Overview of the affinity maturation model.

(a) Schematic of AM within a GC. Activated B cells first undergo expansion and somatic hypermutation (SHM), and then they undergo selection based on their ability to bind and internalize antigen presented on FDCs and receive T cell help. A small fraction of positively selected B cells exits as antibody-secreting plasma cells and memory cells. The others undergo another round of mutation and selection. This cycle repeats until a termination condition is met. (b) Schematic of seeding new GCs upon new immunizations. For the first immunization, the seeding cells come solely from naive B cells. For subsequent immunizations, seeding cells come from both the naive and memory cell populations, and newly generated memory cells join the memory cell population. Created with BioRender.com.