Sequential examination of lymphocyte proliferative capacity in patients with malignant melanoma receiving BCG immunotherapy.

A series of 42 patients with malignant melanoma treated with BCG adjuvant immunotherapy were studied for sequential changes in cellular immune reactivity to non-specific mitogens. Lymphocyte preparations were made monthly and stored in a viable condition in liquid nitrogen. After 6 months of treatment, all lymphocyte samples from an individual were recovered and tested for DNA synthesis after stimulation with PHA, PWM, Con A, PPD and MLC. The responses to the mitogens in the blastogenesis test were stable during the course of therapy. The MLC response did not increase significantly in patients treated with tumor-cell vaccines, and declined sharply in the six patients who subsequently relapsed and died. The in vitro PPD response increased 1 to 3 months after initiation of BCG in patients who were initially unresponsive to PPD in vitro. However, PPD-positive patients did not show any significant alteration of the PPD response. The PPD response did increase less sharply in patients whose disease eventually recurred than in those who remained without evidence of clinical disease. BCG therapy does not appear to correct lymphocyte proliferative defects in melanoma patients. Of the assays employed, the MLC and PPD tests appear to be the most useful as monitors of clinical status and response to therapy.