Germinal centers are free for all

Germinal centers (GCs)—the sites of antibody development—are not exclusive niches for rookie B cells. They are also open to experienced old-timers, according to Bende et al. (page 2655).

GCs are temporary lymph node structures that form during an immune response to help newly activated B cells better recognize an antigen. As they proliferate, the B cells' antibody-encoding DNA is mutated. The environment of the GC somehow helps select the best new clones, which then differentiate into either memory B cells or cells that secrete high-affinity antibodies.

This transition route from low to high affinity within GCs was thought to be used exclusively by B cells that encounter antigen for the first time. But Bende and colleagues now find that...