Radiosensitive, thymic hormone-sensitive peripheral blood suppressor cell activity in cancer patients

Suppressor cell activity which was radiosensitive in most subjects and thymic hormone sensitive in some was identified in patients with cancer, and compared to simultaneously studied normal controls. Suppressor cell activity was measured in cocultures of normal lymphocytes with patient lymphocytes added in microwells using the blastogenic response to phytohemagglutinin and concanavalin A as the measure of activity. Thirty-five patients (lung cancer, 21; leukemia in remission, seven; and various solid tumors, seven) and an equal number of controls were studied. Suppressor cell activity was identified in 71% of the patients. In approximately 75% of these, the suppressor cell activity was radiosensitive (4000 to 6000 rads). For the phytohemagglutinin response, suppressor cell activity was thymic hormone sensitive in approximately 40% (Thymosin Fraction 5 or thymic humoral factor), and for the concanavalin A response, it was thymic hormone sensitive in about 25% of the cases. There was a significant correlation between the presence of immunodeficiency (defined as a phytohemagglutinin response < 35,000 or a concanavalin A response < 12,000 cpm) and the presence of the suppressor cell activity. The suppressor cell activity was heterogenous relative to its radiosensitivity and thymic hormone sensitivity. Suppressor cell activity was observed in all the patient categories. These results indicate that certain available therapeutic manipulations may have significant effects on suppressor cell activity and should be an important subject for further investigation.