As there is ample evidence of PG-specific immune responses in mice with PGIA or GIA [18][20][22] and some evidence of Cit PG-specific immunity in RA patients [23–25], we also sought to uncover similarities in the immune recognition pattern of PG epitopes between mice with PGIA and ACPA+ RA patients, between mice with GIA and ACPA- RA patients, as well as between naïve mice and healthy control human subjects. This evidence concerns the gene PRTN3 and rheumatoid arthritis.