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Interleukin (IL)-10 is an anti-inflammatory cytokine that modulates sepsis by decreasing pro-inflammatory cytokine production and chemokine expression. In this study, IL-10-deficient and wild-type (WT) mice were infected with Corynebacterium kutscheri to determine if the absence of IL-10 altered the protective immunity and pathogenesis. After infection, IL-10 knockout (KO) mice had a higher survival rate than WT mice. The decrease of body weight and the increased weight of organs such as liver and spleen were greater in WT mice. Bacterial counts were significantly increased after inoculation in WT mice over those in IL-10 KO mice. WT mice had more granulomatous inflammation and coagulative necrosis in the liver and spleen, lymphocyte depletion in lymphoid follicles, and apoptosis of immune cells in the spleen. WT mice had significantly higher plasma concentrations of aspartate aminotransferase and alanine aminotransferase. Furthermore, more upregulation of tumor necrosis factor-α and IL-4 in the plasma, macrophage inflammatory protein-2, keratinocyte-derived chemokine, inducible nitric oxide synthase, and interferon-inducible protein 10 mRNA in the spleen were observed in WT mice after inoculation. These results suggest that the lack of IL-10 contributes to an increase in the systemic clearance of C. kutscheri, and that IL-10 plays a detrimental role in controlling systemic C. kutscheri infection.

We report, herein, an attempt to determine whether an IL-10-induced immunological state affects the response of macrophages against Salmonella Typhimurium (ST). Pretreatment with mrIL-10 induced the intracellular invasion of ST into macrophages in a dose-dependent manner. It also activated AKT phosphorylation, cyclin D1, Bcl-X(L), and COX-2 upon ST infection, which may correlate with Salmonella's survival within the macrophages. However, I-κB phosphorylation was shown to be inhibited, along with the expression of TNF-α and MIP-2α mRNA. Therefore, IL-10 not only suppresses the bactericidal response of macrophages against ST, but also ultimately causes infected macrophages to function as hosts for ST replication.

IL-10 is an important anti-inflammatory cytokine that can inhibit the production of many pro-inflammatory cytokines. Both human and animal studies have shown that pro-inflammatory cytokines play an important role in pneumonia and other inflammatory lung diseases. In the present study, IL-10 knockout (KO) and wild-type mice were infected with Corynebacterium kutscheri to determine whether the severity of pathogenesis and whether protective immunity could be altered in the absence of IL- 10. The survival rate was significantly lower in IL-10 KO mice than wild-type mice. The number of neutrophils in bronchoalveolar lavage fluid and blood were found to be higher in IL-10 KO mice than wild-type mice. IL-10 KO mice showed greater neutrophil infiltration, excessive inflammation, and weight-loss compared with wild-type mice. Furthermore, upregulation of IFN-gamma in bronchoalveolar lavage fluid, and upregulation of MIP-1alpha and IP-10 mRNA in the lungs of IL-10 KO mice compared with wild-type mice after C. kutscheri infection were observed. These results suggest that IL-10 plays an important role in the anti-inflammatory properties against C. kutscheri infection, and that lack of IL-10 leads to a more severe pulmonary inflammatory response. This increased susceptibility to C. kutscheri pneumonia is at least in part caused by IL-10 deficiency and severe recruitment of neutrophils.