CXCR5 and infection: Deleting p19Arf alone did not exhibit detectably impact on TFH cells elicited by the LCMV-Arm infection, and ablating p19Arf in Ezh2–/– cells rectified the frequency of CXCR5+SLAMlo TFH cells and partially restored TFH cell numbers on 4 dpi (Fig. 5e).