title: The contribution of CD4+ CD25+ T-regulatory-cells to immune suppression in sepsis.
abstract: Studies have indicated that there is a development of generalized immune dysfunction after septic insult. However, the mechanisms responsible for these changes remain unclear. Recently, accumulating evidence shows that several lymphocyte subpopulations such as NKT-, CD4(+)-Th2-T-, CD8(+)-T-, gammadelta-T-, and CD4+ CD25+ T regulatory cells are capable of actively contributing to the induction of septic immune suppression. Thus, our aim was to investigate the contribution of CD4+ CD25+ cells to the immune dysfunction seen in sepsis. To study this, C57BL/6J, C57BL/6-Il6(tm1Kopf) (interleukin [IL] 6 -/-), and C57BL/6-Il10(tm1Cgn) (IL-10 -/-) mice were subjected to cecal ligation and puncture (CLP) or sham operations. Twenty-four hours later, blood was collected, and splenocytes were isolated. Phenotypic expression of CD4/CD25 (by fluorescence-activated cell sorter), cell proliferation (presented as proliferation index = [with anti-CD3]/[without anti-CD3]), and immune suppressive capacity (by in vitro add-back experiments) were assessed. The results indicate a marked elevation in CD4+ CD25+ cell levels and their proliferation index after sepsis in background mice. CD4+ CD25- cells from sham and CLP mice proliferated equally. However, coculture of CD4+ CD25- with CD4+ CD25+ cells suppressed their proliferation in both sham and CLP mice. Depletion of CD25+ cells in vivo before CLP markedly restored CD4+ CD25- proliferative capacity and Th1 cytokine release while not altering plasma proinflammatory cytokine levels. Subsequently, IL-6 -/- and IL-10 -/- mice were used to elucidate the possible mediator(s) regulating the changes seen after sepsis. Although CD4+ CD25+ cells increased after septic insult in both C57BL/6J and IL-6 -/- mice, this was not observed in IL-10 -/- mice. Similarly, in vitro proliferation studies showed that proliferation index increased in CD4+ CD25+ cells from septic C57BL/6J and IL6 -/- mice, but it remained the same in IL-10 -/- mice. Surprisingly, depletion of CD25+ cells before inducing sepsis did not alter septic mortality. Together, these findings suggest that although CD4+ CD25+ T regulatory cells induced by IL-10 seem to contribute to aspects of sepsis-induced lymphoid immune suppression, the oblation of CD25+ cells does not provide a survival advantage or disadvantage.
authors.affiliation: Shock-Trauma Research Laboratories in the Division of Surgical Research, Department of Surgery, Rhode Island Hospital and Brown University School of Medicine, Providence, Rhode Island 02903, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wisnoski
authors.forename: Chun-Shiang
authors.initials: CS
authors.lastname: Chung
authors.forename: Yaping
authors.initials: Y
authors.lastname: Chen
authors.forename: Xin
authors.initials: X
authors.lastname: Huang
authors.forename: Alfred
authors.initials: A
authors.lastname: Ayala
mesh_terms: D000818:Animals; D017252:CD3 Complex / Q000378:metabolism; D015704:CD4 Antigens / Q000096:biosynthesis*; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D002469:Cell Separation; D016753:Interleukin-10 / Q000378:metabolism*; D053645:Interleukin-2 Receptor alpha Subunit / Q000096:biosynthesis*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018805:Sepsis / Q000097:blood / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D018417:Th1 Cells / Q000166:cytology; D018418:Th2 Cells / Q000166:cytology; D014018:Tissue Distribution
chemical_list: D017252:CD3 Complex; D015704:CD4 Antigens; D053645:Interleukin-2 Receptor alpha Subunit; D016753:Interleukin-10