Integrating this data in our analysis, we found that the cluster of CD4 + TRB clones that harbors the QDFA amino acid motif is both enriched in the RA repertoire and associated with HLA-DRB1*15, the class II HLA variant that is most strongly associated with RA risk in the Spanish population. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.