IDENTIFICATION WITH MONOCLONAL-ANTIBODY-140.240 OF A STRUCTURAL VARIANT OF MELANOTRANSFERRIN SHED BY HUMAN-MELANOMA CELL-LINES IN-VITRO

Shedding by cultured human melanoma cells of a well-characterised cell -surface glycoprotein antigen known as ''melanotransferrin'' was studi ed with two monoclonal antibodies, 140.240 and 96.5. By means of [S-35 ]-cysteine metabolically-labelled melanoma cells and immunoprecipitati on studies, identification was made, by 140.240 in the spent media of Two of six melanoma cell lines, of a new molecule of 100-kDa, aside fr om the 88-kDa molecule. Only the 88-kDa shed molecule was detected in the remaining four melanoma cell lines with both antibodies. None of n ine clonal sublines derived from the two melanoma cell lines were foun d to shed the 100-kDa ol 88-kDa molecule exclusively. Both shed antige ns were released spontaneously to the medium from the live melanoma ce lls rather than as a result of cell death and lysis; since there was n o obvious cell death ol debris in the spent medium nor in the monolaye r cells detected at the time of spent medium collection.