Reduction of Helicobacter Infection in IL-10−/– Mice is Dependent On CD4+ T Cells but not on Mast Cells

Background: In contrast to wild type, interleukin‐10‐deficient (IL‐10^?/–) mice are able to clear Helicobacter infection. In this study, we investigated the immune response of IL‐10^?/– mice leading to the reduction of Helicobacter infection. Materials and Methods: We characterized the immune responses of Helicobacter felis‐infected IL‐10^?/– mice by studying the systemic antibody and cellular responses toward Helicobacter. We investigated the role of CD4⁺ T cells in the Helicobacter clearance by injecting H. felis‐infected IL‐10^?/– mice with anti‐CD4 depleting antibodies. To examine the role of mast cells in Helicobacter clearance, we constructed and infected mast cells and IL‐10 double‐deficient mice. Results: Reduction of Helicobacter infection in IL‐10^?/– mice is associated with strong humoral (fivefold higher serum antiurease antibody titers were measured in IL‐10^?/– in comparison to wild‐type mice, p < .008) and cellular (urease‐stimulated splenic CD4⁺ T cells isolated from infected IL‐10^?/– mice produce 150‐fold more interferon‐γ in comparison to wild‐type counterparts, p < .008) immune responses directed toward Helicobacter. Depletion of CD4⁺ cells from Helicobacter‐infected IL‐10^?/– mice lead to the loss of bacterial clearance (rapid urease tests are threefold higher in CD4⁺ depleted IL‐10^?/– in comparison to nondepleted IL‐10^?/– mice, p < .02). Mast cell IL‐10^?/– double‐deficient mice clear H. felis infection, indicating that mast cells are unnecessary for the bacterial eradication in IL‐10^?/– mice. Conclusion: Taken together, these results suggest that CD4⁺ cells are required for Helicobacter clearance in IL‐10^?/– mice. This reduction of Helicobacter infection is, however, not dependent on the mast cell population.