Recombinant interleukin (IL)-2 is a newly approved immunoregulatory pr
otein produced by lymphocytes that exhibits a wide range of immunologi
c effects. It is a true biologic response modifier in that is has no k
nown direct antitumor activity, but mediates its cytotoxicity through
activation of effector cells including T cells, natural killer cells,
and lymphokine-activated killer cells. Recombinant IL-2 has demonstrat
ed activity in patients with renal cell carcinoma and melanoma, with o
bjective response rates of approximately 15-20%. The median duration o
f response in renal cell carcinoma is 23 months. Toxicity experienced
with high-dose IL-2 can be significant. The most common dose-limiting
toxicities are hypertension, weight gain, oliguria, respiratory insuff
iciency, and neurotoxicity. These effects are generally manageable and
reversible on discontinuation of therapy. Administration of low-dose
IL-2 has emerged as a means of substantially reducing toxicity. At lea
st in renal cell carcinoma, it appears that the response rate to low-d
ose IL-2 is comparable to that with higher dosages.