Little has been reported about the effects of different polysaccharides on cytokine production from human monocytes. In this study, we show that several well-defined polysaccharides, including polymers with different sizes of beta 1-4-linked D-mannuronic acid (poly-M, high-M alginate, and M-blocks) and cellulose oxidized in the C-6 position, induced human monocytes to produce tumor necrosis factor alpha (TNF-alpha). Poly-M was the most efficient polysaccharide tested and, on a weight basis, was approximately as efficient as lipopolysaccharide (LPS) from Escherichia coli. TNF-alpha production was shown to depend strongly on the molecular weights of poly-M and high-M alginate, with maximal TNF-alpha production occurring at molecular weights above 50,000 and 200,000, respectively. G-blocks, alpha 1-4-linked L-guluronic acid polymers that did not induce cytokine production from monocytes, reduced the cytokine production induced by the beta 1-4-linked polyuronic acids and LPS. Furthermore, both G-blocks and LPS were found to inhibit the binding of poly-M to monocytes, as measured by flow cytometry. In addition, we found that the binding of LPS to monocytes was inhibited by G-blocks, M-blocks, and poly-M. Our results indicate that beta 1-4-linked polyuronic acids and LPS may stimulate monocytes to produce TNF-alpha by similar mechanisms and may bind to a common receptor
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