Modulation of B16 melanoma antigen expression by lymphokines and dimethyl sulfoxide.

We have developed two monoclonal antibodies, designated 152 E12 D7 and 153 C7 A6, which have reactivity with cell surface antigens expressed on the B16 mouse melanoma. These monoclonal antibodies are produced by hybridomas resulting from the fusion of splenocytes taken from C57BL/6 mice bearing the B16-F10 tumor. The monoclonal antibodies are of the immunoglobulin M class and have been shown to react with three variants of the B16 and another mouse melanoma but no normal murine tissues. Exposure of B16 melanoma cells to a concanavalin A stimulated spleen cell mixed lymphokine preparation (LK) and to dimethyl sulfoxide (DMSO) enhanced the expression of the cell surface antigens recognized by these monoclonal antibodies. The cultures stimulated with LK or DMSO contained a greater proportion of cells expressing the antigens recognized by monoclonal antibodies 152 E12 D7 and 153 C7 A6 than did unstimulated controls. In addition to increasing the proportion of antigen-positive cells, the antigen expression per cell, as measured by fluorescence intensity, was substantially increased following exposure to LK and DMSO. The effects of treatment with LK or DMSO were apparent after 24 h exposure but did not persist after the agent was removed from the cultures, suggesting that the enhancement of antigen expression was a transient event rather than a permanent differentiation of the melanoma cells.