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Lymph nodes are glands that play an important part in your body's defense against infection. They produce lymph, which travels throughout your body in the lymph system, and filters impurities from the body. Common areas where the lymph nodes can be felt (with the fingers) include: Groin Armpit Neck (there is a chain of lymph nodes on either side of the front of the neck, both sides of the neck, and down each side of the back of the neck) Under the jaw and chin Behind the ears On the back of the head Lymph nodes can become swollen from infection, inflammatory conditions, an abscess, or cancer. Other causes of enlarged lymph nodes are rare. By far, the most common cause of swollen lymph nodes is infection. When swelling appears suddenly and is painful, it is usually caused by injury or an infection. Enlargement that comes on gradually and painlessly may, in some cases, result from cancer or a tumor. Common Causes Return to top Infections that commonly cause swollen lymph nodes include mononucleosis, German measles (rubella), tuberculosis, mumps, ear infection, tonsillitis, an abscessed or impacted tooth, gingivitis (swelling of the gums), mouth sores, and sexually transmitted diseases. Immune or autoimmune disorders that can cause swollen lymph nodes include rheumatoid arthritis and HIV. Cancers that can cause swollen glands include leukemia, Hodgkin's disease, or non-Hodgkin's lymphoma. Which lymph nodes are swollen depends on the type of problem and the body parts involved. Identifying the location can help determine the possible cause. Swollen lymph nodes may also be caused by some medications (like phenytoin for seizures) or certain vaccinations (namely, typhoid). The Body's First Line of Defense The immune system is a complex of organs--highly specialized cells and even a circulatory system separate from blood vessels--all of which work together to clear infection from the body. The organs of the immune system, positioned throughout the body, are called lymphoid organs. The word "lymph" in Greek means a pure, clear stream--an appropriate description considering its appearance and purpose. Lymphatic vessels and lymph nodes are the parts of the special circulatory system that carries lymph, a transparent fluid containing white blood cells, chiefly lymphocytes. Lymphatic vessels form a circulatory system that operates in close partnership with blood circulation. Lymph bathes the tissues of the body, and the lymphatic vessels collect and move it eventually back into the blood circulation. Lymph nodes dot the network of lymphatic vessels and provide meeting grounds for the immune system cells that defend against invaders. The spleen, at the upper left of the abdomen, is also a staging ground and a place where immune system cells confront foreign microbes. Organs and tissues of the immune system dot the body in a protective network of barriers to infection. Pockets of lymphoid tissue are in many other locations throughout the body, such as the bone marrow and thymus. Tonsils, adenoids, Peyer's patches, and the appendix are also lymphoid tissues. Both immune cells and foreign molecules enter the lymph nodes via blood vessels or lymphatic vessels. All immune cells exit the lymphatic system and eventually return to the bloodstream. Once in the bloodstream, lymphocytes are transported to tissues throughout the body, where they act as sentries on the lookout for foreign antigens. How the Immune System Works Cells that will grow into the many types of more specialized cells that circulate throughout the immune system are produced in the bone marrow. This nutrient-rich, spongy tissue is found in the center shafts of certain long, flat bones of the body, such as the bones of the pelvis. The cells most relevant for understanding vaccines are the lymphocytes, numbering close to one trillion. The two major classes of lymphocytes are B cells, which grow to maturity in the bone marrow, and T cells, which mature in the thymus, high in the chest behind the breastbone. B cells produce antibodies that circulate in the blood and lymph streams and attach to foreign antigens to mark them for destruction by other immune cells. B cells are part of what is known as antibody-mediated or humoral immunity, so called because the antibodies circulate in blood and lymph, which the ancient Greeks called, the body's "humors." B cells become plasma cells, which produce antibodies when a foreign antigen triggers the immune response. Certain T cells, which also patrol the blood and lymph for foreign invaders, can do more than mark the antigens; they attack and destroy diseased cells they recognize as foreign. T lymphocytes are responsible for cell-mediated immunity (or cellular immunity). T cells also orchestrate, regulate and coordinate the overall immune response. T cells depend on unique cell surface molecules called the major histocompatibility complex (MHC) to help them recognize antigen fragments. Antibodies Antibodies produced by cells of the immune system recognize foreign antigens and mark them for destruction. The antibodies that B cells produce are basic templates with a special region that is highly specific to