Increased frequency of IFN-γ-secreting CD8+ T cells after p.o./i.v. Salmonella infection of C57BL/6 mice (n = 3). For each group, 1 mouse was assessed individually and the remaining splenocytes from 2 mice were pooled in an equivalent proportion. 1 × 106 spleen cells restimulated with either wild-type EL-4 (EL-4) or C-Raf overexpressing EL-4 cell (EL-Raf) and not stimulated (NST) were used. Production of IFN-γ was determined by flow cytometry after CD8 surface staining and intracellular IFN-γ staining. Each data point represents the proportion of IFN-γ positive cells for one individual mouse or two pooled mice respectively. Intracellular staining with an FITC-conjugated isotype control mAb always resulted in <0.05% positive cells.