PTPN22 and rheumatoid arthritis: The difference in expression was significant for the ratio of the transcripts (P = 0.02 and P = 0.01 for cohorts II and III, respectively) and demonstrated a similar trend for higher expression of PTPN22-long isoforms in cohort II and lower expression of PTPN22_v4 in cohort III (P = 1.2 × 10-4) for patients with RA (Table 1).