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hypersensitivity |
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hypersensitivity /hy·per·sen·si·tiv·i·ty/ (-sen″sĭ-tiv´ĭ-te) a state of altered reactivity in which the body reacts with an exaggerated immune response to what is perceived as a foreign substance. The hypersensitivity states and resulting reactions are usually subclassified by the Gell and Coombs classification (q.v.).hypersen´sitive antibody-mediated hypersensitivity 1. type II h.; see Gell and Coombs classification, under classification. 2. occasionally, any form of hypersensitivity in which antibodies, rather than T lymphocytes, are the primary mediators, i.e., types I–III. cell-mediated hypersensitivity type IV h.; see Gell and Coombs classification, under classification. contact hypersensitivity a type IV hypersensitivity produced by contact of the skin with a chemical substance having the properties of an antigen or hapten. cytotoxic hypersensitivity type II h.; see Gell and Coombs classification, under classification. delayed hypersensitivity (DH), delayed-type hypersensitivity (DTH) that which takes 24 to 72 hours to develop and is mediated by T lymphocytes rather than by antibodies; usually used to denote the subset of type IV hypersensitivity involving cytokine release and macrophage activation, as opposed to direct cytolysis, but sometimes used more broadly, even as a synonym of type IV h. immediate hypersensitivity 1. type I h.; see Gell and Coombs classification, under classification. 2. occasionally, any form of hypersensitivity mediated by antibodies and developing rapidly, generally in minutes to hours (i.e., types I–III ), as distinguished from that mediated by T lymphocytes and macrophages and requiring days to develop (type IV, or delayed h. ). immune complex–mediated hypersensitivity type III h.; see Gell and Coombs classification, under classification. T cell–mediated hypersensitivity type IV h.; see Gell and Coombs classification, under classification. type I hypersensitivity see Gell and Coombs classification, under classification. type II hypersensitivity see Gell and Coombs classification, under classification. type III hypersensitivity see Gell and Coombs classification, under classification. type IV hypersensitivity see Gell and Coombs classification, under classification.
Hypersensitivity After the body's immune system attacks an outside invader (such as organic dust or a fungus) many times, exposure to even a tiny amount of this allergen can provoke a strong inflammatory response. Mentioned in: Allergic Bronchopulmonary Aspergillosis, Asthma, Detoxification, Hypersensitivity Pneumonitis
hypersensitivity [-sen′sətiv′itē] Etymology: Gk, hyper + L, sentire, to feel an abnormal condition characterized by an exaggerated response of the immune system to an antigen. See also allergy. hypersensitive, adj. hypersensitivity, n 1. an adverse reaction to contact with specific substances in quantities that usually produce no reaction in normal individuals. n 2. an allergic tendency. In general, a tendency to react with unusual violence to stimuli. n 3. a common complaint after periodontal therapy in which dentin may be exposed, resulting in pain in the teeth or sensitivity to heat, cold, and sweet substances. hypersensitivity, atopic, n See atopy. hypersensitivity, bacterial, n delayed inflammatory reaction resulting from previous sensitization of the host by an antigen. hypersensitivity, delayed, n a type involving a latent period between the antigen introduction and the reaction; cellular reactions mediated by the T lymphocytes (e.g., tuberculosis, and transplant reaction). hypersensitivity, dentin, n refers to the pain caused by fractures, or gingival recession, which exposes the dentin of a tooth. This condition requires immediate treatment and can be corrected with topical agents or with periodontal or restorative procedures, such as gingival grafts or enamel bonding. hypersensitivity, immediate, n a humoral reaction, mediated by the circulating B lymphocytes, which causes any of three immediate responses: anaphylactic hypersensitivity, cytotoxic hypersensitivity, and immune system hypersensitivity. hypersensitivity reaction, cytotoxic, n a reaction in which the surface antigens of a cell join with an antibody, causing complement-mediated cell destruction, or other types of cell-membrane damage. hypersensitivity reactions, immune complex,
n.pl one of four types of hypersensitivity reactions to antigens in the body that acts as a barrier to disease. The reactions can cause tissue damage. hypersensitivity 1. a state of altered reactivity in which the body reacts with an exaggerated immune response to a foreign agent; allergy is a synonym for hypersensitivity. anaphylaxis is a form of hypersensitivity. There are four basic types of hypersensitivity reactions: Type I (called also immediate hypersensitivity) involves cell-fixed antibody, mainly IgE attached to mast cells or basophils. Antigen binding causes the cell to release vasoactive factors. The basis for anaphylaxis and atopy. Type II causes cell destruction (cytotoxicity) by the action of immunoglobulin with complement or cytotoxic cells. Seen in red blood cell transfusion reactions and in alloimmune hemolytic anemia. See also antibody-dependent cellular cytotoxicity. Type III (called also immune-complex or subacute hypersensitivity) causes tissue damage and inflammation by the deposition of antigen-antibody complexes that activate complement and attract polymorphonuclear cells. Type IV (called also delayed hypersensitivity) involves sensitized T lymphocytes that react with cell bound or associated antigen and release lymphokines, causing mononuclear cell accumulation, tissue damage and inflammation, typically manifesting at least 24 hours after exposure to the antigen. 