[Mouse melanoma antigen immunological properties, structure and genes]

The immunological and chemical properties of melanoma antigens have been analysed by using C57BL/6-derived B16 melanoma cells. CTL was easily induced by the antigen of the melanoma cell surface, whereas soluble antigens secreted into the culture supernates worked as a specific inducer substance of suppressor T cells. Using two syngeneic monoclonal anti-melanoma antibodies (M2590, M562), we found that the melanoma antigen was composed of GM3 (NeuAc) in association with proteins with molecular weights of 31K, 58K and 80K. M2590 detected GM3, whereas M562 recognized the protein determinant. Finally, we succeeded in cloning the genomic DNA which codes for the melanoma antigen. The B16-melanoma cosmid libraries were constructed with the shuttle vector pCV103. They were infected into ED8767 E. coli and then transfected into human P36 melanoma by protoplast fusion. The transfectants were selected in the presence of mycophenolic acid, strained with FITC-M562, and selected by FACS. Total DNA was isolated from the transfectants, and the B16 genomic clones were rescued from the M562+ transfectants by in vitro packaging with lysogenic bacterial extracts. pD2-7 (34.8kb) reproducibly expressed M562 determinants in P36 human melanoma.