Sequential studies on cell‐mediated tumor immunity and blocking serum activity in ten patients with malignant melanoma

Ten human patients with malignant melanoma were followed with respect to two in vitro parameters of tumor immunity, the ability of the patients' blood lymphocytes to destroy cultivated melanoma cells, and the ability of the patients' sera to block such destruction, and with respect to changes in the clinical status, such as increases or decreases in detectable tumor mass. Allogeneic and (to a much lesser extent) autochthonous melanoma cells were used as targets. The degree of lymphocyte‐mediated tumor immunity was higher in patients with little or no residual tumor than in patients with large tumor loads, although the latter patients were also found to be reactive. Sera from patients with clinically detectable melanoma could block the cytotoxic lymphocyte effect, as could sera from patients who developed melanoma shortly after the serum harvest. Disappearance of blocking serum activity was seen to accompany clinical improvement. Sera from some patients without clinically detectable tumor could potentiate the cytotoxic effect of lymphocytes from melanoma patients. The findings support the view that cell‐mediated tumor immunity and blocking serum activity, as studied in vitro , are important correlates of the patients' immunological defense against their tumors in vivo , and they suggest that monitoring of these parameters may be prognostically useful. They also suggest that procedures capable of improving cell‐mediated tumor immunity without increasing blocking serum activity may be therapeutically beneficial.