Expression of DR antigens in freshly frozen human tumors

DR antigens are thought to function as differentiation antigens and to restrict immune recognition between T cells and B cells, monocyte/macrophages, Langerhan's cells, and endothelial cells. These antigens are commonly found on tissue culture lines from metastatic melanomas and tumors of lymphocyte derivation but are notably uncommon on cell lines from other malignancies. Using frozen tissue sections, a monoclonal antibody (WI 691-13-17) known to detect an epitope common to all DR alloantigens on the beta (light) chain of DR antigens, and a two-step indirect immunoperoxidase technique, DR antigens were found on all metastatic lesions tested and on many primary tumors and their histogenetic precursors. The technique of using monoclonal antibodies in indirect immunoperoxidase staining of freshly frozen tissue allows individual cells to be assessed for antigen expression and presumably more accurately reflects in vivo antigen expression than results obtained from cells selected by tissue culture methods.