Early supernatants of mitogen-stimulated mononuclear cells promote long-term IL-2-dependent growth of human T lymphocytes.

Human wheat germ agglutinin (WGA)- or PHA-activated T lymphocytes from either peripheral blood or normal spleens can be propagated in vitro for several months in the presence of IL-2 but not IL-4 when periodically restimulated with supernatants collected from 24 h cultures of mitogen-stimulated human blood or spleen mononuclear cells. Following several rounds of stimulation with these supernatants some of the spleen-derived T lymphoblast lines acquire the ability of continuous growth (over 100 population doublings) in the presence of IL-2 alone. We postulate that the ability of 24 h supernatants from mitogen stimulated mononuclear cells to maintain T lymphoblast IL-2-dependent growth depends upon yet undefined cytokine(s) released early after activation.