Regulated somatic hypermutation enhances antibody affinity maturation
Germinal centers (GCs) are microenvironments where B cells undergo affinity maturation through somatic hypermutation (SHM) and selection by T follicular helper (TFH) cells. While SHM introduces mutations at a fixed rate (~1x10?³ per base pair per division), most mutations are deleterious, particularly in high-affinity B cells undergoing many divisions. This study tests a theoretical model suggesting that high-affinity B cells optimize maturation by dividing more but mutating less per division. Data from mice immunized with SARS-CoV-2 or a model antigen support the model, showing that high-affinity B cells shorten their G0/G1 phases and reduce mutation rates, safeguarding their lineages and improving affinity maturation outcomes. Overall design: Single-cell RNA-seq libraries were prepared using the Chromium Single Cell 5' v2 Reagent Kit (10x Genomics) according to manufacturer's protocol. Libraries were loaded onto an Illumina NextSeq with the mid-Output Kit (150 paired end) for V-D-J analysis or onto an NOVAseq for pooled V-D-J and single  cell gene expression. Hashtag indexing was used to demultiplex the sequencing data and generate gene-barcode matrices, respectively.