Their conclusion was that, in fact, ACPA-negative RA includes two genetically distinctive subsets according to the presence of RF: ACPA-negative/RF-positive RA is associated with HLA-DRB1*04:05 and *09:01, whereas ACPA-negative/RF-negative RA was associated with DR14 and HLA-DR8 homozygote. Here, PRTN3 is linked to rheumatoid arthritis.