Two Human Monoclonal Antibodies Reacting with the Major Gangliosides of Human Melanomas and Comparison with Corresponding Mouse Monoclonal Antibodies1

The fine specificity analysis of two human monoclonal antibodies (AbFCMl and Ahi UM I ) reacting with gangliosides is described and their specificities are compared with analogous mouse monoclonal anti bodies (mAt)s). These two antibodies were generated from lymphocytes of melanoma patients by Epstein-Barr virus transformation followed by fusion with mouse myeloma NS-1. Using a wide variety of gangliosides, including yV-glycolylneuraminicacid (NeuGc)-containing compounds, the precise structures recognized by these two antibodies were elucidated by enzyme-linked immunosorbent assay and immunostaining of thin-layer chromatograms. AbFCMl reacted with /V-acetylneuraminic acid (NeuAcMype CMS, GDI», sialylparagloboside, and (.¡„, in decreasing order of intensity. This antibody also reacted with (NeuAc-NeuGc-)-Go3 and -disialylparagloboside, but did not react with NeuGc-type GMJ,GMZ, sialylparagloboside, (NcuGc):-< «in and -disialylparagloboside. The main epitope structures recognized by AbFCMl are, therefore, NeuAca2—» 3Gal/31and NeuAca2-»8NeuGca2—»Gal/31-. These results are similar to the specificity of mouse mAb M2S90. AbHJMl reacted with NeuActype GDSand disialylparagloboside, GDZ,GDII» GM.I. and G, n„ in decreas ing order of intensity. Among NeuGc-type gangliosides, this antibody reacts with (NeuAc-NeuGc-)-Go3 and -disialylparagloboside, but did not react with gangliosides containing only NeuGc. Consequently the epitope structure recognized by AbHJMl is probably (R)-(Neu\ca2—»SSialic acida2—»3)Gal/31-. Mouse anti-Cm mAbR2<4,in contrast, showed strong reactivity only with Gn< and -disialylparagloboside among NeuAc-type gangliosides, but showed a similar pattern to AbHJMl in its reactivity with NeuGc-containing gangliosides. Although these two human mono clonal antibodies are not highly restricted in their specificities, they reacted best with the major gangliosides, GMJ and Gm, present in the majority of human melanomas.