PDCD1 and diffuse intrinsic pontine glioma: As PD-L2 is highly expressed on antigen presenting cells and T lymphocytes, has greater (more than fourfold) affinity to PD-1 compared with PD-L1, and is similarly responsible for blocking T-cell response [43, 64], PD-1 inhibition (as opposed to PD-L1 inhibition) may be a more efficacious immunotherapeutic target in this subset of DIPG patients.