Immunological heterogeneity in human melanoma: immunogenic alloantigen expression in autologous host

A patient presented with a primary melanoma, Level IV, 2.5 mm thick; 30 excised lymph nodes were all negative for tumor. Four local recurrences followed in the ensuing 17 months. Tumor cells cultured at this time were epithelioid. Autoimmunization was followed by a disease-free interval of 15 months. Postimmunization, the patient's lymphocytes destroyed his melanoma cells in culture and were stimulated in mixed cell culture by his irradiated tumor cells. Cells grown from the relapsing tumor were spindle/dendritic with bizarre morphology and were not attacked by his lymphocytes in culture. Using a C' fixation technique, DR antigen profiles of the patient's B-cells and both tumor cell types showed that the immunizing tumor was positive for DR antigens 3, 5, and 8, none of which were present on his B-cells which had DR 2 and 4. Both B-cells and immunizing tumor cells were positive for DQ antigens. The relapsing tumor cells were positive for DR2 and negative for all other D region antigens tested. The evidence suggests that given a melanoma of heterogeneous cell population, autoimmunization against the predominant immunogenic cell inhibits tumor growth but allows the ascendance of a nonimmunogenic tumor cell type.