Lymphocyte chalone concentrates and their effects upon leukemic cells in vitro.

Lymphocyte chalone is a cell-specific but not species-specific noncytotoxic and endogenous inhibitor of the transformation and mitotic activity of normal lymphocytes stimulated in vitro by either lectins or antigens. However, human- and mouse-established lymphoblastic cell lines were killed and their uptake of thymidine was inhibited after incubation for almost one complete mitotic cell cycle. The chalone lymphocytotoxicity effect was also demonstrated, using primary cultures of EL-4 lymphoma cells. Lymphocyte chalone was highly cytotoxic to leukemic cells under crowded condition (cells in G1-G0) in contrast to S phase chemotherapeutic agents. Finally, thymus chalone lymphocytotoxicity appears to be specific for T versus B lymphoblastic cell lines.