Adult murine T cells activated in vitro by alpha-fetoprotein and naturally occurring T cells in newborn mice: identity in function and cell surface differentiation antigens.

Murine alpha-fetoprotein (alphaFP) has been shown to suppress T cell-dependent antibody responses in vitro but not T cell-independent responses. Our earlier preliminary findings indicated that such inhibitory effects are mediated via activated T cells. In this study, using alphaFP as the inducing agent, we have analyzed cells generated in vitro from adult spleen cells with regard to function and surface markers and compared the cells to the naturally occurring splenic T cells of newborn mice, in which there are high intrinsic concentrations of alphaFP. Both types of T lymphocytes were found to effectively inhibit T cell-dependent antibody responses in vitro but not T cell-independent responses. Moreover, both groups of T cells were found to express the identical differentiation antigen phenotype,Ly 1 + 2-. Thus alphaFP-induced inhibitory T cells from adults could be shown to have the same functional properties and Ly phenotype as splenic T lymphocytes from newborn mice. These findings support the concept that alphaFP might function as an important immunoregulatory agent in vivo during ontogenetic development.