The immune system, which is made up of proteins, tissues, special cells, and organs, vindicates people against microorganisms and germs every day. In most instances, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to infections and illnesses. The immune system is the body's defence against infectious disease. Through a series of steps named the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.
The immune system is composed of a network of tissues, organs and cells that work together to protect the body. The cells involved are white blood cells, or leukocytes, which come in two basic types that combine to pick out and dismantle substances or disease-causing organisms.
Leukocytes are stored or produced in many locations in the body, comprising the thymus, and bone marrow. For this reason, they are called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily as lymph nodes, that house the leukocytes.
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The leukocytes circulate through the body between the nodes and organs through the lymphatic vessels and blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for substances that might causes problems.
The two basic types of leukocytes are:
1. lymphocytes, cells that allow the body to remember and recognize previous invaders and help the body destroy them
2. phagocytes, cells that chew up invading organisms
A number of different cells are considered phagocytes. The most common type is the neutrophil, which primarily fights bacteria. The two types of lymphocytes are T lymphocytes and B 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 mellow into T cells. B lymphocytes and T lymphocytes have different functions: T cells defeat the invaders that the intelligence system has recognized. B lymphocytes single out their destinations and sending defences to occlude onto them.
The immune reaction takes place as follows, when antigens are detected, several types of cells work together to recognize them and respond. Those cells cause the B lymphocytes to produce antibodies, particular proteins that lock onto specific antigens.
If the antibodies are produced they are 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 for example if someone gets sick with a certain disease like chickenpox, than typically the person won't get sick from it again.
Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That's the job of the T cells, which are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (Some T cells are actually called "killer cells.") T cells also are involved in helping signal other cells (like phagocytes) to do their jobs.
Antibodies also can neutralize toxins which are produced by different organisms. Lastly, antibodies can activate a group of proteins called complement that are also part of the immune system. Complement assists in killing bacteria, viruses, or infected cells.
All of these specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity.
The defence of parasites in which in the essentials mast's cells, Eosinophile and Basophile are involved forms a special case of the innate immune response. These cells store toxic substances in numerous granules, and on their surfaces, receptors related to antibodies of the IgE subtype. However, they are dependent on the preparatory work of the specific immune system, first noticed an infestation and then produce specific IgE antibodies that bind to the parasite and it opsonize. The cells now recognize in the opsonized parasites and pour in the immediate vicinity of the toxic substances that damage the parasite in different ways and ultimately bring about his death. The innate immune response responds certainly very quickly to an infection, it changes not, however, and after re infection with the same pathogen as effective - or ineffective - run as the first time an "immunological memory" that a more effective response to a possible re-infestation and is based on the protective effect of vaccination cannot be trained by the innate immune response, but remains an exclusive feature of the acquired immune response.
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Parasites live either outside or inside the cells. The T-cell responses can be triggered by intracellular parasites such as the organism that causes malaria. Extracellular parasites are often much larger than viruses or bacteria and needs a much broader immune attack. Parasitic infections often trigger an inflammatory response when basophils, eosinophils, and other specialized granular cells rush to the scene and release their stores of toxic chemicals in an attempt to destroy the invader. So the antibodies also play a role in this attack,pleasing the granular cells to the site of infection.
Once a person is bitten and infected, it is only a matter of time before the individual experiences the parasite's wrath. Symptoms usually appear in three stages: chills, followed by fever, and then sweating. Signs of malaria first begin to emerge 10 to 16 days after the mosquito bite, the same time which red blood cells are bursting. The infected person starts to experience chills, along with headache, nausea, and vomiting. Within an hour or two, the person's temperature rises, and the skin feels hot and dry. Then, as the body temperature falls, drenching sweat begins. Eventually, the person grows tired and weak and is likely to fall asleep.So the malaria infection is caused by an Anopheles mosquito which carries the malaria parasite while it takes a blood meal. Then the human host is injected in the form of sporozoites. The plasmodium parasite circulates in the bloodstream and tries to find its way into the liver where it can begin to multiply. This happens without being detecting. During this period, the parasite prolongs its survival by quickly attaching to and entering red blood cells. Malaria-infected red blood cells disable dendritic cells and prevent them from launching an effective attack against the infection. While hiding inside the red blood cell host, they are protected and shielded from detection by the human host's immune system and continue to form daughter parasites, known as merozoites, without causing any detectable symptoms. Finally, after 48 hours the infected red blood cells burst releasing the merozoites into the bloodstream where they wait for another mosquito to transfer them to their next human host to repeat the whole cycle once again.
Multiply of sporozoites
Malarial parasites put the human immune defence on a hard test with her conversion cord. The most effective defensive strategy consists in intercepting the parasite's stadia freely swimming in the bloodstream (Sporozoiten, Merozoiten, Gametozyten) help of antibodies. Indeed, the defence must lead a Mehrfrontenkampf, because three parasite's stadia have different covers and, moreover, change over and over again her surface structures (antigens). Hence, many of the produced antibodies are lost because they do not find the suitable attack targets (antigens). An effective immune answer is also complicated by the fact that the parasites most time stay inside from body cells. Sporozoites increases in the liver. In this hiding place they can be fought only by t-killer cells (cytotoxic t cells). However, after all what one knows up to now, this form of the defence is with malarial parasites only limits efficiently. The Merozoites still go forward more ingenious. They increase in red blood cells. In contrast to other cells the red blood cells lack the MHC I molecules with which they could present fragments of the parasite in her surface. The killer cells lack simply the necessary "enemy's pictures", hence, they cannot intervene. Another trick still belongs to the survival strategy of the Merozoites: They make the infected red blood cells train certain surface molecules. These molecules work like "pastes" and fix the blood cells to the vascular wall. Thus an evacuation is prevented in the spleen which ordinarily removes ill blood cells. The Merozoites are in the "parking" Erythrocytes in security and can increase in complete silence. The malarial parasites know even how to use preventive measures of the body for her advantage. As a reaction to the illness causes, killer cells release the messenger's material TNF Î± (tumour necrosis factor alpha). In low concentration the parasites are killed. Nevertheless, with excess of a certain concentration the paste effect is strengthened. More and more red blood cells, also non-infected, get stuck on the vascular wall and get lumpy with each other. The traffic jam in the blood vessels is still strengthened by antibodies which fix to the "paste molecules" of the infected blood cells. What uses the malarial parasite - they increase best of all in low in oxygen surroundings - can become for the person the mortal danger. Defective oxygen transport and insufficient blood circulation destroy organs like liver, kidney or brain.
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