INHIBITION OF LEUKEMIC-CELL PROLIFERATION BY FACTOR(S) RELEASED FROM IRRADIATED LYMPHOCYTES OF B-CHRONIC LYMPHOCYTIC-LEUKEMIA PATIENTS

An attempt was made to clarify the mechanism by which splenic irradiat ion in patients with B-chronic lymphocytic leukemia (B-CLL) can induce a reduction in lymph node size. For this purpose peripheral blood lym phocytes from B-CLL patients were exposed to cobalt irradiation and we re cultured for 1-8 days. The effect of the supernatants on the prolif eration capacity of normal and malignant human cells was examined. A s uppression of phytohemagglutinin (PHA)-induced proliferation of autolo gous and heterologous B CLL lymphocytes was observed, whereas there wa s no effect on the proliferation of lymphocytes obtained from healthy volunteers. In addition, supernatants of irradiated B-CLL lymphocytes inhibited thymidine incorporation into blasts derived from patients wi th acute leukemia and the lymphoblastoid cell line Daudi, but they did not exert any effect on normal cells obtained from human embryonic li ver. These results suggest the secretion of some factor(s) by irradiat ed B-CLL lymphocytes, which may inhibit the proliferation of malignant cells but has no effect on normal cells. (C) 1994 Wiley-Liss, Inc.