Mixed lymphocyte--tumor cell culture reaction in cancer patients

To measure immunological reactivity or recognition of tumor antigens, mixed lymphocyte--tumor cell culture reaction (MLTR) was studied using a micromethod. The peripheral lymphocytes of cancer patients were mixed in vitro with autochthonous tumor cells that had been irradiated with 60Co at a dose of 6,000 rad just before use. The lymphocyte blastogenic response was estimated by the incorporation of 3H-thymidine in the acid-insoluble fraction and expressed as counts per minute. The stimulation index equal to or greater than 2.0 was arbitrarily expressed as positive blastogenic response in the present experiment. Positive blastogenic responses to autochthonous tumor cells were observed in 10 of 34 patients with various solid tumors. The intensity of blastogenic response to tumor cells was correlated with that of the non-specific responses to PHA (r=0.4732, P less than 0.01). These results indicated that non-self tumor-associated antigens, which could induce in vitro blastogenic response of autologous lymphocytes, were present in some part of human tumors.