Immunoregulatory factors from a human macrophage-like cell line. II. A human T-cell lymphokine-induced suppressor factor for lymphocyte proliferation.

It has been demonstrated that the human histiocytic lymphoma-derived cell line U937, which has monocytoid characteristics, responds to a concanavalin A-induced T-cell-derived suppressor supernatant (T-SFS) with the release of a factor markedly suppressing mitogen-stimulated proliferation of normal peripheral blood lymphocytes. The suppressor material is not dialyzable, appears within 2 hr of exposure of U937 cells to the T-SFS, persists for at least 24 hr, and has a Mr of approximately 40,000 by gel chromatography. The suppressor factor does not affect the proliferation of continuous T- and B-lymphoid cell lines, distinguishing it from the inhibitor of DNA synthesis also released by U937, but appears to be specific for a stage of activation of normal lymphocytes that is independent of (a) utilization of interleukin-2 and (b) inhibition of production of interleukin-2.