Robust effector memory features of human T-bet^hi B cells induced by repeated mRNA vaccination

The heterogeneity of memory B cells in response to repetitive cognate antigen challenges remains to be fully elucidated. Here, we identified a transcriptionally distinct cluster of T-bet^hi B cells, among SARS-CoV-2 RBD-specific B cells in PBMCs from healthy individuals vaccinated with the BNT162b2 SARS-CoV-2 mRNA vaccine. Our findings indicate that T-bet^hi B cells can be defined by a combination of CD11c and FcRL5 receptors, and are distinguished by distinct gene regulatory networks associated with effector functions. Notably, these T-bet^hi B cells were affinity-matured and exhibited rapid differentiation into antibody-secreting cells (ASCs) producing neutralizing antibodies comparable to classical memory B cells, underscoring their role in early recall responses. Taken together, these findings illuminate the potent effector memory roles of T-bet^hi B cells in adaptive immunity following vaccinations.