Radioprotection with cytokines--learning from nature to cope with radiation damage.

The quest for methods to protect cells from the damaging effects of ionizing radiation led to the observation that cytokines, endogenously produced hormone-like polypeptides, are radioprotective. Interleukin-1 and tumor necrosis factor-alpha, given before irradiation, can protect mice from doses of radiation that would be fatal to untreated animals. At lower doses of radiation, the hemopoietic growth factors, interleukin-1, interleukin-4, interleukin-6, tumor necrosis factor-alpha, interferon, and leukemia inhibitory factor can promote recovery when administered after irradiation. Exposure to ionizing radiation selectively induces expression of some cytokines. Recent work suggests that certain cytokines may initiate autocrine/paracrine regulated recovery and repair pathways. Thus, the radioprotective and therapeutic effects of supplementary pharmacological doses of cytokines may act by amplifying innate defenses to ionizing radiation.