| Abstract |
The effect of serum on LPS-induced activation of a murine macrophage-like cell line, WEHI-3, was examined. Foetal calf serum strongly inhibited the production 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 lines, J774.1 and BAM3, on treatment with LPS. This suppressive effect of serum on WEHI-3 cells was most remarkable when the cells were stimulated with rough-chemotype LPS, Ra LPS, Rc LPS and Rd2 LPS. Foetal calf serum also inhibited TNF-alpha production by the same cells stimulated with high concentrations of smooth-form LPS (S LPS; > 1000 ng/mL). Serum-mediated suppression was also observed for expression of the TNF-alpha gene in Rc LPS-stimulated 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 of FCS addition to LPS-stimulated cells. No significant difference was observed 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-mediated 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 with low concentrations (< 100 ng/mL) of S LPS and rough mutant Salmonella minnesota Re LPS. These results suggest that the ability of FCS to suppress LPS-induced activation of WEHI-3 cells in mainly dependent on the structure of polysaccharide chains and also on the concentration of LPS employed.
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