Previous studies in vivo have shown that IL-10 infusion can prevent lethal endotoxic shock. Mice deficient in the production of IL-10 (IL1OT) were used to investigate the regulatory role of IL-10 in the responses to LPS in three experimental systems. In a model of acute endotoxic shock, it was found that the lethal dose of LPS for IL1OT mice was 20-fold lower than that for wild type (wt) mice suggesting that endogenous IL-10 determines the amount of LPS which can be tolerated without death. The high mortality rate of IL1OT mice challenged with modest doses of LPS was correlated to the uncontrolled production of TNF as treatment with anti-TNF antibody (Ab) resulted in 70% survival. Additional studies suggested that IL-10 mediates protection by controlling the early effectors of endotoxic shock (e.g., TNFa) and that it is incapable of directly antagonizing the production and/or actions of late appearing effector molecules (e.g., nitric oxide). We also found that ILAOT mice were extremely vulnerable to a generalized Shwartzman reaction where prior exposure to a small amount of LPS primes the host for a lethal response to a subsequent sublethal dose. The priming LPS dose for IL1OT mice was 100-fold lower than that required to prime wt mice implying that IL-10 is important for suppressing sensitization. In agreement with this assumption, IL-10 infusion was found to block the sensitization step. Interestingly, IL-10 was not the main effector of endotoxin tolerance as ILAOT mice could be tolerized to LPS. Furthermore, IL-10 infusion could not substitute for the desensitizing dose of LPS. These results show that IL-10 is a critical component of the host's natural defense against the development of pathologic responses to LPS although it is not responsible for LPS-induced tolerance. (J. Clin. Invest. 1995Invest. . 96:2339Invest. -2347

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SummaryMice rendered deficient in the production of interleukin 10 (IL-10 -/-) develop a chronic inflammatory bowel disease (IBD) that predominates in the colon and shares histopathological features with human IBD. Our aim was to identify which cell type(s) can mediate colitis in IL-10 -/-mice. We detected an influx ofimmunoglobulin-positive cells into the colon and the presence of colon-reactive antibodies in the serum of IL-10 -/-mice. To assess a pathogenic role for B cells, we generated a B cell-deficient (B -/-) strain oflL-10 -/-mice. B-/-IL-10 -/-mice acquired a severe colitis analogous to that oflL-10 -/-mice, implying that B cells were not the primary mediator of IBD in this model. A series of cell transfer experiments was performed to assess a pathogenic role for T cells. When IL-10 -/-T cell-enriched lamina propria lymphocytes (LPL) or intraepithelial lymphocytes (IEL) were transferred into immunodeficient recombinase-activating gene (RAG)-2 -/-recipients, a mild to severe colitis developed, depending on the cell number transferred. Lymphocytes recovered from the colon of transplanted R.AG-2 -/-mice with colitis were predominantly otI~TCR+CD4 +, including a large proportion of CD4 § + cells. These cells were also CD45RB -/l~ and CD44 +, indicative of an activated/memory population. Individual populations of CD4+CD80~ -, CD4+CD8oe + and CD4-CD8ot + T cells were then isolated from the lamina propria compartment of IL-10 -/-mice and transferred into RAG-2 -/-recipients. Only IL-10 -/-CD4-expressing LPL, including both the CD4+CD8ot -and CD4+CD8r + populations, induced colitis in recipient mice. Interferon-',/, but little to no IL-4, was produced by CD4+CD8o~ -and CD4+CD8ot § LPL recovered from the inflamed colons of RAG-2 -/-recipients implicating a T helper cell 1 (TH1)-mediated response. We thus conclude that colitis in IL-10 -/-mice is predominantly mediated by THl-type cll3TCtk + T cells expressing CD4 alone, or in combination with the CD8ct molecule.

Abstract:Our studies have elucidated, in part,

SummaryWe have examined the role of endogenously produced interleukin (IL) 4 and IL-10 in the regulation of inflammatory and immune reactions in the skin. In these experiments, irritant and contact hypersensitivity (CH) responses were elicited in mice with targeted disruptions of the IL-4 (IL-4T) or IL-10 (IL-10T) gene. Our study showed that IL-4T and wild-type (wt) mice exhibited equivalent responses to the irritant croton oil. In contrast, the response of IL-10T mice challenged with croton oil was abnormally increased. When IL-10T mice were exposed to a higher dose of irritant, irreversible tissue damage occurred. By comparison, any treatment of wt mice with croton oil resulted in far less tissue damage and resolution of inflammation. Neutralizing antibody studies demonstrated that the necrosis ,hat occurred in Ibl0T mice was due to the overproduction of tumor necrosis factor. The anti-tumor necrosis factor antibody treatment of IL-10T mice did not significantly reduce the edema or the influx of inflammatory cells, suggesting that these changes were due to the uncontrolled production of other proinflammatory cytokines. T cell-dependent immune responses were also evaluated using the contact sensitizer oxazolone. The response of IL-4T mice did not differ from wt mice. In contrast, ILol0T mice mounted an exaggerated CH response, increased in both magnitude and duration as compared with wt mice. Based on these studies, we have concluded that II,-10, but not IL-4, is a natural suppressant of irritant responses and of CH, and it limits immunopathologic damage in the skin.

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IL-10-deficient (IL-10-/-) mice, generated by a gene-targeted mutation, develop abnormal immune responses as a result of uncontrolled interactions between antigen presenting cells and lymphocytes. The studies reviewed herein have focused on the enterocolitis that spontaneously develops in IL-10-/- mice. Not unexpectedly, heightened production of proinflammatory mediators accompanied pathologic changes in the gastrointestinal tract of young mutants. In a series of studies, the proinflammatory mediators responsible for initiating the pathogenic response were distinguished from those that were elicited as a consequence of persistent inflammation. We have also investigated the possibility that different mediators are involved in the inductive versus the maintenance phase of disease. The findings of these mechanistic studies as they relate to our understanding of progressive inflammatory disease and the role of IL-10 in controlling the acute and chronic stages are discussed.

IL-4 is associated with Th2-type immune responses and can either inhibit or, in some cases, promote Th1-type responses. We tested the effect of IL-4 treatment on the development of inflammation in the CD4+CD45RBhigh T cell transfer model of colitis, which has been characterized as a Th1-dependent disease. IL-4 treatment significantly accelerated the development of colitis in immunodeficient recipients (recombinase-activating gene-2 (Rag2)−/−) of CD4+CD45RBhigh T cells. Quantitative analysis of mRNA expression in the colons of IL-4-treated mice showed an up-regulation of both Th1- and Th2-associated molecules, including IFN-γ, IP-10, MIG, CXCR3, chemokine receptor-8, and IL-4. However, cotreatment with either IL-10 or anti-IL-12 mAb effectively blocked the development of colitis in the presence of exogenous IL-4. These data indicate that IL-4 treatment exacerbates a Th1-mediated disease rather than induces Th2-mediated inflammation. As other cell types besides T cells express the receptor for IL-4, the proinflammatory effects of IL-4 on host cells in Rag2−/− recipients were assessed. IL-4 treatment was able to moderately exacerbate colitis in Rag2−/− mice that were reconstituted with IL-4Rα-deficient (IL-4Rα−/−) CD4+CD45RBhigh T cells, suggesting that the IL-4 has proinflammatory effects on both non-T and T cells in this model. IL-4 did not cause colitis in Rag2−/− mice in the absence of T cells, but did induce an increase in MHC class II expression in the lamina propria of the colon, which was blocked by cotreatment with IL-10. Together these results indicate that IL-4 can indirectly promote Th1-type inflammation in the CD4+CD45RBhigh T cell transfer model of colitis.