A radioimmunoassay and biological profile of Ia-like antigens on human melanoma cells.

Human melanoma cells have unexpectedly been found to express Ia-like antigens, histocompatibility type antigens which are believed to be the gene products of the immune response region. Melanoma derived Ia-like antigens are immunologically functional. Monoclonal antibodies have been produced to these antigens. The level of Ia-like antigens on melanoma cells is significantly lower than on B lymphoid cells, and this is more likely to reflect a reduced synthesis than an increased shedding. We have employed radioimmunometric and immunofluorescent procedures in this investigation, Melanoma cell-derived Ia-like antigens have a structure similar to that of B lymphoid cell-derived Ia-like antigens. The antigens are composed of two non covalently associated glycoproteins. One chain, referred to as the alpha chain, has an approximate molecular weight of 34,000 and the other one, referred to as the beta chain, has an approximate molecular weight of 29,000. The expression of Ia-like antigens is restricted to malignant melanoma and not on benign nevi.