T-bet high atypical memory B cells exhibit effector memory features in mRNA vaccine recipients 2256789

Abstract

Abstract Introduction T-bet high B cells, also referred to as atypical or double-negative 2 (DN2) B cells, are defined by high expression of the transcription factor T-bet (TBX21) and typically expand during chronic infections and autoimmune conditions. In severe viral infections such as COVID-19, these cells arise through extrafollicular activation and have been implicated in both protective neutralizing antibody responses and immunopathology. However, their molecular and functional properties in the context of repeated vaccination remain poorly understood. Methods In this study, we examined SARS-CoV-2 receptor-binding domain (RBD)-specific memory B cells from individuals who received multiple doses of the BNT162b2 mRNA vaccine. By integrating multi-omics single-cell sequencing, gene regulatory network analyses, immunophenotyping, and functional assays, we characterized the effector memory features of T-bet high memory B cells. Results Our results show that T-bet high memory B cells can be identified by co-expression of CD11c and FcRL5 and are governed by distinct gene regulatory networks linked to effector functions. These cells were affinity-matured and rapidly differentiated into antibody-secreting cells (ASCs) that produced neutralizing antibodies at levels comparable to classical memory B cells, highlighting their contribution to early recall responses. Subclustering further revealed heterogeneous subsets, including one enriched for RBD-specific cells and expressing markers indicative of recent antigen exposure. Conclusion Taken together, our findings provide a comprehensive view of the transcriptional and functional diversity of human B cells and delineate the trajectory of T-bet high B cells from initial activation through repeated antigenic stimulation. The strong effector memory characteristics of these cells underscore their potential as immunological markers and promising targets for optimizing future vaccine strategies. Funding Source n/a Topic Categories Immune Mechanisms of Human Disease (HUM)