Mechanisms of immune escape at relapse. (A) Summary of mechanisms of immune escape observed in each relapsing patient. (B) Expression of PD-L1 as estimated by IHC in relapsing tumors obtained from patients 3 and 6. Original magnification ×400. (C) MRI imaging in 3 individuals demonstrating extramedullary (immune-privileged anatomic site) relapses. (D) Representative flow cytometry plot from patient 1 depicting loss of HLA-DR expression at relapse. (E) Downregulation of expression of target TAAs (WT1, PRAME, Survivin) on relapsing AML/MDS cells in patient 7. IHC; original magnification, ×400.