Autoimmunity in rheumatoid arthritis has been associated with deficient glycosylation of serum and synovial IgG which could potentially be mediated through the binding of the Fc portion of the molecule to its cognate receptor.
Normal IgG1 and IgG3 were affinity-purified, and sialic acid and galactose were clipped off using neuraminidase and beta-galactosidase, respectively. The binding of these sugar-depleted IgG to the Fc gamma receptors (Fc gamma R)IIIb on polymorphonuclear leukocytes (PMN) was assessed by flow cytometry.
The binding of both asialyl and agactosyl IgG1 and IgG3 to PMN was significantly lower than that of the native IgG1 and IgG3.
These data indicate that agalactosyl and, to a lesser degree, asialyl IgG, do not bind as efficiently as native IgG to Fc gamma R. Such a reduction in the perspective of the heterogeneity of the PMN Fc gamma RIIIb.