Radioimmunoassay of free thyroxine with prebound anti-T4 microcapsules.

Free thyroxine (FT4) may be one of the active throid hormones in contact with target end organs. It is unaffected by alterations in serum protein levels. In most cases, measurement of FT4 reflects an individual's true thyroid function or dysfunction. Previous FT4 assay techniques have been difficult, tedious, indirect, and inaccurate. A rapid, simple, and accurate radioimmunoassay for FT4 has been developed using microencapsulated rabbit anti-T4 antiserum to which I-125 T4 tracer of high specific activity has been complexed. Addition of FT4 standards or unknown samples displaces a proportional amount of I-125 T4 from antibody. Protein-bound T4 is excluded from the reaction by short incubation time and spatial configurations. Specimens representing known thyroid dysfunction were tested using the above procedure. The normal range of FT4 was 0.8-2.4 ng/dl. The mean FT4 for the hyperthyroid group was 6.92 +/- 1.38 (range 4.4-9.6) ng/dl. The mean FT4 for the hypothyroid group was 0.43 +/- 0.37 (range 0.1-1.3) ng/dl, and in pregnancy the mean FT4 was 1.64 +/- 0.44 (range of 1.0-2.2) ng/dl (1).

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.