Bos et al. [35] reported that both anticitrullinated protein antibody- (ACPA-) IgG1 and IgG4 of RA patients reduced significantly after 46-week infliximab or 28-week adalimumab treatment, accompanied by significant reduction of ACPA-IgG4/IgG1 ratio, indicating preferential decrease in ACPA-IgG4. This evidence concerns the gene PRTN3 and rheumatoid arthritis.