Current research on immunopathology of melanoma: analysis of lymphocyte populations in relation to antigen expression and histological features of melanoma.

Immunoperoxidase localization of monoclonal antibodies in sections of melanoma has been used to identify histological features which may be of prognostic importance in melanoma, in particular whether certain structures on melanoma cells may determine the degree and nature of lymphoid infiltrates and whether these may be related to prognosis. Monoclonal antibodies to lymphocyte subpopulations were used to identify and quantitate lymphoid infiltrates in 15 primary melanomas and 8 cutaneous metastases. These were correlated with histological features identified in routine sections. There was a wide variation in the numbers of mononuclear cells associated with both primary and metastatic melanoma. T cells and to a lesser extent macrophages accounted for the majority of the cells, B cells and natural killer (NK) cells for only 2% of the infiltrates. The Leu 3a (helper) T cell subpopulation predominated in primary tumours, OKT8 positive (suppressor/cytotoxic) cells in metastases. Infiltrates in which OKT8 cells predominated were associated with ulceration, a high mitotic rate and thick primary tumours. The converse applied to Leu 3a infiltrates. Infiltrates with a high proportion of Leu 3a positive cells tended to be associated with Thy-1 positive, DR antigen negative tumours. Thy-1 antigens were predominantly expressed on primary tumours and rarely on metastases whereas the converse applied to expression of the acute lymphoblastic leukemia antigen (CALLA) on melanoma cells. These findings suggest that certain melanoma antigens may be related to the nature of the lymphoid infiltrate associated with melanoma and possibly with the behaviour of the tumour in the host. They further suggest that identification of cell surface structures and lymphoid infiltrates by these techniques may be a valuable extension of routine histopathological assessment of prognosis in melanoma.