ATL2 and granulomatosis with polyangiitis: In GPA patients, the IgG responses per antigen appeared overall lower than in HC, and this reached statistical significance for several surface proteins (ClfA, ClfB, FnbpA, and SdrE) and secreted proteins (Atl-2, CHIPS, Efb, Lipase, NUC, SCIN, SEN, SEO, SSL3 and TSST-1).