TRAF1 and rheumatoid arthritis: The present study supports an association between HLA-DRB1 SE alleles, PTPN22, OLIG3/TNFAIP3, STAT4 and TRAF1/C5 with susceptibility to autoantibody-positive RA, but only the TRAF1/C5 locus was associated with disease severity in this cohort, although this would no longer remain significant after correction for multiple comparisons.