CD4 and infection: Immune responses against Lm commence with an early innate phase including macrophages, inflammatory monocytes, NK-cells, DCs, CD4+, CD8+ and γδT cells that together constrain the infection (Andersson et al., 1998; Lee et al., 2013; Pamer, 2004b; Shi et al., 2011; Unanue, 1997).