2. a state of increased responsivity to physical stimuli. hypersensitivity angiitis variant of polyarteritis nodosa; a disease of small blood vessels in humans; called also leukocytoclastic vasculitis. antibody-mediated hypersensitivity types I, II and III hypersensitivity reactions. Called also immediate hypersensitivity. bacterial hypersensitivity immune responses to bacteria or bacterial products may contribute to the clinical features of some diseases, e.g. the anemia associated with salmonellosis, arthritis in erysipelas of pigs, intestinal lesions in Johne's disease, or be the principal cause as in staphylococcal hypersensitivity dermatitis in dogs. contact hypersensitivity a type IV reaction produced by contact of the skin with a low-molecular-weight chemical substance having the properties of a hapten in a sensitized individual; it includes allergic contact dermatitis. cutaneous basophil hypersensitivity a delayed inflammatory response characterized by large numbers of basophils. cytotoxic hypersensitivity type II hypersensitivity. delayed hypersensitivity type IV reaction. A slowly developing cell-mediated immune response in which T helper 1 lymphocytes respond to specific antigen by releasing cytokines, some of which activate macrophages, as occurs in tuberculin reaction, graft rejection, some autoimmune diseases, etc. drug hypersensitivity may be either an immediate (antibody mediated) or delayed type (T lymphocyte mediated) reaction. See also drug eruption. flea bite hypersensitivity see flea allergy dermatitis. food hypersensitivity hypersensitivity reaction to various dietary constituents has been the suspected cause of allergic dermatitis in most species, but conclusive evidence is often lacking. It may also result in diarrhea. fungal hypersensitivity may contribute to the clinical features of cutaneous fungal infections, particularly kerion formation. It is also the basis for skin testing for systemic mycoses, e.g. histoplasmin and coccidioidin. helminth hypersensitivity occurs, e.g. the self-cure phenomenon, and the allergic response of a sensitized animal to an invasion, e.g. of lungs, causes massive pulmonary edema. immediate hypersensitivity antibody-mediated hypersensitivity, i.e. types I, II and III, characterized by a response that appears within minutes to hours, resulting either from a release of histamine and other mediators of hypersensitivity from IgE-sensitized mast cells, causing increased vascular permeability, edema and smooth muscle contraction (type I), from antibody-mediated lysis of red blood cells (type II), or from immune complex mediated pathology (type III). immune complex hypersensitivity type III hypersensitivity (above). mold hypersensitivity see acute bovine pulmonary emphysema-edema. hypersensitivity pneumonitis see hypersensitivity pneumonitis. staphylococcal hypersensitivity see bacterial hypersensitivity (above). hypersensitivity threshold a theory that certain levels of allergens may be tolerated by some sensitized individuals without manifestations of disease, but a slight increase in the level precipitates clinical signs. tuberculin type hypersensitivity
the classical T lymphocyte cell-mediated hypersensitivity associated with mycobacterium infection or immunization with antigens containing Freund's adjuvant. hypersensitivity
An excessive reaction, local or systemic, or inappropriate immune response to an antigen. Four types of immune responses are usually described, but the main reaction involving the eyes is type 1. They are also called allergic reactions types 1-4.
type 1 hypersensitivity An immediate, abnormal reaction occurring when an antigen reacts with an antibody (e.g. immunoglobulin E (IgE)) attached to a mast cell or basophil. This leads to the release of specific chemical mediators of allergy (e.g. histamine) that react with target organs throughout the body. Systemic signs include: itching, lacrimation, skin rash and possibly haemodynamic collapse and shock. Allergic conjunctivitis is an example of this type of hypersensitivity. Type 2 h . (cytotoxic h.) is caused by an interaction of antibody and antigens on cell surfaces. Examples: Graves' disease, myasthenia gravis. Type 3 h. (immune-complex mediated h.) is mediated by a combination of antigen-antibody. Example: systemic lupus erythematosus. Type 4 h. (T cell-mediated h.) is a delayed reaction (several days to develop) mediated by T lymphocytes. Example: rheumatoid arthritis. See antihistamine; mast cell stabilizers. hypersensitivity Immunology An abnormal immune response that may be immediate–due to antibodies of the IgE class, or delayed–due to cell-mediated immunity. See Cold hypersensitivity, Immediate hypersensitivity Neurology
Exaggerated sensitivity An ↑in a person's sensitivity to light, sound, smell, taste, touch, temperature, balance, and even emotional issues, which may be linked to anxiety and panic disorders. Patient discussion about cutaneous basophil hypersensitivity. Q. what is the most common allergy? is it dust allergy? A. thanks, I've heard of a new allergy treatment and trying to learn some more about the different kinds... Q. What is Gluten and what is gluten allergy? My nephew is coming to stay with me for a few days and his mother told me that since he is allergic to gluten that I shouldn't give him to eat any. What is gluten? A. Gluten is a protein that is found in wheat (and similar proteins of the tribe Triticeae which includes other cultivars such as barley and rye). When someone is allergic to gluten the only effective treatment is a lifelong gluten-free diet. Here is a link to a website with ideas for cooking without gluten: http://www.celiac.com/categories/Gluten%252dFree-Cooking/ Q. What happens when you get an allergy test? My doctor told me that I should have an allergy test done. I have had a friend have an allergy test done and she had a bunch of bumps on her arm. My doctor said it was just a simple blood test. Has the test changed? What should I expect? Is it painful? A. Today, you can check allergy also with a blood test. What you check is the antibodies that your body manufactures. They extract antibodies from the blood and react it to all sort of allergens and see what happens. Here is a more elaborated explanation about it : Read more or ask a question about cutaneous basophil hypersensitivityhttp://www.labtestsonline.org/understanding/analytes/allergy/sample.html How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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