Numerous reports indicated exacerbation of chronic LCMV infections in the absence of CD4 T cells (Battegay et al., 1994; Altfeld and Rosenberg, 2000; Wiesel and Oxenius, 2012), preventing eventual control of infection (Matloubian et al., 1994; Ou et al., 2001; Fuller and Zajac, 2003; Wherry et al., 2003a). Here, CD4 is linked to infection.