Pub. date: 2008 | Online Pub. Date: April 21, 2008 | DOI: 10.4135/9781412963855 | Print ISBN: 9781412941860 | Online ISBN: 9781412963855| Publisher:SAGE Publications, Inc.About this encyclopedia
Immune System and Disorders
The immune system protects the body from invasion by nonself organisms with an array of tissues, cells and organs working together through primary and secondary mechanisms. The primary line of defense is physical and chemical barriers to keep out invaders. The skin forms a tough physical barrier and secretes oil and sweat as chemical defenses. Other chemical defenses are the acid secretions in the stomach and vagina, mucous secretions in the respiratory tract and lysozymes (antibacterial enzymes) in tears. Colonies of friendly bacteria live in the intestines to use up nutrients invaders could thrive on. The flushing action of urine removes invaders from the urinary tract. If an invader makes it past the first line of defense, a two-pronged secondary attack with nonspecific and specific responses is triggered into action. The nonspecific response is direct and immediate with chemical and cellular agents. The specific response is complex, specific to the ...