What is immune system?
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The immune system is the system of specialized cells and organs that protect an organism from outside biological influences. (Though in a broad sense, almost every organ has a protective function - for example, the tight seal of the skin or the acidic environment of the stomach.) When the immune system is functioning properly, it protects the body against bacteria and viral infections, destroying cancer cells and foreign substances. If the immune system weakens, its ability to defend the body also weakens, allowing pathogens, including viruses that cause common colds and flu, to grow and flourish in the body. The immune system also performs surveillance of tumor cells, and immune suppression has been reported to increase the risk of certain types of cancer.
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The immune system consists of:\n\nSkin: without this so many things could enter your body and evidently kill you. Helps guard you from bacteria and viruses.\n\nTears and Mucus: Contain an enzyme called lysozyme. This breaks down the wall of lots of bacteria, but not all. \n\nSaliva: Anti-bacterial\n\nThe nasal passage and lungs are coated in mucus,  germs not killed instantly are trapped in the mucus and than swallowed.\n\nMast cells line the nasal passages, throat, lungs and your skin. Bacteria or a virus that wants to gain entry to your body must first make it past these and they are part of your defense system.\n\nYour immune system consists of these:\nSpleen - Replaces old red blood cells, and filters the blood looking for bad cells that shouldn't be in your body.\n\nThymus - This is between your breastbone and your heart. Contains or produces T-cells. This can be removed and you (adult) should be fine.\n\nLymph System - These are found in your neck and they get checked by your doctor to see if they are swollen. Filter out bacteria.\n\nWhite Blood Cells - Comes in 5 classes: Immunoglobulin A (IgA), E (IgE), G (IgG), D (IgD), M (IgM)\nDetects bad cells, binds to them and helps get rid of them.\n\nAntibodies\nComplement System\nHormones\nBone Marrow - Produces new white and red cells.
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There is no replacement for any part of the immune system but you can boost your immune system with proper diet and supplementation, ask your physician to refer you to a nutritionist with your concerns.
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lymph nodes are a part of your immune system & when they swell, it's usually them trying to fight off an infection
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Lymph nodes, also incorrectly called "Lymph glands" (they do not secrete anything and are therefore not glands), are components of the lymphatic system. Lymph nodes act as filters, with an internal honeycomb of connective tissue filled with lymphocytes that collect and destroy bacteria and viruses. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes. Humans have approximately 500-600 lymph nodes. Clusters of lymph nodes are found in the underarms, groin, neck, chest, and abdomen
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A lymphocyte is a type of white blood cell involved in the vertebrate immune system..\n\n  u will find more in the given source..
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I don't usually use Wikipedia but it's got a great article on what exactly those things are!\n\nSee below:\n\nLymph nodes, also incorrectly called "Lymph glands" (they do not secrete anything and are therefore not glands), are components of the lymphatic system. Lymph nodes act as filters, with an internal honeycomb of connective tissue filled with lymphocytes that collect and destroy bacteria and viruses. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes. Humans have approximately 500-600 lymph nodes. Clusters of lymph nodes are found in the underarms, groin, neck, chest, and abdomen.\n\nFor more see: \n\nhttp://en.wikipedia.org/wiki/Lymph_node
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antibody immune response.\n\nits an antibody, its foreign; new to the body.
