TRIM21 and systemic lupus erythematosus: HLA molecules play a key role in autoantibody production as demonstrated by one Japanese study that identified both SLE risk signature and autoantibodies to ribonucleoprotein (RNP), SSA/Ro60, SSB/La, cardiolipin were localized to the peptide binding groove of HLA-DRB1 and anti-Sm to HLA-DPB1 (52).