Effects of T cell growth factor/interleukin II on prothymocytes.

The present report describes evidence to show that interleukin 2 (IL-2), in addition to its well known action as a second signal in mitogenic action on mature T cells, functions as a regulator of both proliferation and maturation of immature T lymphocytes. The present experiments extend previous observations indicating that immature thymocytes (Thy1+, L3T4-, Ly2-) are a target of IL-2 action. IL-2 and thymosin fraction V but not interleukin 1 (IL-1) induce differentiation of prothymocytes (Thy1-, L3T4-, Ly2-) obtained from spleens of nude mice as measured by the acquisition of the Thy 1 marker. IL-2, but not thymosin fraction V and IL-1, modulates the proliferation of this cell population. The data indicate that IL-2 may exert a significant regulatory function in T cell ontogeny.