Analysis of the NIH workshop monoclonal antibodies to human melanoma antigens

Reagents exchanged at the 2nd workshop on monoclonal antibodies (MoAb) to human melanoma antigens were analyzed using both serological and immunochemical assays. The analysis by laboratories participating in the workshop of our MoAb 225.28S, 345.134S, 376.96S, 465.12S, and 763.24TS reaffirms our own analysis of these reagents in that (1) they all react with the majority of melanoma cell lines tested and (2) the reactivity of MoAb 225.28S and 763.24TS is much more restricted than that of MoAb 345.134S 376.96S, and 465.12S. Our serological analysis revealed that the majority of workshop reagents reacted with cultured melanoma cells. Immunochemical analysis of these monoclonal antibodies allowed for their division into three groups according to the molecular weights of the antigens recognized in immunoprecipitation experiments, greater than 100 kd, 80-100 kd, and DR antigens. Further analysis of the first two groups of monoclonal antibodies by immunodepletion and antibody binding inhibition assays revealed that MoAb 9.2.27, 225.28S, and 763.24TS recognize distinct determinants with a heterogeneous distribution on subpopulations of a high molecular weight melanoma associated antigen. MoAb 376.96S and 705.F6 recognize either the same or spatially close determinant(s).