Modulation by MHC class I antigens of the biology of melanoma cells. Non-immunological mechanisms.

Many human as well as experimental tumours, including melanoma, express reduced levels of major histocompatibility complex (MHC) Class I antigens. Decreased MHC Class I antigen expression may be selected during neoplastic progression because it allows tumour cells to escape killing by cytotoxic T lymphocytes. Furthermore, the regulatory role of MHC Class I antigens in the proliferation of T cells suggests that abnormalities in MHC Class I antigen expression may play a role in the disordered proliferation of malignant cells and in their metastatic potential by non-immunological mechanisms. This paper reviews some of the available evidence supporting the concept of non-immune functions of MHC Class I antigens in the biology of malignant cells, with emphasis on experimental models for metastatic melanoma.