NIH -- Treating cancer patients with interleukin-7 (IL-7), a small protein that can stimulate the immune system, leads to an increase in lymphocytes, key to the production of effective immune responses, in the body, according to a new study by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health (NIH). The demonstration that IL-7 is able to broaden the possible immune responses in humans could have a wide range of clinical implications. This study was published online June 23, 2008, in The Journal of Experimental Medicine.