CD4 and chronic myelogenous leukemia, BCR-ABL1 positive: Zheng et al. have shown in a murine model of chronic myeloid leukaemia that donor memory CD4+ T cells (CD4+CD62L−CD44+CD25−) can kill leukaemic cells without causing GvHD, as opposed to the action of naïve cells that cause GvHD (140).