Research Highlight An Expanding Job Description for Bcl6

B cell lymphoma/leukemia gene 6 (Bcl6) is well known as a master regulator of germinal center (GC) B cell differentiation. Now, three new publications demonstrate that Bcl6 also plays a second role in GC response, in that it is both required and sufficient to drive the differentiation of T follicular helper cells. Germinal centers (GCs) are dynamic struc-tures within secondary lymphoid tissues that are responsible for the generation of B cell memory and high-affinity antibodies (Manser, 2004). During a T cell-dependent antibody response, GCs form after naı̈ve B cells are activated by cognate T cells, migrate to the boundary between the B and the T cell areas and initiate rapid focal expansion within a follicular dendritic cell network. Proliferating GC B cells diver-sify their immunoglobulin genes throug