While programmed cell death 1 ligand 1 (PD-L1) expression was not detected on leukemic T cells (data not shown), PD-L1 was found to be expressed in a significant fraction of non-T-cell host immune cells, presumably myeloid cells, in T-ALL5-bearing C57BL/6 mice relative to non-tumor-bearing wild-type mice (Fig. 5C); a more moderate increase in PD-L1 expression was seen for T-ALL3 (Fig. 5D). The gene discussed is CD274; the disease is neoplasm.