HLA-DRB5 and rheumatoid arthritis: Cluster 0 harboured the hyper expanded clone from Pt2-SP and top markers included HLA genes (HLA-DRB5, HLA-DRB1, HLA-DQA1, HLA-DRA) and chemokine CXCR6 known to have a role in B cell migration in RA (Zhao 2022) (Fig. 2h).