Complement Receptors

Abstract

Complement receptors are membrane proteins, expressed on cells involved in the immune response, which bind a wide range of the protein fragments generated in the course of complement activation. Through these cellular interactions, the complement system plays a crucial role combating infection. Thus, complement is instrumental in the recruitment of blood leucocytes to a site of inflammation, in promoting phagocytosis and/or extracellular killing of the microorganisms by these cells and in clearance of particulate and soluble immune complexes (ICs) generated at the infected site or released in the circulation. Furthermore, complement is intimately involved in the development of an acquired immune response towards invading pathogens both through the induction of primary B‐cell responses and through shaping of T‐cell responses towards the antigen. This article presents a systematic account of the complement receptors in terms of their structure, cellular distribution and biological and signalling functions. 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.

Effects of Complement Opsonization of HIV on Dendritic Cells: and Implications for the Immune Response

“…CR3 and CR4 bind iC3b selectively, and neither of these receptors bind C3b [123]. C3b can be recognized by CR1 (CD35), but this receptor is not expressed on dendritic cells [124]. CR1 is expressed on monocytes, macrophages, neutrophils, eosinophils, basophils, natural NK cells, B cells and some T cells, as well as follicular dendritic cells, glomerular podocytes, Kupffer cells and erythrocytes [124].…”

Characterization of secreted aspartyl proteases in Candida parapsilosis

“…Based on their binding specificity to the complement proteins, these receptors can be classified in three broad categories. (i) receptors binding to the anaphylatoxins C3a, C5a, and C5a desArg (C3aR, C5aR), (ii) receptors binding to C3 fragment, C3b and its degradation products, iC3b and C3dg (CR1, CR2, CR3, CR4) and (iii) receptors for C1q and related collagenous lectins (cC1qR, C1qRp, gC1qR)121 . These receptors play important roles in complementmediated phagocytosis, NO synthesis, leucocyte chemo-attraction, degranulation, and B-cell proliferation122 .…”