In humans, immunization with a live attenuated typhoid vaccine was shown to elicit Salmonella Typhi (S. Typhi)-specific multifunctional CD4+ T cells in the blood that predominantly produced IFN-γ and tumor necrosis factor-α (TNF-α) [34] as well as mucosal immunity at the site of infection driven by CD4+ and CD8+ T cells [35,36]. Here, CD4 is linked to infection.