Impact of Hells loss-of-function on DNA methylation in B cells during humoral immune responses: kinetic comparison of Mb1-Hells knockout and control mice by single-cell RNA sequencing

We are interested in deciphering the mechanism by which DNA methylation in late B cell differentiation affects humoral immune response. We chose to study a very rare immunodeficiency called ICF type 4, where a point mutation in a gene encoding the protein HELLS causes a lack of both circulating antibodies and memory B cells in human. HELLS is a chromatin remodeler, that allows for DNA methylation to occur. Using a Hells conditional knock-out in B cells, we measured the kinetics of the immune B cell response, following immunization with NP-CGG, and show a lack of memory and plasma cells accompanied by a defect in germinal center maintenance, but not by its formation. Single cell RNAseq of cell sorted naive, germinal center B cells and memory B cells at day 7 and day 14 post NP-immunization helped us better characterize the phenotype.