Suppressive effects of serum on the LPS-induced production of nitric oxideand TNF-a by a macrophage-like cell line, WEHI-3, are dependent on the structure of polysaccharide chains in LPS

The effect of serum on LPS-induced activation of a murine macrophage-like c ell line, WEHI-3, was examined. Foetal calf serum strongly inhibited the pr oduction of nitric oxide (NO) and TNF-alpha by LPS-stimulated WEHI-3 cells, while it enhanced the production of both by other macrophage-like cell lin es, J774.1 and BAM3, on treatment with LPS. This suppressive effect of seru m on WEHI-3 cells was most remarkable when the cells were stimulated with r ough-chemotype LPS, Ra LPS, Re LPS and Rd(2) LPS. Foetal calf serum also in hibited TNF-alpha production by the same cells stimulated with high concent rations of smooth-form LPS (S LPS; > 1000 ng/mL). Serum-mediated suppressio n was also observed for expression of the TNF-alpha gene in Re LPS-stimulat ed WEHI-3 cells. This suppressive effect of FCS was most remarkable during the 1-2 h before the addition of LPS, but it was not observed when FCS was added at 1 h after the addition of LPS, suggesting dependence on the time o f FCS addition to LPS-stimulated cells. No significant difference was obser ved in the expression of CD14 on WEHI-3 cells cultured in the presence and absence of serum, suggesting that CD14 is not involved in the serum-mediate d suppression of these LPS-responses. On the contrary, FCS showed enhancing effects on the production of NO and TNF-alpha by WEHI-3 cells stimulated w ith low concentrations (< 100 ng/mL) of S LPS and rough mutant Salmonella m innesota Re LPS. These results suggest that the ability of FCS to suppress LPS-induced activation of WEHI-3 cells is mainly dependent on the structure of polysaccharide chains and also on the concentration of LPS employed.