The aim of this study was to evaluate the effect of lipopolysaccharide (LPS) administration, which mimics a surgical intervention, on the immune status of obstructive jaundiced (OJ) and sham-operated control rats. Rats were given 20 mug LPS intraperitoneally on day 13 following bile duct ligation or sham surgery. We determined serum levels of tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) on day 14 after surgery, and spontaneous as well as LPS-induced production of these cytokines in splenocyte and peritoneal exudate cell cultures (PEC). We found that IL-6, but not TNF-alpha, serum concentrations were significantly elevated (4-fold) in OJ rats treated with LPS compared with LPS-untreated OJ rats. In sham-operated rats the differences between the respective groups were not significant. The production of TNF-alpha by splenocyte and PEC cultures was depressed in OJ rats treated with LPS; in particular, a very deep decline was observed in the case of spontaneous TNF-alpha production in PEC cultures. In contrast, TNF-alpha production in LPS-untreated and LPS-treated sham-operated rats did not differ. In the case of IL-6 production by splenocytes and PEC cultures, we observed a significant suppression of this cellular function in both OJ and sham-operated rats treated with LPS when compared with the respective controls. In conclusion, the results indicate that the already depressed cytokine production in OJ rats leads to even deeper hyporeactivity following LPS challenge. Lack of TNF- alpha suppression upon LPS treatment in sham-operated rats suggests that surgery-elicited hyporeactivity is mediated by a different mechanism than that leading to immune hyporesponsiveness in OJ. Our findings may explain the relatively high mortality rates of OJ patients subjected to surgery.