IL2 and cancer: Based on observations that immune stimulation can be associated with spontaneous regression of cancer, numerous antigen-non-specific immunotherapy approaches have been introduced that are directed against cell-surface molecules, receptors, and immune effector pathways including Bacillus Calmette–Guérin (BCG), interleukin-2 (IL-2), interferons, CpG oligonucleotides, enzyme inhibitors targeting immune regulatory pathways, and antibodies against receptors involved in immune tolerance such as anti-CTLA-4 and anti-PD-1/PD-1 ligand antibodies [2].