Fc gamma receptor III (Fc gamma RIII) is one of the 3 structurally distinct families of receptors for the Fc domain of IgG, and its Fc gamma RIIIb isoform is exclusively expressed in polymorphonuclear (PMN) cells. We sought to detect anti-Fc gamma RIII autoantibodies in serum from patients with primary Sjögren's syndrome (SS).
Sixty-six patients with SS and 44 healthy controls were enrolled in the study. ELISA were developed.
IgG and IgM autoantibodies were found in 16 (10 IgG+ IgM+ and 6 IgG+ IgM-) and 24 patients (10 IgG+ IgM+ and 14 IgG- IgM+) respectively. Their frequency was higher in patients with nonerosive arthritis (p < 0.02), Raynaud's phenomenon (p < 0.003), and lung involvement (p < 0.02) than in patients without such complications. The levels of IgM and IgG antibody (p < 0.05) correlated with the content of IgA without the circulating immune complex (IC), while there was no relationship between anti-Fc gamma RIII activity and the PMN count.
Anti-Fc gamma RIII autoantibodies may act as an acquired additional factor further compromising IC handling in individuals who share HLA-DR3 alloantigen.