herbert S, Berger J, Bellon G, Louis D, Munker G, Doring G. Localization of Staphylococcus aureus in infected airways of patients with cystic fibrosis and in a cell culture model of S. aureus adherence. Am J Respir Cell Mol Biol 1998;19:83–91.[Abstract/Free Full Text]
  21. Goetz AM, Squier C, Wagener MM, Muder RR. Nosocomial infections in the human immunodeficiency virus-infected patient: a two-year survey. Am J Infect Control 1994;22:334–339.[CrossRef][Medline]
  22. Advani SH, Kochupillai V, Lalitha N, Shanta V, Maitreyan V, Nair R, Banerjee U, Kelkar R, Mukherjee S. Infections in the immunocompromised host: a prospective multicenter survey in patients receiving chemotherapy for acute leukemia. J Assoc Physicians India 1996;44:769–773.[Medline]
  23. Woske HJ, Roding T, Schulz I, Lode H. Ventilator-associated pneumonia in a surgical intensive care unit: epidemiology, etiology and comparison of three bronchoscopic methods for microbiological specimen sampling. Crit Care 2001;5:167–173.[CrossRef][Medline]
  24. Celis R, Torres A, Gatell JM, Almela M, Rodriguez-Roisin R, Agusti-Vidal A. Nosocomial pneumonia: a multivariate analysis of risk and prognosis. Chest 1988;93:318–324.[CrossRef][Medline]
  25. Astagneau P. Prevalence of nosocomial infections in France: results of the nationwide survey in 1996. The French Prevalence Survey Study Group. J Hosp Infect 2000;46:186–193.[CrossRef][Medline]
  26. Taylor MD, Napolitano LM. Methicillin-resistant Staphylococcus aureus infections in vascular surgery: increasing prevalence. Surg Infect (Larchmt) 2004;5:180–187.[Medline]
  27. Brook I. Intra-abdominal, retroperitoneal, and visceral abscesses in children. Eur J Pediatr Surg 2004;14:265–273.[CrossRef][Medline]
  28. Sylla P, Nihalani A, Whelan RL. Microarray analysis of the differential effects of open and laparoscopic surgery on murine splenic T-cells. Surgery 2006;139:92–103.[CrossRef][Medline]
  29. Angele MK, Chaudry IH. Surgical trauma and immunosuppression: pathophysiology and potential immunomodulatory approaches. Langenbecks Arch Surg 2005;390:333–341.[CrossRef][Medline]
  30. Bocsi J, Richter M, Hambsch J, Barten MJ, Dahnert I, Schneider P, Tarnok A. Transient Th1/Th2 disbalance indicates postoperative effusions and edema after cardiopulmonary bypass in children. Cytometry A 2006;69:165–168.[Medline]
  31. Redmond HP, Hofmann K, Shou J, Leon P, Kelly CJ, Daly JM. Effects of laparotomy on systemic macrophage function. Surgery 1992;111:647–655.[Medline]
  32. Zellweger R, Ayala A, Zhu XL, Morrison MH, Chaudry IH. Effect of surgical trauma on splenocyte and peritoneal macrophage immune function. J Trauma 1995;39:645–650.[Medline]
  33. Nakamoto T, Yoshimura H, Honda T, Nakata K, Taniguchi Y, Yoshida A, Uenobe M, Yoshioka N, Yamaguchi T, Inagawa H, et al. Treatments for the activating macrophages that reduces surgical stress and postoperative mortalities from bacterial infections and tumor metastases. In Vivo 2007;21:357–364.[Medline]
  34. Olszewski MA, Huffnagle GB, Robson N, Hartman A, Toews GB. Deactivation of pulmonary innate immune response to Staphylococcus aureus occurs following sterile laparotomy, role of cytokines and gamma-delta T-cells [abstract from ATS International Conference]. Am J Respir Crit Care Med 2002;165S:B49.
