Activation of Complement (C) in Human or Animal Serum by Lymphoblastoid Cell Lines Derived from Patients with Burkitt's Lymphoma (BL) and Infectious Mononucleosis (IM)

Abstract

Abstract Several lymphoblastoid cell lines derived from patients with BL or IM were tested for C3b receptors by the rosette-forming technique using EAC3b. When the cells which possessed C3b receptors (Raji and IM) were incubated in normal human serum (NHS) the C receptor activity was inhibited. This was not found with other C3-rosetting cells such as peripheral blood lymphocytes from normal donors (PBL) or from patients with chronic lymphatic leukemia (CLL) or macroglobulinemia (MG). The blocking of the C receptor did not appear to be caused by native C3 since neither EDTA-plasma nor purified human C3 inhibited rosette formation (RF). Instead, inhibition was accomplished with C3b and with EDTA-plasma supplemented with Mg++ (EGTA-Mg-plasma). Deposition of C3 on membranes, assayed by direct immunofluorescence using F(ab′)2 anti-human C3, was seen on all the cells tested except PBL, CLL, or MG cells, only after incubation with NHS, suggesting that positive cells activated C. Staining was also observed when the prior incubation was performed with EGTA-Mg-plasma but not when purified C3 or EDTA-plasma were used.