Imaging of Germinal Center Selection Events During Affinity Maturation

TLDR

The germinal center is key for generating high‑affinity B cells, yet its cell migration and interaction dynamics have not been directly observed. We propose a model that competition for T cell help dominates GC B cell selection. GC B cells are highly motile, extend long processes, move between dark and light zones, divide in both, spend only hours in the light zone, form few stable contacts with T cells, and are frequently engulfed by T cells.

Abstract

The germinal center (GC) is an important site for the generation and selection of B cells bearing high-affinity antibodies, yet GC cell migration and interaction dynamics have not been directly observed. Using two-photon microscopy of mouse lymph nodes, we revealed that GC B cells are highly motile and extend long cell processes. They transited between GC dark and light zones and divided in both regions, although these B cells resided for only several hours in the light zone where antigen is displayed. GC B cells formed few stable contacts with GC T cells despite frequent encounters, and T cells were seen to carry dead B cell blebs. On the basis of these observations, we propose a model in which competition for T cell help plays a more dominant role in the selection of GC B cells than previously appreciated.