Publisher Summary Germinal center (GCs) represents a remarkable lymphoid
microenvironment that functions to expand and diversify antigen-reactive lymphocyte clones.
Although the GC reaction is antigen dependent, GCs share many of the processes usually
thought to occur during primary lymphopoiesis, including positive and negative selection,
elimination of self-reactive cells, and enrichment of the repertoire of antigen receptors. The
mechanisms that underlie these processes remain unknown, but it is clear that these issues …