Complement Receptors in Myeloid Cell Adhesion and Phagocytosis

Myeloid cells make extensive use of the complement system in the context of recruitment, phagocytosis, and other effector functions. There are several types of complement receptors on myeloid cells, including G protein-coupled receptors for localizing the source of complement activation, and three sets of type I transmembrane proteins that link complement to phagocytosis: complement receptor 1, having an extracellular domain with tandem complement regulatory repeats; complement receptors 3 and 4, which are integrin family receptors comprising heterodimers of type I transmembrane subunits; and VSIG4, a member of the Ig superfamily. This review will focus on the role of the different classes of complement receptors and how their activities are integrated in the setting of immune tolerance and inflammatory responses.