CD8A and leukemia: After 4 hours of co-cultivation, the frequencies of IFN-γ+ cells among CD8+ T cells were significantly higher in samples co-cultured with R54low leukemia cells than in those co-cultured with R54high cells (31.8 ± 1.0% vs. 25.3 ± 0.7%, p<0.05) (Fig 5B).