Studies on T lymphocyte activation I. Requirements for the mitogen‐dependent production of T cell growth factors

Publisher Website
Google Scholar
Abstract
Conditioned media (CM) obtained from concanavalin A (Con A)‐stimulated spleen cell cultures maintain mitogen‐derived T cell blasts in exponential growth for indefinite periods of time. Such purified T cell blasts do not respond to Con A, and the growth‐promoting activity in CM is independent of the mitogenic lectin used for its production. However, the appearance of activity in CM is Con A dose‐dependent. Furthermore, the production of these T cell growth factors is independent of B cells, while it requires both T cells and nontheta‐bearing, probably la‐positive cells present in normal and nude spleens. On the other hand, the T cell blasts which are reactive to the growth factors, neither produce CM by themselves nor can they cooperate with nude spleen cells for its production, in the presence of a mitogenic lectin. Since the concentration of growth factors in CM determines the extent of T cell growth, we propose that the growth of some T cells is necessarily dependent upon the activity in CM described here and, consequently, that the basis for T cell activation is the induction of such growth factors.