Interleukin-2 receptor expression in benign and malignant melanocytic skin lesions.

The immunophenotype of the lymphocytic reaction of melanocytic skin lesions (12 cases of cutaneous malignant melanoma (CMM), three of Hutchinson's melanotic freckle (HMF), and eight naevocellular naevi) has been studied using monoclonal antibodies. CMM was associated with the most intense lymphocytic reaction, the lymphocytes being T cells of both CD-4 T helper/inducer and CD-8 suppressor/cytotoxic subsets which were present in varying proportions. Although less marked, the lymphocytic reaction to HMF and benign naevi showed similar features. An antibody to the interleukin-2 receptor (IL-2R; Tac, CD-25) was included in the panel and the earlier findings of positively stained cells in association with CMM were confirmed. In addition, the novel finding of these cells in association with HMF and naevocellular naevi is reported. The number of these CD-25 positive cells was extremely variable but they appeared most prominent in association with CMM. The findings presented here indicate that it is not possible to infer that CD-25 positive lymphocytes present in the host response to CMM necessarily indicates tumour specific activation of the cells of the host immune system.