Normal human fibroblasts express pattern recognition receptors for fungal (1 -> 3)-beta-D-glucans

Fungal cell wall glucans nonspecifically stimulate various aspects of innat e immunity. Glucans are thought to mediate their effects via interaction wi th membrane receptors on macrophages, neutrophils, and NK cells. There have been no reports of glucan receptors on nonimmune cells. We investigated th e binding of a water-soluble,glucan in primary cultures of normal human der mal fibroblasts (NHDF). Membranes from NHDF exhibited saturable binding wit h an apparent dissociation constant (K-D) of 8.9 +/- 1.9 mug of protein per mi and a maximum binding of 100 +/- 8 resonance units. Competition studies demonstrated the presence of at least two glucan binding sites on NHDF. Gl ucan phosphate competed for all binding sites, with a KD of 5.6 muM (95% co nfidence interval [CI], 3.0 to 11 muM), while laminarin competed for 69% +/ - 6% of binding sites, with a K-D of 3.7 muM (95% CI, 1.9 to 7.3 muM). Gluc an (1 mug/ml) stimulated fibroblast NF-kappaB nuclear binding activity and interleukin 6 (IL-6) gene expression in a time-dependent manner. NF-kappaB was activated at 4, 8, and 12 h, while IL-6 mRNA levels were increased by 4 8% at 8 h. This is the first report of pattern recognition receptors for gl ucan on human fibroblasts and the first demonstration of glucan binding sit es on cells other than leukocytes. It also provides the first evidence that glucans can directly modulate the functional activity of NHDF. These resul ts provide new insights into the mechanisms by which the host recognizes an d responds to fungal (1 -->3)-beta -D glucans and suggests that the respons e to glucans may not be confined to cells of the immune system.