TLR4 and tuberculosis: DnaK can activate innate immunity through TLR2 and TLR4 (Bulut et al., 2005; Tsan and Gao, 2009), perhaps explaining its adjuvant properties during vaccination (Suzue and Young, 1996; Bulut et al., 2005), and offering a unique advantage as a TB preventive vaccine when administered via the IN route.