Synthesis of interleukin-1 alpha and beta by normal human melanocytes.

Normal human melanocytes and melanoma cells have been reported to produce several cytokines. Previously we demonstrated that neonatal human melanocyte proliferation and tyrosinase activity are inhibited by interleukin-1 alpha, tumor necrosis factor-alpha, and interleukin-6. We have now also shown that interleukin-1 beta induces an inhibiting effect on neonatal melanocyte tyrosinase activity with little effect on melanocyte proliferation. We investigated the ability of neonatal and adult human melanocytes to synthesize interleukin-1 alpha and beta. By immunocytochemistry, using monoclonal antibodies against interleukin-1 alpha and beta, we observed that neonatal and adult melanocytes stain positively for both cytokines. Flow-cytometric analysis revealed that the percentage of melanocytes positive for interleukin-1 alpha was always greater than that for interleukin-1 beta. The ability of neonatal and adult melanocytes to synthesize interleukin-1 alpha and beta was further confirmed using the polymerase chain reaction. These results clearly indicate that human melanocytes synthesize interleukin-1 alpha and beta, and that these cytokines may function as autocrine and/or paracrine regulators of cells in the epidermis.