Complement Receptors

Abstract

Abstract Complement receptors are membrane proteins, expressed either on or in the cells that drive or regulate immune responses. They bind a wide range of the protein fragments generated in the course of canonical and non‐canonical complement activation. Interaction of such fragments with their cognate receptors activates and regulates the function of immune and stromal cells. Through these pathways, complement receptors control the recruitment of blood leucocytes to the sites of inflammation, promote phagocytosis and/or extra‐cellular killing of microorganisms by immune cells and clearance of particulate and soluble immune complexes generated during infectious or non‐infectious inflammatory events. Furthermore, complement receptor activation drives and controls the development of adaptive immune responses towards pathogens, allergens, auto‐antigens and altered self‐molecules through the induction of primary B and T lymphocyte responses. This article provides basic insights into the structure, cellular distribution as well as biological and signalling functions of the different complement receptors. Key Concepts Structural diversity of receptors reflecting the diversity of the complement fragments engaged. Functional diversity, depending on the type of complement fragment involved and/or the type of cells expressing the appropriate receptor. Intra‐cellular expression and function of anaphylatoxin receptors. Homo‐ and heterodimerisation of anaphylatoxin receptors that alter their biologic functions. Cross‐talk of complement receptors with several other receptor classes.