An immunohistological study of HLA antigen expression by gestational choriocarcinoma.

Two cases of gestational choriocarcinoma have been examined for the expression of HLA and trophoblast antigens using the indirect immunoperoxidase technique on frozen tissue sections. Approximately 40-70% of tumour cells express MHC Class I antigen as detected by a panel of antibodies to monomorphic, or framework, MHC Class I antigenic determinants. Evidence in one case suggests that most of these cells may not express the paternal, polymorphic HLA antigenic determinants but that a small subpopulation do carry the fully antigenically active molecule. These latter may give rise to patient anti-paternal HLA antibodies. Class II (HLA DR or DC) antigens are expressed by none, or very few, tumour cells.