JAK1 and neoplasm: IL-2Rα (also known as p55 or CD25) binds to IL-2 with low affinity; IL-2Rβ (also known as p75 or CD122) mainly binds to Janus kinase 1 (JAK1) and is essential to the active signal transducer and activator of transcription 5 (STAT5); IL-2Rγ (also known as p64 or CD132) is essential for proliferative signaling, but the γ subunit alone does not show affinity for IL-2.213 Based on the function of IL-2, the development of fusion proteins that selectively favor the activation of IL-2Rβγ, but not IL-2Rα, may specifically activate T cells or NK cells to kill tumor cells while preventing side effects.