Abstract
The present study was designed to evaluate the influence of obstructive jaundice on human natural killer (NK) cell activity and to elucidate the mechanism whereby this influence is exerted. In 7 clinical cases of jaundice the serum levels of 4 bile acids, i. e., glycocholic acid (GCA), taurocholic acid (TAC), glycochenodeoxycholic acid (GDCA) and taurochenodeoxycholic acid (TCDCA), were markedly elevated. NK activity in patients with obstructive jaundice (12.2±2.8%) was lower than normal (43.9±6.7%), but it returned to normal after biliary drainage. Seven-day incubation of lymphocytes from normal volunteers with sera from 6 patients with jaundice resulted invariably in strongly suppressed NK activity in vitro (4.9±5.6%). In a similar experiment, NK activity was entirely unaffected by 7-day incubation with conjugated bilirubin, TCA, TCDCA and GCA, whereas it was significantly inhibited by over 5-day incubation with GCDCA (5-day; 5.6±2.6%, 7-day; 4.3±3.5%, p<0.01). These data clearly indicate that sera from patients with obstructive jaundice suppress NK activity, suggesting that GCDCA is one of the important factors inhibiting NK activity.
