Interleukin-2 (IL-2) is a well-characterized growth factor for immune effector cells which play critical roles in tumor control and rejection. A recombinant human IL-2 has been approved for treating metastatic melanoma and renal cell carcinoma. However, the major drawback of IL-2 therapy is its severe systemic toxicity. As a result, use of high dose IL-2 is limited to specialized programs with experienced personnel and it is generally offered to patients who are responsive and have excellent organ function. Thus, there is a critical need for innovative strategies that enhance the effects of IL-2 or reduce its toxicity without compromising clinical benefits.