Background & objective: The anti-CD20 antibodies and fragments have been applied for treatment of non-Hodgkin's lymphomas (NHL) in clinic. The new anti-CD20 antibodies and their fragments (unmodified or radiolabeled) yet have been exploited for those patients with incomplete response to rituximab. The chimeric antibody fragments Fab and F(ab) '(2) derived from HI(47)(a mouse anti-CD20 antibody) have been constructed. The present study was designed to determine the effect of HI(47) and chimeric anti-CD20 antibody fragments on growth inhibition and apoptosis of lymphoma cells.
Methods: The binding of anti-CD20 antibodies to CD20 positive human B cell lymphoma Raji cells was examined using immunofluorescence assay. MTT method was used to evaluate the effect of chimeric antibody fragments on Raji cells growth. Annexin V staining and DNA ladder were used to examine the apoptosis of Raji cells induced by chimeric antibody fragments.
Results: HI(47) and its chimeric antibody fragments were capable of binding to CD20 positive Raji cells with the binding rate of above 90%. HI(47) did not compete with rituximab in binding with Raji cells. The growth of Raji cells was inhibited by HI(47) and its fragments with the inhibition rates of (57+/-1.5)%, (65.2+/-2.5)%,and (77.2+/-3.2)%, respectively, at the concentration of 100 microg/ml. The monovalent antibody fragment Fab (20 microg/ml) induced the apoptosis of Raji cells with early apoptosis rate of 17%.
Conclusion: The chimeric anti-CD20 antibody fragments derived from HI(47) have inhibitory effect on Raji cells and can induce apoptosis of Raji cells.