Selective Deletion of CD8⁺ Cells Upregulated by Caspases-1 via IL-18 in Mice Immunized with Major Outer Membrane Protein of Shigella dysenteriae 1 Following Infection

Our data suggested that caspase-3 is downregulated in CD4⁺ cells of immunized BALB/c mice following infection with substantial increased expression of interleukin (IL)-2 and interferon (IFN)-γ, while caspase-1 is upregulated in CD8⁺ cells with decreased expression of IL-4 and IL-10. This indicated an involvement of Fas-mediated lytic pathway for selective deletion of CD8⁺ cells out of CD3⁺ T cells. IL-18 promotes inflammation and induces IFN-γ and tumor necrosis factor (TNF)-α as the expression of IFN-γ and TNF-α cytokines was evident in this study. It is assumed that the role of caspase-1 in inducing the CD4+ T cell activity increased with IL-18 rather than CD8+ suppressor cell activity. Bcl-2 is capable of inhibiting the Fas/Fas-L-mediated cell death for helper cells. Overall, the findings indicate that majority of the apoptotic cells were CD8⁺ T cells in the groups of infection following immunization, and there might be a selective deletion of T lymphocytes mediated by caspase-1 via IL-18.