Redefining the HLA and RA association: To be or not to be anti-CCP positive

An obvious way to unravel the apparently complex association between HLA and RA is to reduce the heterogeneity of this multifactorial disease. Recently, we have discovered that SE positive DRB1 alleles are exclusively associated with CCP positive RA. The previously reported association with RF positive RA appeared to be secondary to the association with anti-CCP pos. RA. This was the case both for the association found for susceptibility and severity. Interestingly, DRB1*03 was exclusively associated with anti-CCP neg. RA. Because recent evidence puts the immune response against citrunilated proteins (CCP) as prime suspect for disease induction and progression in this subgroup of RA these observations are a big leap forwards in solving the HLA-RA puzzle.