Decreased expression of HLA class II antigens on human uveal melanoma cells after in vivo X-ray irradiation.

In order to determine the presence of HLA antigens on human uveal melanomas, we tested anti-HLA monoclonal antibodies on tissue sections of these tumors. A great variety in expression of HLA class I and II antigens was present. A significantly lower expression of HLA class II antigens was present on uveal melanomas that had been irradiated before enucleation. These tumors lacked a lymphocytic infiltrate in comparison with nonirradiated tumors. These data suggest that radiotherapy affects expression of histocompatibility antigens on tumors.