DETECTION OF TUMOR-NECROSIS-FACTOR SOLUBLE RECEPTOR-P55 IN BLOOD-SAMPLES FROM HEALTHY AND ENDOTOXEMIC HUMANS

The tumor necrosis factor (TNF) soluble receptor derived from the cell surface p55 TNF receptor (TNFsRp55) is a naturally occurring substanc e generated during infection and inflammation. TNFsRp55 inhibits biolo gic effects of TNF. An RIA was developed to quantitate TNFsRp55 in hum an blood. Recovery of TNFsRp55 from blood anticoagulated with EDTA was optimal compared with recovery from serum or heparinized plasma. TNF did not interfere with the assay. With the RIA based on radiolabeled n onglycosylated Escherichia coli-derived recombinant TNFsRp55, a mean c oncentration of 198 +/- 15 pg/mL was found in 14 volunteers. When glyc osylated CHO cell-derived TNFsRp55 was used, the mean level was 1656 /- 95 pg/mL. Infusion of endotoxin into volunteers induced TNFsRp55, w hich peaked at 517 +/- 99 pg/mL for the E. coli-based RIA and 7300 +/- 1810 pg/mL for the CHO cell-based RIA. These findings demonstrate tha t blood collected in EDTA is optimal for measuring circulating TNFsRp5 5 and that this soluble receptor is present in health but elevated dur ing endotoxemia.