Complement Receptor 1: disease associations and therapeutic implications

Abstract

Exaggerated complement activation is a key event in the pathogenesis of a range of autoimmune and inflammatory diseases. Complement Receptor 1 (CR1) has emerged as a molecule of immense interest in gaining insight to the susceptibility, pathophysiology, diagnosis, prognosis and therapy of such diseases. This review brings forth a composite view of the current understanding on the structure, functions, genetics, disease associations and therapeutic implications of CR1.

Fig. 1

Schematic representation of the F allele (CR1-A) of CR1: from the NH₂ terminus–Site X binds C4b, Sites Y show binding to C3b, C4b PfEMP1, Site Z (SCR 25) is the site for Swain–Langley (Sl) and McCoy (McC) Knops blood group polymorphism. LHR-D also has sites specific for MBL (Mannan-binding lectin) and C1q. TM: transmembrane region; CP: cytoplasmic Tail.

Fig. 2

Regulation of the complement cascade and immune complex clearance by CR1(A) erythrocyte CR1 involved in complement pathway regulation and immune complex clearance (B) polymorphonuclear (PMN) Cell CR1 and monocyte CR1 involved in phagocytosis (C) B-cell CR1 involved in B-cell regulation.

Fig. 3

Down regulation of LCR1 and its possible role in the pathophysiology of SLE. Also shown is the unexplained link between CR1 up-regulation and state of disease remission (adapted from the Ph.D. Thesis, Vaishali Arora, 2007).

Fig. 4

Sustenance of HIV Infection and further spread–During anti-retroviral therapy virus survives in association with ECR1 and also spreads to B cells via CR2 (Complement Receptor 2) after Factor I mediated breakage of HIV associated C3b to iC3b.

Fig. 5

CR1–Fv anti-Rh(D) complex-mediated increase in ECR1 levels in individuals with ECR1 deficiency.

Fig. 6

Specific inhibition of autoreactive B-Cells (here dsDNA) by chimeric CR1-DNA mimotope.