PTK2 and rheumatoid arthritis: Lastly, when comparing serum autoantibody profiles directly between the two RA subgroups, we found 3 autoantibodies having higher abundances in ACPA+ RA compared with ACPA− RA (i.e., anti-HOMER2, anti-PTK2, anti-TPM4); and 3 autoantibodies lower in ACPA+ RA compared with ACPA− RA (i.e., anti-TGIF2, anti-KAT7, anti-BATF) (Supplementary Table 7).