CHARACTERISTICS OF MHC ANTIGEN EXPRESSION AND TUMOR-INFILTRATING MONONUCLEAR-CELLS IN RENAL CELL ADENOMAS AND CARCINOMAS

We compared the expression of major histocompatibility complex (MHC; HLA class I and II) antigens and the presence of tumor-infiltrating mononuclear cells presenting S100 protein (S100), CD68 antigen, or CD45RO antigen in formalin-fixed, paraffin-embedded tissue sections of 10 renal cell carcinomas and 9 renal cell adenomas using immunohistochemistry. The expression of beta 2-microglobulin (B2MG) as an HLA class I antigen in all 10 cases (100%) and that of HLA-DR/alpha as an HLA class II antigen in 7 of 10 cases (70%) of carcinoma was stronger than that in the adjacent proximal convoluted tubule, but was respectively not different to weaker in 8 of 9 cases and not different to markedly weaker in all cases of adenoma. Furthermore, there was comparatively dense infiltration by S100(+) antigen-presenting cells in the carcinomas, but almost none in the adenomas and generally dense infiltration by CD45RO(+) T cells and CD68(+) macrophages in the carcinomas, but little to none in the adenomas. We concluded that the generally enhanced expression of MHC antigens in carcinomas must be an immnunophenotypic deviation from not only the adjacent proximal convoluted tubule but also adenomas, and that the predominant infiltration of antigen-presenting cells, T cells and macrophages in the carcinomas, but not in the adenomas, reflects the anti-cancer immune reaction