CD200 and acute myeloid leukemia: To examine if the difference in T cell response between NPM1class I and NPM1class II instead could be mediated through checkpoint receptor signaling38, we analyzed the expression of checkpoint molecules on the surface of AML cells (PD-L1, PD-L2, VISTA, CD80, CD86, CD155, Galectin-9, CD47, and CD200) and T cells (CTLA4, LAG3, PD1, TIGIT, and TIM3) in diagnostic NPM1class I and NPM1class II BM samples using flow cytometry (Supplementary Fig. 25 and Supplementary Fig. 26).