Many allergic reactions are caused by the body's immune response to normally harmless environmental substances. The immune system is designed to protect against pathogens such as microscopic organisms and foreign substances that arise from outside the body. Our immune system normally protects from cancer cells that arise within our bodies. In auto-immune diseases, the immune system may start to attack some of the body's own cells. Antigen-antibody responses are normally very specific.
Cancer can result from a gene mutation that produces uncontrolled cell division.
Biological research generates knowledge used to design ways of diagnosing, preventing, treating, controlling, or curing diseases of plants and animals. The effects of diseases caused by poor personal choices show up immediately. Diseases may be caused by inheritance, toxic substances, poor nutrition, organ malfunction, and personal behavior. Failure to maintain homeostasis will usually result in good health. Free-Response Section 1.