Biological response modifiers (BRMs) are substances that modify immune responses. They can be both endogenous (produced naturally within the body) and exogenous (as pharmaceutical drugs), and they can either enhance an immune response or suppress it. Some of these substances arouse the body's response to an infection, and others can keep the response from becoming excessive. Thus they serve as immunomodulators in immunotherapy (therapy that makes use of immune responses), which can be helpful in treating cancer (where targeted therapy often relies on the immune system being used to attack cancer cells) and in treating autoimmune diseases (in which the immune system attacks the self), such as some kinds of arthritis and dermatitis. Most BRMs are biopharmaceuticals (biologics), including mon