Proposed biology of PBL. The GC reaction occurs in the primary follicle. Naïve B cells gain exposure to antigen, and B-cell clones undergo selection by alternating between the dark and light zones of the GC (upper panel). EBV infection could play a role in preventing apoptosis via several mechanisms such as induction of NF-κB, through Syk/Src mediation, and induction of BAX/BAK (left lower panel). Conversely, MYC translocations could allow B cells to escape the inhibitory influence of BLIMP-1 favoring plasmablast development but then inhibiting further plasmacytic differentiation by downregulating PAX5 (right lower panel). T_H, T helper cell.