Soluble FcγRIIa inhibits rheumatoid factor binding to immune complexes

Abstract

Soluble low-affinity receptors for IgG are known to inhibit immune complex (IC)-mediated inflammation, and expression by leukocytes is elevated in several inflammatory diseases. Immunoglobulin M (IgM) rheumatoid factors (RF), anti-Fc autoantibodies, are found in autoimmune diseases, such as rheumatoid arthritis (RA), as well as in normal immune responses. This study demonstrated that soluble FcγRIIa inhibits the interaction of rheumatoid factors with ICs. The recombinant soluble low-affinity FcγR, rsFcγRIIa, partially inhibited (30-70%) the rate of precipitation of soluble ICs by RF-positive RA sera. This required the normal interaction of FcγRIIa with Fc as the effect could be abrogated wit..