Serum immunosuppression test as a new tool for immunodiagnosis of lung cancer

The immunosuppressive activity of serum from lung cancer patients on the anti-sheep red blood cell plaque-forming cell response in mouse spleens was evaluated by an in vivo technique in 64 patients with lung cancer and in a control group composed of 53 patients with a variety of nonmalignant disorders and 15 healthy adults. When immunization with sheep red blood cells was done on Day 5 after serum injection, the frequency of immunosuppression by serum from lung cancer patients [50 of 64 (78%)] was significantly higher than with serum from patients with nonmalignant diseases [3 of 53 (6%); p less than 0.025] or from healthy adults [1 of 15 (7%); p less than 0.005]. In serum from lung cancer patients, there was no correlation between the serum immunosuppressive activity and histological classification. However, sera from Stage II patients showed a relatively high frequency of suppression [25 of 27 (93%)] compared with sera from the Stage I group [7 of 14 (50%); p less than 0.005]. In experiments examining the transfer of plaque-forming cell-suppressive activity, tests using 10(7) thymus cells and more than 10(5) spleen cells from mice given injections of lung cancer serum indicated that suppressive action is mediated by the generation of suppressor cells by lung cancer serum. The clinical use of this test in diagnosis and immunological studies of lung cancer is discussed.