Evidence for three binding sites for C3 (hemolytically inactive), C3b and C3d on a CR2-positive Burkitt lymphoma-derived cell line (Raji).

The present investigation shows that C3 (hemolytic inactive) as well as C3b and C3d bind Raji, a CR2-positive Burkitt lymphoma-derived cell line. Pretreatment of the cells with OKB-7 inhibited the binding of C3, whereas pretreatment with HB-5 inhibited the binding of C3b. Furthermore, the cells coated either with OKB-7 or HB-5 bound high amounts of C3d. TPA-treated cells showed binding for C3b and weak binding for C3 and C3d. Taken together, the data suggest that Raji cells may express three binding sites for C3, C3b and C3d which can be differently modulated by anti-CR2 MoAbs and TPA.