Model for the development of haemophagocytosis in S. enterica-infected mice. A.S. enterica (green) resides within macrophage vacuoles. B. The bacteria kill the macrophage via pyroptosis, releasing the inflammatory cytokines IL-18 and IL-1β. Early in infection, IL-18 and IL-1β stimulate NK and NKT cells to produce IFNγ. After the onset of adaptive immunity, T-cells (CD4 and CD8) also produce IFNγ. C. Positive feedback loops, including IL-12 stimulation of NK, NKT and T-cells, help maintain IFNγ production. D. IFNγ stimulates macrophages to phagocytose non-adherent cells. E. Haemophagocytic macrophages may provide S. enterica with a survival niche. It is unknown whether S. enterica reside within vacuoles in haemophagocytic macrophages, as drawn.