CD4+ follicular regulatory T cells optimize the influenza virus-specific B cell response

CD4+ follicular regulatory T cells (Tfr cells) control B cell responses through the modulation of follicular helper T (Tfh) cells and germinal center development, while suppressing autoreactivity; however, their role in the regulation of productive germinal center B cell responses and humoral memory is incompletely defined. We show that Tfr cells promote antigen-specific germinal center B cell responses upon influenza virus infection. Following viral challenge, we found that Tfr cells are necessary for robust generation of virus-specific, long-lived plasma cells, antibody production against both hemagglutinin (HA) and neuraminidase (NA), the two major influenza virus glycoproteins, and appropriate regulation of the BCR repertoire. To further investigate the functional relevance of Tfr cells during viral challenge, we utilized a sequential immunization model with repeated exposure of antigenically partially conserved strains of influenza viruses, revealing that Tfr cells promote recall antibody responses against the conserved HA stalk region. Thus, Tfr cells promote antigen-specific B cell responses and are essential for the development of long-term humoral memory. Each group consisted of 3-4 mice pooled together Two replicates of each group were used for the HA+_GCB cell RNAseq Three replicates of each group were used for the Tfh cell RNAseq Tfr wildtype and Tfr knockout mice are the two groups studied