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If immune complex persists or become trapped in tissues Type III hypersensitivity:.Neutrophils clear only large complexes.Monocytes and macrophages remove large complexes, but don't clear complexes with excess Ag very well.Sometimes Ag-Ab complex comes out of solution.IgM much bigger, with multiple binding sites compared to IgG) Large complex formation determined by:.Size and form of immune complex depends on how much Ag and Ab are involved.Type III (Immune complex) hypersensitivity.salmonella or Mycobacterial infections – endotoxins coat patient's cells, cells destroyed by antibodies. Sedormid is a drug that adsorbs on to platelets.
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Thyroid cells (Hashimoto's thyroiditis), kidney cells (Goodpasture's Syndrome), muscle cells (Myesthemia gravis).Examples: incompatible blood transfusion, rhesus-incompatibility, Ab against self-molecules, e.g.:.Cells involved: neutrophils, eosinophils, monocytes and NK cells.In Type II hypersensitivity, antibodies bind to cells or to an antigen adsorbed onto host cells.ADCC: Antibody-dependant cell-mediated cytotoxicity.Definition: production of Ab against a self-molecule or against a foreign Ag bound to a cell surface, an infectious agent or inert material damaging reactions (inappropriate host response).The higher individual's IgE level, the greater chances of allergy – strong family association.
#TYPE 3 HYPERSENSITIVITY EXAMPLES SKIN#
If allergen in intestinal mucosa eg nuts, strawberries and fish, a mixed reaction occurs including skin rashes and asthma.local reaction occurs in respiratory areas. If allergen enters mucous eg pollen, house dust etc.Insect venom systemic anaphylaxis with dyspnoea, bronchospasm, laryngeal edema and vasodilation sudden drop in BP. If the allergen is injected into circulation (i.e.If out of control anaphylactic response. Histamine causes: smooth muscle contraction, vasodilation, increased vascular permeability.Mast cells and basophils release histamine and other factors (heparin, chemotactic factors, platelet activating factors).This is the case with allergic patients due to very high levels of IgE. IgE molecules must be close to one another in order for a response to be generated to antigenic binding. Note that several IgE's are anchored on surfaces of mast cells and basophils.Also low levels of many different epitopes (idiotypes), but large amount of sites to a particular epitope.Many epitopes (antigenic determinants) expressed on cell surfaces in low amounts.These cells have surface receptors for the Fc region of the IgE molecule.IgE associates with two cell types: basophils and mast cells.Very high levels of IgE produced by plasma cells.Second response: IgG produced by plasma cells.The exact mechanism that leads B cells to produce IgE is not known Mechanisms:.Levels of circulating IgE to an allergen determine whether an anaphylactic reaction will occur upon re-exposure to the same Ag.Atopy: asthma, eczema, hay fever, food allergy, urticaria (hives).The antigen is classified as an allergen.Types I, II, III are antibody mediated.Causes inflammatory response and tissue damage.Definition: Exaggerated or inappropriate response of body's immune system.Type I, II, and III reactions are the result of antibody actions, while type IV reactions involve T cell lymphocytes and cell-mediated immune responses. Hypersensitivity reactions are categorized into four major types: type I, type II, type III, and type IV. Tuberculin reactions, chronic asthma, and contact dermatitis are examples of type IV reactions. Type IV hypersensitivities are regulated by T cells and are delayed reactions to antigens associated with cells.Serum sickness and rheumatoid arthritis are examples of type III reactions.
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In an attempt to remove these complexes, underlying tissue is also damaged.