Galactosylation of human IgG monoclonal anti-D produced by EBV-transformed B-lymphoblastoid cell lines is dependent on culture method and affects Fc receptor-mediated functional activity.

Human monoclonal antibodies to the Rh D blood group antigen were produced by EBV-transformed B cell lines grown in serum-free medium in low density (LD) static cultures or high density (HD) hollow fiber bioreactors. Glycosylation analysis of the purified IgG was determined by the binding of anti-GlcNAc monoclonal antibody (GN7) and by analysis of oligosaccharides released by hydrazinolysis. The LD MAbs had only trace levels of agalactosyl oligosaccharides (G0), the major species (> 70%) being digalactosyl structures (G2). The HD MAbs, by contrast, contained about 10% G0 and relatively high levels (over 50%) of monogalactosyl (G1) oligosaccharides. beta 1-4 galactosyltransferase activity in the LD cell lines was similar to that found previously for other EBV-transformed B cell lines. The predominant oligosaccharides of an IgG3 anti-D, BRAD-3, contained bisecting N-acetylglucosamine. In functional assays with Fc receptor (Fc gamma R) positive effector cells, the highly galactosylated LD form of BRAD-3 was more active than the HD form in monocyte (Fc gamma RI) and K cell (Fc gamma RIII) mediated lysis of erythrocytes in ADCC assays, although these preparations showed no difference in Fc gamma RI-mediated rosette formation with U937 cells. One MAb, JAC10, was over 10-fold less active than two other IgG1 MAbs, 2B6 and BRAD-5, at mediating lysis of erythrocytes by Fc gamma RIII+ K cells; differences in sialylation may have contributed to this heterogeneity.(ABSTRACT TRUNCATED AT 250 WORDS)