RELATIONSHIP OF MELANOMA-ASSOCIATED ANTIGENS TO HISTOCOMPATIBILITY ANTIGEN AND β-2 MICROGLOBULIN IN MATERIAL SPONTANEOUSLY SHED BY CULTURED HUMAN MELANOMA CELLS

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Abstract
With monkey antisera, melanoma-associated antigens (MAA) on cultured and fresh human melanomas that crossreact with antigens on retinoblastoma and gliblastoma have been described. When these MAA, which can be recovered in the spent medium of cultured melanoma cells, were subject to centrifugation through KBr, they were found by serological assays using monkey anti-MAA to be concentrated in the top fraction. Melanoma antigenic activity detected by the leukocyte adherence inhibition (LAI) blocking assay was also found only in the top fraction of the KBr preparation. Passage of the concentrated spent culture medium containing MAA, HLA-A10 and HLA-DR antigens over an anti-.beta.2 microglobulin affinity column resulted in binding of MAA and the histocompatibility antigen to the column, although no retention of HLA-DR antigen could be demonstrated. The shed MAA, which are defined by monkey antiserum and by their reactivity in the LAI blocking assay, are similar to histocompatibility antigens in terms of flotation on KBr and association with .beta.2 microglobulin. Other findings, which are not entirely in accord on this subject are discussed, the differences are thought to be due, in part, to the definition of MAA in various reports. The current heterogeneity of putative MAA will have to be further defined to determine which MAA have structural, and possibly functional, similarities to histocompatibility antigens.