Anti-nuclear antibodies (ANA) are frequently detected in patients with psoriasis (Ps) and psoriatic arthritis (PsA), but their target autoantigens remain unknown. We assessed antibody (ab) reactivity against 23 known nuclear antigens in patients with Ps and PsA and assess the effects of secukinumab (anti-IL17A) treatment on ANA levels. A total of 201 patients, 101 with Ps and 100 with PsA, and 50 ANA-negative healthy controls (HCs) were tested for ANAs by a line immunoassay testing reactivity to 23 nuclear antigens. Ab reactivity to at least 1 antigen was found in 20.4% psoriatic disease patients (25.7% Ps and 15% PsA) compared to 8% HCs (p = ns), the most frequent being against dense fine speckled 70 (DFS70) (6.5%). In Ps and PsA patients with secukinumab-induced remission, anti-DFS70 and other antigen-specific autoantibodies were diminished over time. No decline was noted for IgG abs against antigens from pathogens such as cytomegalovirus, Epstein–Barr virus and Helicobacter pylori. Autoantibody decrease was associated with significant reduction of plasmablasts, follicular B and follicular T cells. In conclusion, one third of antigen-specific ANA patients with psoriatic disease recognize DFS70. Secukinumab decreases nuclear antigen autoreactivity, plasmablasts, follicular B and follicular T cells, highlighting a new mechanism of its action.
