PROLIFERATIVE RESPONSE OF B-CHRONIC LYMPHOCYTIC-LEUKEMIA LYMPHOCYTES STIMULATED WITH IL2 AND SOLUBLE CD23

The in vitro proliferative response of purified B-chronic lymphocytic leukemia (B-CLL) lymphocytes cultured in the presence of soluble CD23 (sCD23) with or without IL2 was compared to the responses induced by p horbol 12-myristate 13-acetate (PMA), Staphylococcus aureus strain Cow an I (SAC), IL1, IL2, IL4, IL6 and the combination of IL2 and interfer on (IFN) cu or IFN gamma. As expected, B-CLL lymphocytes proliferated with PMA, SAC and IL2 with a clear enhancement of the IL2-induced resp onse by IFN alpha or IFN gamma. They failed to proliferate in response to sCD23, IL1, IL4 or IL6 alone nor to the combinations of sCD23 and any of the 3 latter cytokines. However, sCD23 significantly increased the proliferation of B-CLL cells induced by IL2, suggesting a protecti ve effect of sCD23 on apoptosis. Serum levels of sCD23 and CD23 membra ne expression were high in every patient which is compatible with the hypothesis of an autocrine or paracrine activation loop. Detectable CD 23 expression was lost in all cultures except for that stimulated by P MA. Only supernatants of PMA-stimulated cultures contained high sCD23 levels.