Phenotypic, transcriptomic, and spatial characterization of CD45RB naïve mature B cells: Implications in Sjögren's disease.

The conventional classification of mature B cells overlooks the diversity within IgD CD27 naïve B cells. Here, to identify distinct mature naïve B cells, we categorized CD45RB B cells (NA RB-) and CD45RB B cells (NA RB+) and explore their function and localization in circulation and tissues under physiological and pathological conditions. NA RB+ B cells, found in secondary lymphoid organs, differentiate into plasmablasts and secrete IgM. In Sjögren's disease, their numbers decrease, and they show over-activation and abnormal migration, suggesting an adaptive disease response. NA RB+ B cells also appear in inflamed salivary glands, indicating involvement in local immune responses. These findings highlight the distinct roles of NA RB+ B cells in health and Sjögren's disease.