CD28 and leukemia: In 15 out of 23 patients, we observed an increase of leukemia-reactive IFN-γ-producing CD8+ T cells (Figure S1 in Supplementary Material) mostly belonging to effector memory (EM) and EM expressing CD45RA (effector memory expressing RA) subsets (Figure S2 in Supplementary Material), which highly expressed the activation marker CD38 and downregulated CD28 as compared to naïve (p = 0.03) or central memory (CM) (p = 0.03) T cells.