CXCR5/CXCL13 pathway, a key driver for migration of regulatory B10 cells, is defective in patients with rheumatoid arthritis

Objectives Chemokines (CKs) are key players of immune-cell homing and differentiation. CK receptors (CKRs) can be used to define T-cell functional subsets. We aimed to characterize the CKR profile of the regulatory B-cell subset B10+ cells and investigate the CKs involved in their migration and differentiation in healthy donors and patients with RA. Methods RNA sequencing and cytometry were used to compare CKR expression between B10+ and B10neg cells. Migration of B10+ and B10neg cells and IL-10 secretion of B cells in response to recombinant CKs or synovial fluid (SF) were assessed. Results CXCR5 was expressed at a higher level on the B10+ cell surface as compared with other B cells (referred to as B10neg cells). In line with this, its ligand CXCL13 preferentially attracted B10+ cells over B10neg cells. Interestingly, synovial fluid from RA patients contained high levels of CXCL13 and induced strong and preferential migration of B10+ cells. Besides its role in attracting B10+ cells, CXCL13 also promoted IL-10 secretion by B cells. In RA patients, the level of CXCR5 on B-cell surface was reduced. The preferential migration of RA B10+ cells toward CXCL13-rich SF was lost and CXCL13 stimulation triggered less IL-10 secretion than in healthy donors. Conclusion Our results identify that the CXCR5/CXCL13 axis is essential for B10+ cell biology but is defective in RA. Restoring the preferential migration of B10+ within the affected joints to better control inflammation may be part of the therapeutic approach for RA.