Immunosuppressive activity and tissue polypeptide antigen content of human ascitic fluids

Ascitic fluids from patients with cancer, cirrhosis, and congestive heart failure and from a patient with noninfectious tuberculosis contain measurable levels of tissue polypeptide antigen (TPA). Only the cancer patients had levels higher than 2.0 microgram TPA per ml. The average TPA levels of 29 cancer patients was 6.4 microgram/ml compared to 0.9 microgram/ml for the controls. Seventeen of 22 cancer ascitic fluids and 7 of 9 fluids from patients with liver disease were immunosuppressive as measured by the inhibition of [3H]thymidine incorporation into phytohemagglutinin-stimulated lymphocytes. Fluids from a patient with congestive heart failure and a patient with noninfectious tuberculosis were not suppressive. We were unable to obtain a significant correlation coefficient between immunosuppression and TPA levels in these fluids. In addition, TPA levels remained constant over a period of 18 months of testing, whereas the in vitro immunosuppressive activity was lost in 9 to 10 months. Sephadex G-200 fractionation of the ascitic fluid resulted in the TPA and immunosuppressive activity eluting in the first large molecular weight peak from the column. Although the 2 activities eluted together in this fractionation, the data suggest that TPA is not responsible for the immunosuppression.