Receptor (or element of a larger receptor complex) for C1q, mannose-binding lectin (MBL2) and pulmonary surfactant protein A (SPA). May mediate the enhancement of phagocytosis in monocytes and macrophages upon interaction with soluble defense collagens. May play a role in intercellular adhesion. Interacts with C1QBP; the association may represent a cell surface C1q receptor. Widely expressed. Highly expressed in lung and heart. Expressed at lower level in brain, thymus, liver, spleen, intestine, kidney, adrenal gland, muscle and testis. Expressed on endothelial cells, platelets, undifferentiated monocytes and circulating natural killer cells. N- and O-glycosylated.