Cytokines

Cytokines are the messages immune cells use to talk to each other. In cancer treatment, two families are used in synthetic form. Interferons, such as interferon alfa, can enhance the immune response by activating certain white blood cells and can also slow the growth of cancer cells themselves. Interleukin-2 (IL-2) boosts the numbers of white blood cells, including killer T cells and natural killer cells, which can attack tumour cells; it may also increase antibody production. Because a cytokine sends a body-wide alarm signal rather than targeting one tumour marker, its effects are broad: flu-like symptoms such as fever, chills and fatigue are common, and high doses of cytokines can cause breathing problems, dangerously low or high blood pressure and organ damage, so this treatment requires careful monitoring. Cytokines belong to the wider group of immune system modulators, which also includes BCG (a weakened tuberculosis bacterium instilled into the bladder in bladder cancer) and immunomodulatory drugs such as lenalidomide, which among other actions prompt cells to release IL-2 — these are described by NCI on the same page.