The innate immune system, also known asnon-specific immune system and first line of defense, is a subsystem of the overall immune system that comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner. This means that the cells of the innate system recognize and respond to pathogens in a generic way, but, unlike the adaptive immune system, it does not create long-lasting or protective immunity to the host.
The innate immune response to infectious and sterile injury is regulated by neural systems that control cytokine production. The Inflammatory Reflex is a prototypical neural system that controls cytokine production in the spleen. Action potentials transmitted through the vagus nerve to spleen regulate the release of acetylcholine, the neurotransmitter that inhibits cytokine release by interacting with alpha7 nicotinic acetylcholine receptors expressed on cytokine-producing cells. This controls the process of inflammation around an injury such as a cut or scratch.
Innate immune system functions include :
gathering cells to infectious areas through the production of chemical factors that include chemical mediators called cytokines.
Activate the compliment cascade to identify pathogens, and promote the clearance of bacteria.
2. Activates T and B cells in response to an infectionLeukocytes are produced or stored in many locations in the body, including the thymus, spleen, and bone marrow. For this reason, they're called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily as lymph nodes, that house the leukocytes. These Leukocytes play an important role in the immune a system, mostly because they are in charge of recognizing and destroying invaders.
There are two types of Leukocytes:
phagocytes, cells that chew up invading organisms, and lymphocytes, cells that allow the body to remember and recognize previous invaders and help the body destroy them.
The two kinds of lymphocytes are B lymphocytes and T lymphocytes. Lymphocytes start out in the bone marrow and either stay there and mature into B cells, or they leave for the thymus gland, where they mature into T cells. B cells identify and contain information about foreign invaders, while T cells attack and destroy.
The histocombatibillity complex (hcm 2) is what delivers the antigen to the B cells and T cells.
When antigens (foreign substances that invade the body) are detected, several types of cells work together to recognize them and respond. These cells trigger the B lymphocytes to produce antibodies, specialized proteins that lock onto specific antigens.
Once produced, antibodies continue to exist in a person's body, so that if the same antigen is presented to the immune system again, the antibodies are already there to do their job. So if someone gets sick with a certain disease, like chickenpox, that person typically doesn't get sick from it again. These antibodies also help to quicken the pase of the immune systems response by avoiding the use of phagocytes (cells that "present" pathogens to B cells).
This is also how immunizations prevent certain diseases. An immunization introduces the body to an antigen in a way that doesn't make someone sick, but does allow the body to produce antibodies that will then protect the person from future attack by the germ or substance that produces that particular disease.
4. Distinguishes self from nonself
T cells compare non-self antigens to HLA (human leukocyte antigens) molecules with proteins the system already knows are its own. Your T-cells don't react to your HLA because of tolerance caused by the memory of the Tand B cells, but are not tolerant to the HLA proteins of someone else. Thus, when there is a non-self system in your body (i.e.: after a transplant or infection), your T-cells will begin a cell-mediated immune response against it, considering them foreign.
Sources:
http://m.kidshealth.org/parent/general/body_basics/immune.html
http://www.nlm.nih.gov/medlineplus/ency/article/000821.htm
http://en.m.wikipedia.org/wiki/File:Innate_immune_system.png
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