Androgen-induced expression of the peripheral blood gamma delta T cell population in the chicken.

Unlike alpha beta T cells, the physiologic significance of gamma delta T cells has remained elusive. In avian species they comprise a large circulating T cell subset. Here we report that in chicken around the time of sexual maturation (4 to 6 mo of age) a significant increase of the gamma delta T cells takes place in male but not in female chickens. The frequency of gamma delta T cells increases both in peripheral blood and spleen, but not in intestinal epithelium. This expansion is independent of MHC haplotype, being observed in various inbred and MHC-recombinant strains. Furthermore, administration of testosterone to young female chickens induces an equivalent increase in the frequency of gamma delta T cells in peripheral blood. These results indicate that sex, through androgens, has an effect on the gamma delta T cell numbers in a species, in which these cells form a major subset of peripheral lymphocytes.