TRAF1 and rheumatoid arthritis: QTLs identified on six chromosomes matched two human RA risk alleles (TRAF1/C5 and PADI4 loci), of which the Traf1/Hc locus on mouse chromosome 2 (mChr2) is a dominant QTL in both CIA (mCia2 and mCia4) and PGIA (Pgia2) (Table 1).