Furthermore, circulating CXCR5+ TFH cells that emerge transiently in human blood following a broad range of viral infection and vaccination, including influenza (74–76), yellow fever (77), HIV-1 (78), and Ebola (79), have a greater capacity for IL-21 and IL-10 production, leading to superior B cell helper responses (80). Here, CXCR5 is linked to viral infectious disease.