Salmonella enterica serotype Typhimurium causes an acute inflammatory reaction in the ceca of streptomycin-pretreated mice that involves T-cell-dependent induction of gamma interferon (IFN-γ), interleukin-22 (IL-22), and IL-17 expression (genes Ifn-γ , Il-22 , and Il-17 , respectively). We investigated here the role of IL-23 in initiating these inflammatory responses using the streptomycin-pretreated mouse model. Compared to wild-type mice, the expression of IL-17 was abrogated, IL-22 expression was markedly reduced, but IFN-γ expression was normal in the ceca of IL-23p19-deficient mice during serotype Typhimurium infection. IL-23p19-deficient mice also exhibited a markedly reduced expression of regenerating islet-derived 3 gamma, keratinocyte-derived cytokine, and reduced neutrophil recruitment into the cecal mucosa during infection. Analysis of CD3 ⁺ lymphocytes in the intestinal mucosa by flow cytometry revealed that αβ T cells were the predominant cell type expressing the IL-23 receptor in naive mice. However, a marked increase in the number of IL-23 receptor-expressing γδ T cells was observed in the lamina propria during serotype Typhimurium infection. Compared to wild-type mice, γδ T-cell-receptor-deficient mice exhibited blunted expression of IL-17 during serotype Typhimurium infection, while IFN-γ expression was normal. These data suggested that γδ T cells are a significant source, but not the sole source, of IL-17 in the acutely inflamed cecal mucosa of mice. Collectively, our results point to IL-23 as an important player in initiating a T-cell-dependent amplification of inflammatory responses in the intestinal mucosa during serotype Typhimurium infection.

Salmonella entericaserotype Typhimurium causes an acute inflammatory reaction in the ceca of streptomycin-pretreated mice. We determined global changes in gene expression elicited by serotype Typhimurium in the cecal mucosa. The gene expression profile was dominated by T-cell-derived cytokines and genes whose expression is known to be induced by these cytokines. Markedly increased mRNA levels of genes encoding gamma interferon (IFN-γ), interleukin-22 (IL-22), and IL-17 were detected by quantitative real-time PCR. Furthermore, the mRNA levels of genes whose expression is induced by IFN-γ, IL-22, or IL-17, including genes encoding macrophage inflammatory protein 2 (MIP-2), inducible nitric oxide synthase (Nos2), lipocalin-2 (Lcn2), MIP-1α, MIP-1β, and keratinocyte-derived cytokine (KC), were also markedly increased. To assess the importance of T cells in orchestrating this proinflammatory gene expression profile, we depleted T cells by using a monoclonal antibody prior to investigating cecal inflammation caused by serotype Typhimurium in streptomycin-pretreated mice. Depletion of CD3⁺T cells resulted in a dramatic reduction in gross pathology, a significantly reduced recruitment of neutrophils, and a marked reduction in mRNA levels ofIfn-γ,Il-22, Il-17, Nos2, Lcn2, andKc. Our results suggest that T cells play an important role in amplifying inflammatory responses induced by serotype Typhimurium in the cecal mucosa.