In HIV seronegative individuals, the emergence of blood ICOS+CXCR5+CXCR3+ TFH that are able to produce IL-21 correlated with influenza-specific B cell responses (79) and blood ICOS+IL-21+ influenza-specific TFH expand after immunization and correlate to antibody responses (80). The gene discussed is CXCR3; the disease is influenza.