PDCD1LG2 and leukemia: Host Mertk knockout or pharmacologic inhibition reduced PD-L1 and PD-L2 expression levels by leukemia-associated macrophages in an AML model [66], and by CD11b+ myeloid cells in a B-ALL model [65], while also reducing T-cell exhaustion in these leukemias in vivo and in ex vivo co-culture systems [65,66,67].