Lack of suppressive activity of human primary melanoma cells on the activation of autologous lymphocytes

Previous studies have indicated that primary but not metastatic melanomas were able to stimulate the proliferation of autologous (Auto) peripheral blood lymphocytes (PBL) in 73% of cases. On the other hand, 57% of the metastatic melanomas were shown to be suppressive when melanoma cells (Me) were admixed with Auto-PBL stimulated with allogeneic (Allo) PBL or interleukin 2 (IL-2) at the beginning of a 6-day incubation period. Here, we report that the suppressive activity of Me is a functional characteristic associated with a particular stage of the disease. In fact, we found that none of the 11 primary tumors tested were able to inhibit the proliferative response of Auto-PBL to Allo-PBL or IL-2 at all the doses of tumor cells used. The generation of lymphocytes cytotoxic against Auto-Me or K562 was also not inhibited. Of the 11 primary tumors checked for suppression, 8 were able to stimulate Auto-PBL in a primary mixed lymphocyte tumor culture. We conclude that opposite functions, stimulation and inhibition of autologous lymphocyte responses are characteristics of primary and metastatic Me, respectively.