Identification of Novel Autoantibodies Associated With Psoriatic Arthritis

Objective The autoimmune etiology in psoriasis remains to be clarified. We therefore undertook this study to identify novel pathogenic autoantigens and autoantibodies in patients with psoriasis, with the aim of shedding light on the molecular and cellular basis of the pathogenesis of psoriasis and psoriatic arthritis (PsA). Methods In this study, we developed an autoantigen array system that harbors a variety of antigens, including typical autoantigens in rheumatic diseases as well as skin antigens, inflammatory mediators, and putative autoantigens in psoriasis. Serum samples from patients with psoriasis (n = 73) were used to interrogate the antigens on the array. In addition, enzyme‐linked immunosorbent assays of individual autoantibodies were used in validation studies. Results Levels of several autoantibodies were found to be elevated in the serum of patients with psoriasis compared to healthy controls; in particular, IgG autoantibodies against 2 novel antigens, LL‐37 and ADAMTS‐L5, were significantly increased in patients with psoriasis. Importantly, serum levels of IgG autoantibodies against LL‐37 and ADAMTS‐L5 were correlated with the Psoriasis Area and Severity Index, and reflected disease progression in longitudinally collected serum samples from patients with psoriasis. Importantly, both anti–ADAMTS‐L5 and anti–LL‐37 autoantibody levels were also significantly elevated in psoriasis patients with PsA compared to those without PsA, suggesting that these molecules may be involved in the pathogenesis of PsA. Conclusion Our findings indicate that these identified autoantibodies may be useful biomarkers and may serve as therapeutic targets in psoriasis and PsA.