CD4 and acute myeloid leukemia: The expanded T cells were co-cultured with their respective autologous IFN-γ treated AML or MPAL blasts; 4-1BB was upregulated on CD8+ and/or CD4+ populations in 13 AML cases, which correlated with an increase in IFN-γ production and OX40 expression by CD4+ T cells (Fig. 2B, Supplementary Fig. 7A).