gamma/delta T cell-deficient mice have impaired mucosal immunoglobulin A responses

Mucosal tissues of mice are enriched in T cells that express the gamma/delta T cell receptor. Since the function of these cells remains unclear, we have compared mucosal immune responses in gamma/delta T cell receptor-deficient (TCR delta(-/-)) mice versus control mice of the same genetic background. The frequency of intestinal immunoglobulin (Ig) A plasma cells as well as IgA levels in serum, bile, saliva, and fecal samples were markedly reduced in TCR delta(-/-) mice. The TCR delta(-/-) mice produced much lower levels of IgA antibodies when immunized orally with a vaccine of tetanus toroid plus cholera toxin as adjuvant. Conversely, the antigen-specific IgM and IgG antibody responses were comparable to orally immunized control mice. Direct assessment of the cells forming antibodies against the tetanus toroid and cholera toxin antigens indicated that significantly lower numbers of IgA antibody-producing cells were present in the intestinal lamina propria and Peyer's patches of TCR delta(-/-) mice compared with dir orally immunized control mice. The selective reduction of IgA responses to ingested antigens in the absence of gamma/delta T cells suggests a specialized role for gamma/delta T cells in mucosal immunity.