target a given antigen. Much like a car coming off a production line, the antibody's frame remains constant, but through chemical and cellular messages, the immune system selects a green sedan, a red convertible or a white truck to combat this particular invader. However, in contrast to cars, the variety of antibodies is very large. Different antibodies are destined for different purposes. Some coat the foreign invaders to make them attractive to the circulating scavenger cells, phagocytes, that will engulf an unwelcome microbe. When some antibodies combine with antigens, they activate a cascade of nine proteins, known as complement, that have been circulating in inactive form in the blood. Complement forms a partnership with antibodies, once they have reacted with antigen, to help destroy foreign invaders and remove them from the body. Still other types of antibodies block viruses from entering cells. T Cells T cells have two major roles in immune defense. Regulatory T cells are essential for orchestrating the response of an elaborate system of different types of immune cells. Helper T cells, for example, also known as CD4 positive T cells (CD4+ T cells), alert B cells to start making antibodies; they also can activate other T cells and immune system scavenger cells called macrophages and influence which type of antibody is produced. Certain T cells, called CD8 positive T cells (CD8+ T cells), can become killer cells that attack and destroy infected cells. The killer T cells are also called cytotoxic T cells or CTLs (cytotoxic lymphocytes). Immune system process Activation of helper T cells T lymphocytes become CD4+ or helper T cells, or they can become CD8+ cells, which in turn can become killer T cells, also called cytotoxic T cells. After it engulfs and processes an antigen, the macrophage displays the antigen fragments combined with a Class II MHC protein on the macrophage cell surface. The antigen-protein combination attracts a helper T cell, and promotes its activation. Activation of cytotoxic T cells After a macrophage engulfs and processes an antigen, the macrophage displays the antigen fragments combined with a Class I MHC protein on the macrophage cell surface. A receptor on a circulating, resting cytotoxic T cell recognizes the antigen-protein complex and binds to it. The binding process and a helper T cell activate the cytotoxic T cell so that it can attack and destroy the diseased cell. Activation of B cells to make antibody A B cell uses one of its receptors to bind to its matching antigen, which the B cell engulfs and processes. The B cell then displays a piece of the antigen, bound to a Class II MHC protein, on the cell surface. This whole complex then binds to an activated helper T cell. This binding process stimulates the transformation of the B cell into an antibody-secreting plasma cell. Top of Page Last updated September 25, 2003 (alt) In healthy people, the spleen plays a role in immunity against bacterial infections. The spleen is in the uppermost area of the left side of the abdomen, just under the diaphragm. It typically has attachments to the stomach, left kidney, and colon. If the surgery is elective (planned) rather than an emergency, your doctor will give you vaccines against certain bacteria prior to removing the spleen. If the operation is an emergency, you should get the vaccines after the operation. The spleen is removed while the patient is under general anesthesia. The surgeon makes an incision in the abdomen, locates the spleen, and separates it from its attachments to the surrounding organs. The surgeon then divides the blood supply to the spleen and removes it from the abdomen. After a careful check for bleeding, the abdominal incision is closed. Some patients may be able to undergo laparoscopic surgery (also known as "keyhole" or "telescopic" surgery) to remove the spleen. This operation is done with several tiny incisions instead of a single large one, and recovery is typically faster. Some patients, however, are not suited to laparoscopic surgery. Thymus The thymus gland lies in the upper part of the mediastinum behind the sternum and extends upwards into the root of the neck. It weighs about 10 to 15 g.(about half an ounce) at birth and begins to grow until the individual reaches puberty when it begins to atrophy. It’s maximum weight is around 30 - 40g (around 1 to 1.5 ounces) by the age of 40 it has returned to it’s weight at birth. The thymus consists of two lobes connected by areolar tissue. The lobes are enclosed in a fibrous capsule which dips into their substance dividing them into lobules that consist of an irregular branching framework of epithelial cells and lymphocytes. Function Lymphocytes originate from haemocytoblasts (stem cells) in red bone marrow. Those that enter the thymus mature and develop into activated T-lymphocytes i.e. able to respond to antigens encountered elsewhere in the body. They then divide into two groups : those that enter the blood, some of which remain in circulation and some lodge in other lymphoid tissue those that remain in the thymus gland and are the source of future generations of Tlymphocytes. The maturation of the thymus and other lymphoid tissue is stimulated