Determining germinal centre B cell fate.

The humoral immune system generates immunological memory comprising affinity matured, long-lived memory B cells and plasma cells (PCs), which are generated primarily in germinal centres (GCs). Although many factors are essential in this process, those that specifically govern B cell fate are not fully understood. The provision of T cell help to B cells is key in GC B cell fate determination, and it has become clear recently that this help involves more than direct cell-cell interactions. Recently, the cytokine interleukin (IL)-21 has been identified as a key factor that can modulate the processes within GCs and directly influence B cell fate. In this review, we examine the roles of GC cytokines in the context of cell differentiation.