Anti-agalactosyl IgG antibody in ankylosing spondylitis and psoriatic arthritis

Anti-agalactosyl IgG antibody (anti-Gal(0) IgG) has been regarded as a useful serological marker for rheumatoid arthritis (RA). It is unknown whether it is also elevated in serum and implicated in the pathogenesis of joint inflammation in seronegative spondyloarthropathy (SpA) such as ankylosing spondylitis (AS) and psoriatic arthritis (PsA). Sera were collected from 43 patients with AS or PsA with axial joint involvement, 22 patients with RA, and 25 healthy normal individuals for the detection of anti-Gal(0) IgG with a cup-type lectin enzyme immunoassay (Eitest CA^.RF). The disease activity of the AS/PsA was evaluated by Bath Ankylosing Spondylitis Disease Activity Score (BASDAI), the serum C-reactive protein (CRP) and IgA were measured by nephelometry, and erythrocyte sedimentation rate (ESR) was measured by Westergren’s method. The median titers of anti-Gal(0) IgG were significantly elevated in patients with RA (167.85, 15.73∼797.58 AU/mL) and AS/PsA (186.15, 34.71∼651.19 AU/mL), compared to those of the normal controls (13.04, 12.00∼202.43 AU/mL). The titers of the anti-Gal(0) IgG in patients with AS/PsA were correlated to the BASDAI scores (r ² = 0.422, SEE = 1.443, p < 0.001) and serum CRP (r ² = 0.345, SEE = 2.434, p < 0.001) but not to IgA (r ² = 0.0259, SEE = 126.30, p < 0.001) or ESR (r ² = 0.171, SEE = 31.053, p = 0.0059). Collectively, the anti-Gal(0) IgG is elevated and vaguely correlated with the disease activity of AS/PsA although its titers in these patients were erratic. The result of the present investigation has suggested that anti-Gal(0) IgG may be more ubiquitously present in inflammatory arthritides including RA or SpA.