Immunosuppressive factors in ascites fluids from ovarian cancer patients.

The nonspecific immunosuppressive effect of ascites fluids from ovarian cancer patients was examined and compared with that of noncancerous abdominal effusion and sera from ovarian cancer patients. The malignant ascites fluids produced a noncytotoxic, dose-dependent suppression of DNA synthesis of phytohemagglutinin-stimulated human peripheral blood lymphocytes. The suppression was higher than that observed in sera from cancer patients. No suppressive effect was seen in control abdominal effusion. The factors responsible for inhibition of in vitro lymphocyte function were partially purified from ascites fluid by lentil lectin affinity chromatography and gel filtration. Major active factors had a high molecular weight (440-1500 kilodaltons), an affinity to lentil lectin, and were stable against heat and acid treatment.