Mannose Receptor Mediates the Immune Response to Ganoderma atrum Polysaccharides in Macrophages

The ability of mannose receptor (MR) to recognize the carbohydrate structures is well-established. Here, we reported that MR was crucial for the immune response to a Ganoderma atrum polysaccharide (PSG-1), as evidenced by elevation of MR in association with increase of phagodytosis and concentrations of interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) in normal macrophages. Elevation of MR triggered by PSG-1 also led to control lipopolysaccharide (LPS)-triggered inflammatory response via the increase of interleukin-10 (IL-10) and inhibition of phagocytosis and IL-1 beta. Anti-MR antibody partly attenuated PSG-1-mediated anti-inflammatory responses, while it could not affect TNF-alpha secretion, suggesting that another receptor was involved in PSG-1-triggered immunomodulatory effects. MR and toll-like receptor (TLR)4 coordinated the influences on the TLR4-mediated signaling cascade by the nuclear factor-kappa B (NF-kappa B) pathway in LPS-stimulated macrophages subjected to PSG-1. Collectively, immune response to PSG-1 required recognition by MR in macrophages. The NF-kappa B pathway served as a central role for the coordination of MR and TLR4 to elicit immune response to PSG-1.