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.

INTRODUCTION: Mucosal lymphoid changes were observed in cryopreserved rectal tissues obtained from BALB/c mice infected with Shigella dysenteriae 1, immunized with 57-kDa major antigenic outer membrane protein, and infection after immunization. DISCUSSION: 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)-gamma, 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-gamma and tumor necrosis factor (TNF)-alpha as the expression of IFN-gamma and TNF-alpha 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.