Effects of recombinant interferon-alpha and -gamma on B-CLL cells in serum-free medium: expression of activation, differentiation, and CALLA antigens.

Chronic B-lymphocytic leukemia (B-CLL) cells from 10 patients were cultured serum-free with recombinant interferon (rIFN)-alpha 2, rIFN-gamma, or phorbol ester (TPA) for 5 days. All three agents induced functional differentiation, as evidenced by IgM secretion, without concomitant proliferation. A panel of monoclonal antibodies was used to detect changes in cell surface antigens defining pre-B cells (CALLA), resting B cells (HH1), early (4F2, MHM6) and late (anti-Tac, OKT9) B cell activation, and terminally differentiated B cells (OKT10). The activation markers 4F2, MHM6, and anti-Tac and the plasma cell marker T10 were all significantly induced with TPA, rIFN-alpha 2, an rIFN-gamma, whereas the expression of HH1 decreased. CALLA was detected on substantial proportions of differentiated (4-38%) but not resting (0-4%) B-CLL cells. The CALLA-positive B-CLL cells were negative for nuclear terminal deoxynucleotidyl transferase (TdT). The T9 antigen was expressed on TPA-treated cells (1-16%) only. The present findings indicate novel properties of IFN-alpha and IFN-gamma in inducing terminal differentiation of human monoclonal B cells without prior activation.