Abstract
Our previous studies have shown that antigen-specific mucosal immune responses are induced in CD4 gene disrupted (CD4-/-) mice after oral immunization with tetanus toxoid (TT) plus cholera toxin (CT) as mucosal adjuvant. Furthermore, CD4-CD8- T cells showed significant levels of antigen-specific proliferative responses in both mucosal and systemic lymphoid tissues. In this study, we further elucidated nature of antigen-specific CD4-CD8- T cells in those immunized mice. Analysis of TT-specific T cell responses showed that CD4-CD8-, but not CD8+, T cells in Peyer's patches (PP) produced Th2-type (IL-4 and IL-5) cytokines after oral immunization with TT plus CT. Furthermore, CD4-CD8- T cells isolated from PP of immunized CD4-/- mice when added to B cell cultures induced increased number of TT-specific IgG and IgA producing cells. These results suggest that CD4-CD8- T cells in PP of CD4-/- mice are capable of inducing antigen-specific T helper cytokines and provide help for mucosal IgA antibody responses in the absence of CD4+ T cells.
