Reduction of major histocompatibility complex class I antigens on invasive and high-grade transitional cell carcinoma

We examined immunohistologically the expression of major histocompatibility complex (MHC) class I and II antigens, which play important roles in immune reactions, on transitional cell carcinoma (TCC). When stained with monoclonal antibody W6/32 against class I antigens, reduced staining was observed in 34 of 46 TCCs and was virtually absent in 15 of these. The cases showing reduced staining were much more frequent (29 of 34) in high- to moderate-grade than in low-grade TCC. Furthermore, class I antigens were reduced in 18 of 19 invasive TCCs, but in 16 of 27 superficial TCCs. Thus, the reduction of class I antigens was correlated significantly with a decreased degree of tumour cell differentiation and the presence of invasion. Class II antigens on TCC showed variable expression and were not related to tumour grade or stage.