Effect of BCG on monocyte-mediated antibody-dependent cellular cytotoxicity in stage I melanoma

The functional activity of monocytes in human disease and the role of this particular cell type in host defense is a matter of current interest. Among several assays for monocyte function, an antibody-dependent cellular cytotoxicity microassay is regarded as a convenient test system in which monocytes of a Ficoll-Hypaque-separated mononuclear cell fraction act as effector cells and consequently lyse 51Cr-labeled, antibody-coated human erythrocytes. This assay was applied to a total of 35 individuals: 20 patients with Stage I melanoma and 15 healthy control subjects. All melanoma cases were treated by means of excision of the primary lesions and subsequent regional lymphadenectomy. Ten patients were selected at random and received additional adjuvant BCG immunotherapy for periods of 9.4 +/- 1.7 months. The mean percentage of 51Cr released in melanoma patients not receiving BCG was significantly lower (P less than 0.01%) than that in healthy control subjects. Monocyte numbers, as evaluated by means of nonspecific esterase staining, were not statistically significantly different.