IFNG and tuberculosis: However, the current study has emphasised the benefit of using the combination of the PPD and ESAT-6/CFP10 IFN-γ tests for bovine TB diagnosis as some positive ESAT-6/CFP10 IFN-γ responses in non-infected animals can arise from exposure to some environmental mycobacteria [38] or to activation of NK cells in young animals [39].