Potential of the dual IFN-γ/IL-2 fluorescence-immunospot assay to distinguish different stages in bovine tuberculosis.

•A dual colour IFN-γ/IL-2 FluoroSpot assay has been developed for enumeration of bovine T cell responses.•Dual IL-2+IFN-γ+ T cells were identified as the largest PPD-B responsive T cell subset.•The frequency of cytokine producing cells and the proportion of IL-2 single producers were significantly higher in animals with visible lesions.•The greater levels of single IL-2 producing T cells associated with the presence of pathology could be a potential biomarker for active TB in cattle.