C-reactive protein (CRP) is involved in host defense, regulation of inflammation, and modulation of autoimmune disease. Although the presence of receptors for CRP on phagocytes has been inferred for years, their identity was determined only recently. FcγRIa, the high-affinity IgG receptor, binds CRP with low affinity, whereas FcγRIIa, the low-affinity IgG receptor, binds CRP with high affinity. Because the single nucleotide polymorphism in FcγRIIA — which encodes histidine or arginine at position 131 — strongly influences IgG2 binding, we determined this polymorphism’s effect on CRP binding. CRP bound with high avidity to monocytes and neutrophils from FcγRIIA R-131 homozygotes, and binding was inhibited by the R-specific mAb 41H16. CRP showed decreased binding to cells from FcγRIIA H-131 homozygotes (which bind IgG2 with high affinity). However, IFN-γ enhanced FcγRI expression by H-131 monocytes and increased CRP binding. FcγRIIa heterozygotes showed intermediate binding. CRP initiated increases in [Ca2+]i in PMN from R-131, but not from H-131 homozygotes. These data provide direct genetic evidence for FcγRIIa as the functional, high-affinity CRP receptor on leukocytes while emphasizing the reciprocal relationship between IgG and CRP binding avidities. This counterbalance may affect the contribution of FcγRIIA alleles to host defense and autoimmunity.
Mary-Pat Stein, Jeffrey C. Edberg, Robert P. Kimberly, Erin K. Mangan, Dwaipayan Bharadwaj, Carolyn Mold, Terry W. Du Clos
Usage data is cumulative from October 2018 through October 2019.
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.