IL2 and neoplasm: The advantages of using this conjugated form of the IL-2 are that, on the one side, is released in a controlled way in the tumor’s proximity, avoiding systemic toxic effects; and on the other side, PEG conjugation prevents IL-2 binding to the IL2Ralpha subunit (and the subsequent activation of CD4-positive regulatory immunosuppressive T cells), while IL2Rbeta activation plays a key role on the proliferation and activation of effector T cells (314).