In an ALL mouse model, inhibition of MERTK significantly decreases the expression PD-L1/L2 on CD11b+ monocytes/macrophages and PD-1 on CD4+ and CD8+ T cells in the leukemic microenvironment, reducing the incidence of splenic FOXP3+ Tregs at sites of leukemic infiltration. Here, CD274 is linked to acute lymphoblastic leukemia.