Once bacteria start to replicate intracellularly, innate immunity remains important, for example, through Nramp-1, as well as the linked activation of adaptive immunity.7 Interferon-γ (IFN-γ) is probably derived largely from natural killer cell activation initially, and subsequently from T helper type 1 (Th1) cells,10 and the importance of this pathway in defence is shown by the preponderance of Salmonella infections among individuals with interleukin-12/IFN-γ defects.11 During the final phase, bacterial levels in tissues fall until clearance is achieved. This evidence concerns the gene IFNG and Salmonella Infections.