  35. Osterholzer JJ, Ames T, Polak T, Sonstein J, Moore BB, Chensue SW, Toews GB, Curtis JL. CCR2 and CCR6, but not endothelial selectins, mediate the accumulation of immature dendritic cells within the lungs of mice in response to particulate antigen. J Immunol 2005;175:874–883.[Abstract/Free Full Text]
  36. Olszewski MA, Huffnagle GB, McDonald RA, Lindell DM, Moore BB, Cook DN, Toews GB. The role of macrophage inflammatory protein-1 alpha/CCL3 in regulation of T cell-mediated immunity to Cryptococcus neoformans infection. J Immunol 2000;165:6429–6436.[Abstract/Free Full Text]
  37. Hepburn AL, Mason JC, Davies KA. Expression of Fc-gamma and complement receptors on peripheral blood monocytes in systemic lupus erythematosus and rheumatoid arthritis. Rheumatology (Oxford) 2004;43:547–554.[CrossRef][Medline]
  38. Nibbering PH, Leijh PC, van Furth R. Quantitative immunocytochemical characterization of mononuclear phagocytes. II. Monocytes and tissue macrophages. Immunology 1987;62:171–176.[Medline]
  39. Ooshiro M, Sugishita YI, Tanaka H, Koide K, Nagashima M, Katoh R. Regulation of perioperative immunological changes following laparotomy: effects of biological response modifier (BRM) on surgical stress. Immunol Lett 2004;93:33–38.[CrossRef][Medline]
  40. Franke A, Lante W, Kurig E, Zoller LG, Weinhold C, Markewitz A. Is interferon gamma suppression after cardiac surgery caused by a decreased interleukin-12 synthesis? Ann Thorac Surg 2006;82:103–109.[Abstract/Free Full Text]
  41. Zhao YX, Nilsson IM, Tarkowski A. The dual role of interferon-gamma in experimental Staphylococcus aureus septicaemia versus arthritis. Immunology 1998;93:80–85.[CrossRef][Medline]
  42. Zhao YX, Tarkowski A. Impact of interferon-gamma receptor deficiency on experimental Staphylococcus aureus septicemia and arthritis. J Immunol 1995;155:5736–5742.[Abstract]
  43. DeForge LE, Billeci KL, Kramer SM. Effect of IFN-gamma on the killing of S. aureus in human whole blood: assessment of bacterial viability by CFU determination and by a new method using alamarBlue. J Immunol Methods 2000;245:79–89.[CrossRef][Medline]
  44. Sasaki S, Nishikawa S, Miura T, Mizuki M, Yamada K, Madarame H, Tagawa YI, Iwakura Y, Nakane A. Interleukin-4 and interleukin-10 are involved in host resistance to Staphylococcus aureus infection through regulation of gamma interferon. Infect Immun 2000;68:2424–2430.[Abstract/Free Full Text]
  45. Boruchov AM, Heller G, Veri MC, Bonvini E, Ravetch JV, Young JW. Activating and inhibitory IgG Fc receptors on human DCs mediate opposing functions. J Clin Invest 2005;115:2914–2923.[CrossRef][Medline]
  46. Smith JW, Gamelli RL, Jones SB, Shankar R. Immunologic responses to critical injury and sepsis. J Intensive Care Med 2006;21:160–172.[Abstract/Free Full Text]
  47. Ahn JY, Choi IS, Shim JY, Yun EK, Yun YS, Jeong G, Song JY. The immunomodulator ginsan induces resistance to experimental sepsis by inhibiting Toll-like receptor-mediated inflammatory signals. Eur J Immunol 2006;36:37–45.[CrossRef][Medline]
  48. Mancuso P, Huffnagle GB, Olszewski MA, Phipps J, Peters-Golden M. Leptin corrects host defense defects after acute starvation in murine pneumococcal pneumonia. Am J Respir Crit Care Med 2006;173:212–218.[Abstract/Free Full Text]
  49. Malik M, Bakshi CS, Sahay B, Shah A, Lotz SA, Sellati TJ. Toll-like receptor 2 is required for control of pulmonary infection with Francisella tularensis. Infect Immun 2006;74:3657–3662.[Abstract/Free Full Text]
  50. Rich J, Lee JC. The pathogenesis of Staphylococcus aureus infection in the diabetic NOD mouse. Diabetes 2005;54:2904–2910.[Abstract/Free Full Text]
  51. Minty A, Ferrara P, Caput D. Interleukin-13 effects on activated monocytes lead to novel cytokine secretion profiles intermediate between those induced by interleukin-10 and by interferon-gamma. Eur Cytokine Netw 1997;8:189–201.[Medline]
  52. Hultgren O, Kopf M, Tarkowski A. Staphylococcus aureus-induced septic arthritis and septic death is decreased in IL-4-deficient mice: role of IL-4 as promoter for bacterial growth. J Immunol 1998;160:5082–5087.[Abstract/Free Full Text]
  53. Marshall JD, Robertson SE, Trinchieri G, Chehimi J. Priming with IL-4 and IL-13 during HIV-1 infection restores in vitro IL-12 production by mononuclear cells of HIV-infected patients. J Immunol 1997;159:5705–5714.[Abstract]




This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
200606-763OCv1
176/9/921    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Olszewski, M. A.
Right arrow Articles by Toews, G. B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Olszewski, M. A.
Right arrow Articles by Toews, G. B.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Proc. Am. Thorac. Soc. Am. J. Respir. Cell Mol. Biol.
Copyright © 2007 American Thoracic Society