Serum levels of anti-Fcγ receptor IIB/C antibodies are increased in patients with systemic sclerosis.

Abstract

Systemic sclerosis (SSc) is a systemic autoimmune disorder that results in fibrosis of the skin and multiple internal organs. Although the precise mechanism is unknown, it appears to result from the overproduction of extracellular matrix proteins and aberrant immune activations. Receptors for the Fc region of immunoglobulin (Ig)G (FcγR) are members of the Ig superfamily that modulate both activation and inhibition of immune responses. FcγRIIB is the sole inhibitory member, which has an intrinsic cytoplasmic immunoreceptor tyrosine-based inhibitory motif. The present study was undertaken to investigate the circulating concentrations of anti-FcγRIIB/C antibodies (Ab) in patients with SSc. Serum levels of anti-FcγRIIB/C Ab were significantly increased in patients with SSc compared to those in controls and in patients with localized scleroderma. Serum levels of anti-FcγRIIB/C Ab in patients with limited cutaneous SSc were similar to those in patients with diffuse cutaneous SSc. Among SSc patients, serum levels of anti-FcγRIIB/C Ab were increased in those with nail-fold bleeding and decreased in those with diffuse pigmentation and calcinosis. These findings support the notion that increased serum anti-FcγRIIB/C Ab levels are involved in aberrant immune responses in SSc.