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Lymph nodes are part of a  lymph vessel system that branches throughout the human body. There are about 100 (not sure if anyone has counted them all) that end up at a point called a 'lymph node'. The lymph vessel system is part of the immune system. It's job is to filter the body of foreign debris and than at some point returns back to the blood stream. Microscopic cancer cells that seed from a 'primary tumor' have the ability to enter the lymphatic system and travel throughout the body and lodge almost anywhere.\nSome notable locations for the lymph nodes are  neck, groin, armpit,  central chest, and abdominal cavity. \n\nLymphatic System\nhttp://en.wikipedia.org/wiki/Lymphatic_system\n\nLymph Node\nhttp://en.wikipedia.org/wiki/Lymph_node
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Through a series of steps called the immune response, the immune system attacks organisms and substances that invade our systems and cause disease. The immune system is made up of a network of cells, tissues, and organs that work together to protect the body.\n\nThe cells that are part of this defense system are white blood cells, or leukocytes (pronounced: loo-kuh-sytes). They come in two basic types (more on these below), which combine to seek out and destroy the organisms or substances that cause disease. \nThe leukocytes circulate through the body between the organs and nodes by means of the lymphatic (pronounced: lim-fah-tik) vessels. (You can think of the lymphatic vessels as a type of highway between the rest stops that are the lymphoid organs and lymph nodes). Leukocytes can also circulate through the blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for substances that might cause problems.A foreign substance that invades the body is called an antigen (pronounced: an-tih-jun). When an antigen is detected, several types of cells work together to recognize and respond to it. These cells trigger the B lymphocytes to produce antibodies. Antibodies are specialized proteins that lock onto specific antigens. Antibodies and antigens fit together like a key and a lock.Once the B lymphocytes have produced antibodies, these antibodies continue to exist in a person's body. That means if the same antigen is presented to the immune system again, the antibodies are already there to do their job.Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That is the job of the T cells. The T cells are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (There are actually T cells that are called "killer cells"). T cells are also involved in helping signal other cells (like phagocytes) to do their jobs.\n\nAntibodies can also neutralize toxins (poisonous or damaging substances) 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.\n\nAll of these specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity. Humans have three types of immunity - innate, adaptive, and passive.
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Allergies are the body's inappropriate reaction to a normally benign protein, which the body sees as an invader. Note that allergies are ALWAYS to a protein. Intolerances as well as sensitivities are different from allergies in that it is not necessarily to a protein - such as lactose intolerance - but can produce similar symptoms.\n\nThe immune system is designed to watch for and attack invading cells which come into our bodies, such as viruses and bacteria. Sometimes, though, the immune system sees something which isn't bad for us, such as pollen, dander, even foods, as an invader, and it goes on the attack. Mast cells rush to the scene, releasing their load of chemicals, and calling in other inflammatory cells of the immune system, such as basophils and Killer T-cells. All the chemicals these cells release are what cause the symptoms of allergy, including hives, running nose, itchy eyes, sneezing, coughing, etc. One of the main chemicals involved is histamine, which is why antihistamines (also known as histamine blockers) are prescribed for allergies.
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It's complex.  Basically the virus infects cells, and the viral protein is present on the cell surface by MHC molecules.  The circulating T cells then can latch on to and identify the virus-infected cell as foreign.  That specific T-cell then proliferates, and starts hunting down infected cells.  There is alot more going on, including antibody production and release by B cells.\n\nWell described in this book chapter.
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The spleen is a gland that is associated with the circulatory system, where it functions in the destruction of old red blood cells in holding a reservoir of blood.
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The human spleen is an organ that creates lymphocytes for the destruction and recycling of old red-blood cells. The spleen is also a blood reservoir. It supplies the body with blood in emergencies such as a bad cut. The speen is also the location where white blood cells trap organisms.
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Antigen is any substance that evokes the production of an antibody when introduced into the body. Antigens can enter the body through the respiratory tract, digestive tract, or skin. The most common antigens are proteins such as those found in/on bacteria and viruses.While an antibody Antibody, any of perhaps a million kinds of normally occurring protein molecules that are produced in the body of cells called lymphocytes and that act primarily as a defence against invasion by foreign substances. An important component of the immune system, antibodies are found in the blood of all vertebrates, in the fraction of the blood called gamma globulin.
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AIDS is an abbreviation for an immunity deficiency syndrome. With aids, your lungs usually become infected to the point of pneumonia (fluid build up). The infection that causes the fluid can not be treated because your immune system is shot. The fluid builds up until you can no longer breathe. You drown and die. It is sad. And it is - for now - a hopeless disease.
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T-cells are a part of the immune system.  They attack viruses and bacteria as a predator attacks prey.