Distinct changes have been observed in the proportions of T follicular helper (Tfh) and CD19+ B cells in the lymph nodes of patients at risk of developing RA (individuals with rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA) but asymptomatic for arthritis) (21), and altered proportions of naïve T cells and T regulatory cells (Treg) have been observed in the peripheral blood (22). Here, PRTN3 is linked to rheumatoid arthritis.