title: CD4+ T cells mediate abscess formation in intra-abdominal sepsis by an IL-17-dependent mechanism.
abstract: Abscess formation associated with intra-abdominal sepsis causes severe morbidity and can be fatal. Previous studies have implicated T cells in the pathogenesis of abscess formation, and we have recently shown that CD4(+) T cells activated in vitro by zwitterionic capsular polysaccharides from abscess-inducing bacteria such as Staphylococcus aureus and Bacteroides fragilis initiate this host response when transferred to naive rats. In this study, we show that mice deficient in alphabetaTCR-bearing T cells or CD4(+) T cells fail to develop abscesses following challenge with B. fragilis or abscess-inducing zwitterionic polysaccharides, compared with CD8(-/-) or wild-type animals. Transfer of CD4(+) T cells from wild-type mice to alphabetaTCR(-/-) animals reconstituted this ability. The induction of abscesses required T cell costimulation via the CD28-B7 pathway, and T cell transfer experiments with STAT4(-/-) and STAT6(-/-) mice demonstrated that this host response is dependent on STAT4 signaling. Significantly higher levels of IL-17, a proinflammatory cytokine produced almost exclusively by activated CD4(+) T cells, were associated with abscess formation in Th2-impaired (STAT6(-/-)) mice, while STAT4(-/-) mice had significantly lower levels of this cytokine than control animals. The formation of abscesses was preceded by an increase in the number of activated CD4(+) T cells in the peritoneal cavity 24 h following bacterial challenge. Confocal laser-scanning microscopy analysis revealed that CD4(+) T cells comprise the abscess wall in these animals and produce IL-17 at this site. Administration of a neutralizing Ab specific for IL-17 prevented abscess formation following bacterial challenge in mice. These data delineate the specific T cell response necessary for the development of intra-abdominal abscesses and underscore the role of IL-17 in this disease process.
authors.affiliation: Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Doo Ryeon
authors.initials: DR
authors.lastname: Chung
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Kasper
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Panzo
authors.forename: Tanuja
authors.initials: T
authors.lastname: Chitnis
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Grusby
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Sayegh
authors.forename: Arthur O
authors.initials: AO
authors.lastname: Tzianabos
authors.forename: Tanuja
authors.initials: T
authors.lastname: Chtinis
mesh_terms: D018784:Abdominal Abscess / Q000235:genetics / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control; D000818:Animals; D015703:Antigens, CD / Q000502:physiology; D018122:B7-1 Antigen / Q000502:physiology; D051940:B7-2 Antigen; D001442:Bacteroides Infections / Q000235:genetics / Q000276:immunology / Q000473:pathology / Q000517:prevention & control; D001441:Bacteroides fragilis / Q000276:immunology; D018106:CD28 Antigens / Q000235:genetics / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002465:Cell Movement / Q000235:genetics / Q000276:immunology; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D007106:Immune Sera / Q000008:administration & dosage; D007111:Immunity, Cellular / Q000235:genetics; D016130:Immunophenotyping; D020381:Interleukin-17 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000276:immunology / Q000502:physiology*; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010529:Peritoneal Cavity / Q000382:microbiology / Q000473:pathology; D050797:STAT4 Transcription Factor; D050800:STAT6 Transcription Factor; D018805:Sepsis / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics / Q000502:physiology
chemical_list: D015703:Antigens, CD; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D018106:CD28 Antigens; C497965:Cd86 protein, mouse; D004268:DNA-Binding Proteins; D007106:Immune Sera; D020381:Interleukin-17; D008562:Membrane Glycoproteins; D050797:STAT4 Transcription Factor; D050800:STAT6 Transcription Factor; C494091:Stat4 protein, mouse; C494100:Stat6 protein, mouse; D015534:Trans-Activators