by thymosin, a hormone secreted by the epithelial cells that form the framework of the thymus gland. Involution of the gland begins in adolescence and, with increasing age the effectiveness of T- lymphocyte response to antigens declines. Definition Return to top Antibodies are a type of protein. They are produced by the immune system in response to foreign substances that may be a threat to the body -- such as chemicals, virus particles, spores, or bacterial toxins. These foreign substances are called antigens. Each type of antibody is unique and defends the body against one specific type of antigen. Macrophages (Greek: "big eaters") are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. Macrophages are part of the innate immune system. Contents [hide] 1 Origin 2 Function o 2.1 Phagocytosis 3 Role in disease 4 Macrophage relatives [edit] Origin Macrophages are derived from monocytes. Monocytes grow in the bone marrow and enter the bloodstream. Circulating monocytes respond to chemical mediators of inflammation. Upon activation by these mediators, monocytes squeeze through the endothelium. Once through the endothelium, the monocytes are called macrophages. (Some monocytes differentiate into specialized cells such as dendritic cells or microglia). [edit] Function [edit] Phagocytosis Their main role is the removal of pathogens and necrotic debris. The latter function is more important in chronic inflammation. The early stages of inflammation are dominated by neutrophil granulocytes, which are ingested by macrophages if they come of age, see CD-31 for a description of this process.) Macrophages also present fragments of pathogens (called antigens) that they have ingested with MHC class II molecules on their cell membranes. Helper T cells recognize this and release a lymphokine notification to B cells. The B cells then create and release antibodies specific to the particular antigen, and hence to the pathogen. Macrophages again come into play because they are especially attracted to cells with antibodies attached. When a macrophage ingests a pathogen, the pathogen becomes trapped in a food vacuole, which then fuses with a lysosome. Within the lysosome, enzymes and toxic oxygen compounds digest the invader. However, some bacteria, such as Mycobacterium tuberculosis, have become resistant to these methods of digestion. A number of cell types are closely related to macrophages: Dendritic cells (including Langerhans cells) Microglia Kupffer cells Osteoclasts [edit] Role in disease Due to their role in phagocytosis, macrophages are involved in many diseases of the immune system. For example, they participate in the formation of granulomas, inflammatory lesions that may be caused by a large number of diseases. Some disorders, mostly rare, of ineffective phagocytosis and macrophage function have been described. Macrophages are the predominant cells involved in creating the progressive plaque lesions of atherosclerosis. When fighting influenza, macrophages are dispatched to the throat. However, until the killer T cells for the flu virus are found, the macrophages do more damage than help. They not only destroy throat cells infected with the flu virus, they destroy several surrounding non-infected cells. Macrophages also play a role in Human Immunodeficiency Virus (HIV) infection. Like T cells, macrophages can be infected with HIV but this does not kill macrophages, and instead they act as a reservoir of ongoing virus replication throughout the body. [edit] Macrophage relatives Tingible body macrophages are found the germinal centers of lymph nodes Microglia occur in the nervous system Kupffer cells are found in the liver Dendritic cells, such as Langerhans cells of the skin, are antigen-presenting cells of the immune system Blood - Blood plasma Pluripotential hemopoietic stem cell - Red blood cells (Reticulocyte, Normoblast) White blood cells Lymphocytes (Lymphoblast) T cells (Cytotoxic - Helper - Regulatory T cell) - B cells (Plasma cells & Memory B cells) Natural killer cell Myelocytes (Myeloblast) Granulocytes (Neutrophil, Eosinophil, Basophil) - Mast cell precursors - Monocytes (Histiocyte, Macrophages, Dendritic cells, Langerhans cells, Microglia, Kupffer cells) Megakaryoblast - Megakaryocyte - Platelets Retrieved from "http://en.wikipedia.org/wiki/Macrophage" Category: Macrophages gamma globulin GAMMA GLOBULIN [gamma globulin] a group of globulin proteins in human blood plasma, including most antibodies . These antibody substances are produced as a protective reaction of the body's immune system to the invasion of disease-producing organisms (see immunity ). Injections of gamma globulin are used to create a rapid but temporary immunity in patients who have been exposed to certain diseases. Children who have been exposed to, but are not immunized against, measles and patients with hepatitis receive some protection from gamma globulin when it is administered during the incubation period of the infection. The gamma globulin used for such purposes is extracted from blood plasma from a large, diverse adult population; the resulting mixture is thus likely to contain antibodies from individuals who had been exposed to the appropriate infections.