Specific Inhibition of Lymphocyte Blastogenic Responses to Mitogens by a Factor Produced by Cultured Human Malignant Lymphoma Cells

A glass-adherent human lymphoma cell line was found to produce an inhibitor of human in vitro lymphocyte blastogenic responses. The responses to mitogens, antigens, and allogeneic leukocytes were inhibited over 90%, as assayed by DNA synthesis or morphology. The effect was not associated with cytotoxicity and was reversible by washing the inhibited cells. The material was a nondialyzable, heatstable protein. Its activity was not affected by its deoxyribonuclease and ribonuclease but was destroyed by Pronase. Most important, the inhibitor was species and tissue specific; it did not inhibit mouse lymphocytes or a variety of human tissue culture cell lines. The relationship of this material to regulation of lymphoid function and to the etiology and pathogenesis of cancer is discussed.