CD4 and infection: By secreting IFNγ in the first days of infection (Belnoue et al, 2002; Villegas‐Mendez et al, 2012), CD4 T cells promote CXCL9‐ and CXCL10‐dependent CXCR3‐mediated accumulation of CD8 T cells in the brain (Campanella et al, 2008; Van den Steen et al, 2008).