Effect of interferon-alpha on CD20 antigen expression of B-cell chronic lymphocytic leukemia

Chimeric CD20 monoclonal antibody as alternative therapy in relapsed low-gr ade non-Hodgkin's lymphoma (NHL) has produced responses in nearly 50% of pa tients. Augmenting CD20 expression on tumor cells and/or inducing its expre ssion may increase the cell kill and effectiveness of antibody therapy. Per ipheral blood lymphocytes from 19 patients with B-cell chronic lymphocytic leukemia (B-CLL) were incubated in vitro in the presence of interferon-alph a (IFN-alpha) (500 U/ml and 1000 U/ml) for 24 and 72 hours. The effect on C D20 expression was studied by flow cytometry. The differences in the percen tage positivity, the mean fluorescence intensity (MFI), and the product of percentage positivity and MFI were used to assess upregulation. There was a significant upregulation of CD20 expression on B cells seen at both concen trations after 24-hour priming (p < 0.01). B-CLL cells cultured for 72 hour s in the presence of IFN-<alpha> also showed upregulation of CD20 expressio n; however, the degree of upregulation was much lower than that seen at 24 hours. There was no statistically significant increase in CD20 antigen expr ession on normal lymphocytes following cytokine exposure. These results sug gest that IFN-alpha priming may augment the effectiveness of antibody thera py by directly upregulating CD20 antigen expression in addition to its indi rect action through effector cells of the host.