The β-glucan receptor, dectin-1, is predominantly expressed on the surface of cells of the monocyte/macrophage and neutrophil lineages

We recently identified dectin-1 (βGR) as a major β-glucan receptor on leukocytes and demonstrated that it played a significant role in the non-opsonic recognition of soluble and particulate β-glucans. Using a novel mAb (2A11) raised against βGR, we show here that the receptor is not dendritic cell-restricted as first reported, but is broadly expressed, with highest surface expression on populations of myeloid cells (monocyte/macrophage (MΦ) and neutrophil lineages). Dendritic cells and a subpopulation of T cells also expressed the βGR, but at lower levels. Alveolar MΦ, like inflammatory MΦ, exhibited the highest surface expression of βGR, indicative of a role for this receptor in immune surveillance. In contrast, resident peritoneal MΦ expressed much lower levels of βGR on the cell surface. Characterization of the nonopsonic recognition of zymosan by resident peritoneal MΦ suggested the existence of an additional β-glucan-independent mechanism of zymosan binding that was not observed on elicited or bone marrow-derived MΦ. Although this recognition could be inhibited by mannan, we were able to exclude involvement of the MΦ mannose receptor and complement receptor 3 in this process. These observations imply the existence of an additional mannan-dependent receptor involved in the recognition of zymosan by resident peritoneal MΦ.