Evidence for an CD4 T celldependent, IFNγ independent mechanism of killing has been suggested by thefinding that the frequency of Mtb-specific, IFNγ-producing cells followingimmunization does not correlate with protection against infection and that depletionof CD4 cells exacerbates Mtb infection in mice despite the ongoing expression ofIFNγ [8],[9], [10], [11], [12]. This evidence concerns the gene IFNG and infection.