Interferon is a glycoprotein produced especially in white blood cells in response to stimuli such as exposure to virus, bacterium, or parasite. Humans make endogenous (self-made) interferon in relatively small amounts. Exogenous (made outside the body, as by the pharmaceutical industry) interferon may be administered to assist in fighting infection or cancer. In laryngology, interferon has been used against HPV infection that causes recurrent respiratory papillomatosis (RRP).