CD4 and infection: In addition to STAT3, IL-6 stimulation also activates STAT1 in CD4+ T cells.111 Antigen-specific CD4+ T cells dually deficient for STAT1 and STAT3 completely fail to form Tfh cells, replicating the outcome of IL-6 deficiency and confirming that STAT1 and STAT3 act in collaboration downstream of IL-6 signaling to promote Tfh ontogeny.80 Of note, during infection, cytokines such as IL-6 are not present in isolation.