 One strategy that has received attention is treatment with cytokines such as IL-2 to enhance anti-tumor immunity. IL-2 has stimulatory effects on a number of immune cell types including T and B cells, monocytes, macrophages, lymphokine-activated killer cells LAK and natural killer NK cells. Based on the ability of IL-2 to provide durable curative anti-tumor responses, systemic administration of IL-2 has been approved to treat patients with metastatic melanoma or renal carcinoma. Unfortunately, the considerable toxicity associated with this treatment makes it difficult to achieve an effective dose at the site of the tumor and limits the population that can be treated. Thus, there is critical need for innovative strategies that enhance the effects of IL-2, to reduce its toxicity without compromising the clinical benefit, and to treat other diagnoses. 