The BOVIGAM® 2G kit is a blood-based assay of cell-mediated immunity that has been validated together with tuberculin PPDs and a panel of stimulation antigens. The combined use of these different stimulation antigens with tuberculin PPDs allows adjustment of the application of the test to specific TB situations. It is based on the detection of cell-mediated immune response to infection with Mycobacterium bovis in cattle, sheep, goats, buffalo, bison, and other bovidae. The BOVIGAM® 2G test involves two stages. In the first stage, blood samples are incubated overnight with antigens, such as tuberculin purified protein derivative (PPD) or the newly developed 'peptide cocktails', to stimulate lymphocytes to produce IFN-γ. In the second stage, IFN-γ in the plasma supernatants of each blood aliquot is determined using a sandwich ELISA. IFN-γ present in the sample binds to anti-bovine IFN-γ monoclonal antibodies on a solid support and is visualized with a second anti-IFN-γ antibody labeled with an enzyme that generates a color signal. Color development is proportional to the amount of bound IFN-γ.