Abstract
Complement‐dependent cytotoxicity against melanoma cells was demonstrated with a microassay in sera from melanoma patients. The response was tumor‐specific and histologic type‐specific since 16 out of 52 (30%) melanoma patient sera taken before surgery reacted against melanoma cells, whereas 3 out of 43 (7%) control sera, collected from patients with unrelated tumors and from cancer‐free individuals, were positive. The serum activity correlated with the clinical stage of the disease since it was detected in 15 out of 40 patients with stage I and II tumors and in 1 of the 12 patients in stage III. Twelve melanoma patients, clinically tumor‐free for 1 to 4 years after surgery, showed no humoral cytotoxicity. A follow‐up study of 13 melanoma patients revealed that the cytotoxicity appeared 7‐10 days after radical removal of the tumor and that it disappeared if there was no recurrence. The histologic type‐specificity was further tested by assaying sera from 16 melanoma and 10 breast‐cancer patients simultaneously on both melanoma and breast‐cancer cells; a positive reaction was observed in 6 cases of melanoma and in 5 of breast cancer on homologous cells only, in 1 case on the opposite type of cells, and in 3 cases on both types of tumor cells.