THE IMMUNE SYSTEM
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- Your body's cells have proteins that are antigens. These include a group of antigens called HLA antigens. Your immune system learns to see these antigens as normal and usually does not react against them.
- The Immunity System
- Innate, or nonspecific, immunity is the defense system with which you were born. It protects you against all antigens. Innate immunity involves barriers that keep harmful materials from entering your body. These barriers form the first line of defense in the immune response. Examples of innate immunity include:cough reflexEnzymes in tears and skin oilsMucus, which traps bacteria and small particlesSkinStomach acid
- The immune response is how your body recognizes and defends itself against bacteria, viruses, and substances that appear foreign and harmful.
- The immune system protects the body from possibly harmful substances by recognizing and responding to antigens. Antigens are substances (usually proteins) on the surface of cells, viruses, fungi, or bacteria. Nonliving substances such as toxins, chemicals, drugs, and foreign particles (such as a splinter) can also be antigens. The immune system recognizes and destroys, or tries to destroy, substances that contain antigens.
- If an antigen enters the body and B-cells recognize it (either from having had the disease before or from being vaccinated against it), B-cells will produce antibodies. When antibodies attach to an antigen (think a lock–key configuration), it signals other parts of the immune system to attack and destroy the invaders.
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