CXCR5 and influenza: The IL-2+ producing T cell bias was not due to overlap of the IL-2+ T cells with T follicular helper (Tfh) cells [15], [38], as the majority of both IFNγ+TNFα+ and IFNγ−IL-2+TNFα+ influenza-specific cells responding to CA/09 and NC/99 were found within the CXCR5− CD4 T cell population (Figure S1).