CTLA4 and cancer: Non-specific immunotherapies stimulate or boost the immune system but do not target cancer cells directly through the use of certain cytokines, including IL2, IL-7, IL-12, IL-21, and IFN-α/β/γ, and the checkpoint inhibitors PD-1, PD-L1, and CTLA-4, and immuno-stimulatory agents such as CpG oligonucleotides, and agonistic CD40 are an example of nonspecific immune therapy and have sometimes led to a better immune response against cancer cells.