HLA-DR histocompatibility leukocyte antigens permit cultured human melanoma cells from early but not advanced disease to stimulate autologous lymphocytes.

HLA-DR histocompatibility antigens are commonly expressed by the melanocytes of melanoma and its precursors, but not by the melanocyte of normal skin. Further, the primary lesion of biologically early melanoma is commonly infiltrated with host T cells. Advanced disease is characterized by a paucity of such cells. To investigate the interaction of melanoma cells and autologous lymphocytes and its dependence on HLA-DR expression, we have established cell lines from biologically early (4 lines) and advanced disease (11 lines) and examined their capacity to stimulate blastogenesis of autologous T cells in vitro. Melanocytes from early disease expressed HLA-DR antigens and stimulated autologous T cells. Those from advanced disease, irrespective of DR expression, were nonstimulatory. To determine whether expression of DR was required for melanoma cells to be stimulatory, we first treated a stimulating cell line of DR3 allospecificity with anti-DR3-specific serum and demonstrated marked inhibition of its capacity to provoke blastogenesis. Next we used fluorescence-activated flow cytometry to sort a stimulating line heterogeneous for DR expression into DR-enriched and -depleted populations. When such cells were examined in the lymphocyte proliferation assay, their stimulatory capacity was proportional to their quantitative expression of HLA-DR. These studies indicate that cell lines may reflect important biological differences between early and advanced melanoma. HLA-DR expression may be an early event in neoplasia of melanocytes. These antigens are able to interact directly with autologous T cells; and their expression is necessary, but not sufficient, for melanoma cells to induce lymphocyte proliferation.

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