Dual-colour LysiSpot assay. Dual-colour LysiSpot assay results from three different experiments (mean ± SD), expressed as net number of spots per well (spots from control wells containing only target cells or PBMC cultured alone were subtracted from the spots counted in the cocultures. DHD-K12 transfected cells (2 × 104/well) were cocultured with 2 × 105/well PBMC. The panel shows the image of the different spots left on the wells at the end of assay: 1) pure red spots indicate cell lysis by IFN-γ non-producing cells; 2) pure blue spots indicate IFN-γ secreting cells; 3) violet spots indicate cell lysis by IFN-γ producing cells. Dark and light grey bars represent number of spots from DHD-K12-inoculated rats or from control rats respectively.