To evaluate expression of the PTPN22 splice forms, we measured the expression levels of PTPN22-long isoforms and the short isoform PTPN22_v4 (LYP2; Figure 1), relative to ZNF592 expression in PBMCs of healthy individuals and RA patients (cohort I) after 6 h of cultivation of cells without stimulation. Here, ZNF592 is linked to rheumatoid arthritis.