The DERAA (D = aspartic acid, E = glutamic acid, R = arginine, A = alanine) sequence of amino acids at Position 70–74 in the HVR3 of the DRβ1 chain is considered the most important protective factor for seropositive RA, however, the mechanism of this allele-based protection is unknown [62]. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.