SYSTEME_IMMUNITAIRE

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When our body is faced with the intrusion of pathogens (likely to cause disease), it has a sophisticated arsenal of means of internal defenses: THE IMMUNE SYSTEM. A set of effective systems enabling it to ensure a coherent way its maintenance and protection. Just as a house must be designed and built to withstand the elements and intrusions, the body has elements able to fight against the attacks of viruses, bacteria or toxic substances.

This is the outer barrier of the skin to complex systems of physiological and chemical defense, intervening at the same inside the body. To maintain and encourage the process of defense, the body carries out "maintenance" naturally ... By producing new cells that replace those who have died or has become inoperable. In addition, certain organs such as bone (Picture 1: The fracture) and blood vessels can repair themselves in case of rupture.

Injury to a blood vessel, directly causes the contraction of smooth muscles in the walls (Circulatory Device), which narrows the gap and reduces the amount of blood that escapes. Specialized blood cells, called the PLATELETS or thrombocytes (Photo 2), also respond very quickly to any hemorrhagic lesion. They release chemicals that invigorate the muscles of the blood vessel strongly, extending their contraction. By staying contracted a few times for nearly twenty minutes, the muscles helps reduce the bleeding by forming a CAILLOT:

The formation of a blood clot may seem simple blood thickens damming the bleeding. Yet it is a complex process involving at least 35 chemical SUBSTANCES, reacting one with respect other in successive stages. Which results in the transformation of a soluble plasma protein, the FIBRINOGEN, into insoluble FIBRIN fibers:

Coagulation can be inhibited in any of its steps. This is what happens when D'HAEMOPHILIA, a hereditary disease affecting the proteins and enzymes responsible for clotting

The power and flexibility of the human brain capacity, greatly increase the number and effectiveness of our defenses against anything that can threaten our health. The role of our intelligence in this area is a bit like an architect capable of predicting the potential problems that might arise in a house, and take appropriate action. This is how a healthy lifestyle can reduce the risk of disease.

In spite of great diversity, the mechanisms involved in the human body to fight germs and parasites, disease vectors, can be divided into two broad categories:

A) INNATE DEFENSES: The wall of the skin is the front line of our innate defenses. But we also have a whole arsenal of weapons physiological, cellular and biochemical. Acting alone or in cooperation, these defenses are usually able to defeat the invaders. Physiological weapons are represented by all kinds of reflex reactions that destroy or expel unwanted organisms or substances scratching, sneezing, coughing, vomiting, tears ...

The expulsion of the undesirable substance is made possible by a thick liquid: The MUCUS secreted by cells that form the lining in the mouth, throat, lungs and reproductive system. This liquid slows the invasion of microbes and contains an antibacterial enzyme: The LYSOZYME. This enzyme, outside the mucus is also present in tears, saliva and breast milk. The action of lysozyme is to disaggregate MUREIN, a major component of the protective wall of most bacteria:

B) ADAPTIVE IMMUNE DEFENSES: The adaptive defenses such as ANTIBODY operate "finesse". They are generally selective, their specific action exerted only against a narrowly defined set of pathogens. They are really adaptive in the sense that the body triggers a nuanced way depending on each particular case.

An antibody combining two heavy chains and two light chains amino acid sequences, all assembled in the form of Y. Y is the base of a heavy chain, arms including two types of channels. It circulates in the blood and lymph. Some specialized cells interact closely in the fight against infectious agents:

Our immune system has more than one million different types of antibodies, ready to respond to any foreign intrusion! These are protein molecules that recognize a specific fragment of another protein (antigen), a stranger to his own biological environment. When the antibodies were detected and the invasion of foreign proteins, such as viruses, bacteria, fungi and parasites, the defensive mechanism of the immune system becomes active. The adaptive immune system is based on two types of defenses:

A) IMMUNITY Humoral: The cells that produce antibodies are specific white blood cells from the lymph areas, B LYMPHOCYTES:

Each B lymphocyte is a carrier of specific antibody molecules. It produces "copies" of the antibodies that bind to the outer wall, where they remain inert until they are activated by the presence of their specific antigen. When the millions of copies have been produced, most B cells stop dividing and become: PLASMA:

B) A CELL-MEDIATED IMMUNITY: The plasma cells release antibodies that millions constantly circulate in the blood and lymph. When they come into contact with an antibody that they are able to recognize, they attach themselves to him, signaling its presence to other parts of the immune system so that they are attacking. Major players in the cellular immunity, are LYMPHOCYTES T.

By binding to its target antigen, the antibody changes shape, which facilitates the identification and absorption of this couple (antibody-antigen, or hunter-prey), by a large white blood cell destructive germs named: MACROPHAGE , cell type APC

Below Macrophage in the lung (pink), which is preparing to absorb an infectious organism (green):

The process by which an antibody promotes phagocytosis of antigen by binding to it is called The OPSONIZATION. At the beginning of the chain, operates a so-called cell APC: Antigen Presenting Cell, which "devours" all foreign to the body. They work by absorbing bacteria or other pathogens, in a vesicle of the cytoplasm where they undergo the action of digestive substances. These substances disintegrate each bacterium absorbed protein fragments which it is composed, which fragments are not dangerous and can be used.

Instead of completely digest all these fragments and turn them into amino acids, the macrophages to repress their surface and combine with another molecule, a protein MHC: Major Histocompatibility Complex. And "marked", the foreign protein fragment can be detected by T lymphocytes AUXILIARY:

As soon as a helper T cell is bound to a protein fragment, it secretes a particular substance: the lymphokine. This is a chemical mediator release the active other types of T lymphocytes, B lymphocytes and phagocytes (macrophages), which destroy foreign elements in the body! Another substance that is secreted by the T helper cell, which is interferon inhibits viral proliferation.

The cellular immunity provided by phagocytes such as macrophages, which devour germs or cancer cells, also involves CYTOTOXIC T Lymphocyte cells. They destroy infected cells impregnating toxic molecules