Alloreactive cloned T cell lines. VII. Comparison of the kinetics of IL 2 release stimulated by alloantigen or Con A

A cloned T amplifier cell, designated L2, was shown previously to release several lymphokine activities, including IL 2, following stimulation with either alloantigen or concanavalin A (Con A). However, the responses induced by the two stimuli differ significantly. When high numbers of L2 cells were stimulated with Con A, greater amounts of IL 2 were released whereas stimulation of high numbers of L2 cells with alloantigen resulted in the release of less than optimal levels of IL 2. IL 2 levels as high as 1500 units/ml were reached with Con A. When stimulated with alloantigen, the release of L2 cells was followed by proliferation. When stimulated with Con A, the cells did not proliferate. The inhibitory effect was related to the length of exposure of L2 cells to the lectin and could be avoided by removing the excess Con A from cultures 3-6 hours after stimulation. Thus, a brief exposure of L2 cells to Con A was sufficient to cause the release of high levels of lymphokine activities and permit the L2 cells to proliferate in a pattern similar to that after stimulation with alloantigen. These results are consistent with the hypothesis that the lectin, Con A, acts as a mitogen for cloned murine amplifier T cells only indirectly by triggering the release of growth factors which then promote cell proliferation.