This is probably due to the HMBPP from B. pseudomallei further stimulating the γ9+ T cells in vivo. In addition to the effects on γ9+ T cell IFN-γ expression, an apparent ‘bystander’ effect on γ9− T cells IFN-γ expression was observed during infection suggesting that the general T cell response was skewed towards an IFN-γ effector response appropriate for intracellular pathogen killing. Here, IFNG is linked to infection.