PMID: 9427722Jan 15, 1998Paper

A naturally occurring mutation in Fc gamma RIIA: a Q to K127 change confers unique IgG binding properties to the R131 allelic form of the receptor.

Blood
C F NorrisS E McKenzie

Abstract

Fc gamma RIIa is widely expressed on hematopoietic cells. There are two known allelic polymorphic forms of Fc gamma RIIa, Fc gamma RIIa-R131 and Fc gamma RIIa-H131, which differ in the amino acid at position 131 in the second lg-like domain. In contrast to Fc gamma RIIa-R131, Fc gamma RIIa-H131 binds hlgG2 but not mIgG1, and this differential binding has clinical implications for host defense, autoimmune disease, immunohematologic disease, and response to therapeutic monoclonal antibodies. We identified a novel Fc gamma RIIA genotype in a healthy individual homozygous for Fc gamma RIIA R/R131 in whom a C to A substitution at codon 127 changes glutamine (Q) to lysine (K) in one of the two Fc gamma RIIA genes. This individual's homozygosity for Fc gamma RIIA-R/R131 leads to the prediction that the receptors on her cells would not bind hIgG2. Monocyte and neutrophil phagocytosis of hIgG2-opsonized erythrocytes was significantly higher (P < .05) for cells from this K/Q127, R/R131 individual than for Q/Q127, R/R131 donors. Platelet aggregation stimulated by an mIgG1 anti-CD9 antibody in this individual was significantly different (P < .05) from Q/Q127, H/R131 and Q/Q127, H/H131 donors and similar to Q/Q127, R/R131. Our data show tha...Continue Reading

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