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Line 1: − {{toplink+ − |linkpage =WikiClinical − |linktext =WIKICLINICAL − |sublink1 = Immunology - WikiBlood − |subtext1 = IMMUNOLOGY − }} − <br> − − ==Introduction== − − '''Autoimmune disease''' is defined as ''a disease state characterized by a specific antibody or cell mediated response against the body's own tissues ('self' antigens). − − The breakdown of [[Immune Tolerance - WikiBlood|tolerance]] to self antigens and the failure to regulate pathological immune responses are both responsible for autoimmune diseases. It has been shown in mice that thymectomy causes autoimmune disease, and plays a very important role in the recognition of 'self'. − − Particular individuals may be more susceptible to autoimmune diseases due to: − − ===Genetic factors=== − − Many autoimmune diseases have a familiar component and the Human Leucocyte Antigen (HLA) haplotype is the prodomient genetic factor, however having a particular HLA haplotype does not automatically result in the development of an autoimmune disease. − − * HLA-DR3/DR4 (MHC Class II): − 1. Diabetes Mellitus − − 2. Rheumatoid Arthritis − − * HLA-B27 (MHC Class I): − 1. Ankylosing spondylitis − − * TNF alpha − − * CTLA-4 − − ===Hormonal factors=== − − Testosterone is protective against Systemic Lupus Erythematosus (SLE) and thus it is not seen in males. − − ===Environmental factors=== − − '''''Infection''''' − − 1. Molecular mimicry − − * Some bacteria and viruses have antigens that resemble host-cell components and the body then also can initiate an immune response against itself. − − 2. Polyclonal activation − − * T and B cells activation can occur as a result of an infection resulting in polyclonal activation. This can then cause autoreactive autoantibodys or mediate autoimmunity. − − 3. Inappropriatee MHC expression − − * Autoreactive T cells are activated because infection stimulates APC and upregulates MHC class II. − − '''''Diet''''' − − '''''Stress''''' − − − − {| border="1" cellpadding="2" − !width="150"| − !width="150"|Antibody mediated − !width="50"|Antibody mediated − !width="200"|Cell mediated − |- − | '''Type of hypersensitivity''' || [[Type II Hypersensitivity - WikiBlood|Type II]] || [[Type III Hypersensitivity - WikiBlood|Type III]] || [[Type IV Hypersensitivity - WikiBlood|Type IV]] − |- − | '''Pathogenesis''' || Antibody to cell surface or matrix antigens || Antibody to soluble self antigens || T cell and macrophage activation to self antigens − |- − | '''Examples of diseases''' || Immune mediated haemolytic anaemia (IMHA) || Systemic Lupus Erythematosus (SLE) || Rheumatoid arthritis − |- − | || Immune mediated thrombocytopaenia (IMTP)|| || Diabetes Mellitus type 1 − |- − | || Myasthenia gravis || || Hypothyroidism (lymphocytic throiditis) − |- − | || Pemphigus Vulgaris || || Hypoadrenocorticism (Addisons disease) − |- − | || Bullous pemphigoid || || − |} − − ==Antibody mediated autoimmune diseases== − [[Image:Large.jpg|right|thumb|150px|Myasthenia gravis - From Immunity: The Immune Response in Infectious and Inflammatory Disease DeFranco, Locksley and Robertson New Science Press 1999-2007]] − − ===1. Immune Mediated Haemolytic Anaemia (IMHA)=== − − '''Pathogenesis:''' [[Type II Hypersensitivity - WikiBlood|Type II hypersensitivity]] − − * Autoantibody attack on the red blood cells causing extravascular and intravascular lysis which causes anaemia. − * The in saline autoagglutination test and the coombes test is used to diagnose the disorder. − − ===2. Immune Mediated Thrombocytopaenia (IMTP) === − − '''Pathogenesis:''' [[Type II Hypersensitivity - WikiBlood|Type II hypersensitivity]] − − * There is an immunological attack on the platelets which reduces the ability for clotting. − * A reduced platelet count and detection of anti-platelet antibodies in the serum are used for diagnosis of this disorder. − − ===3. Myasthenia gravis=== − − '''Pathogenesis:''' [[Type II Hypersensitivity - WikiBlood|Type II hypersensitivity]] − − ===4. Bullous Pemphigoid=== − − '''Pathogenesis:''' [[Type II Hypersensitivity - WikiBlood|Type II hypersensitivity]] − − ===5. Pemphigus Vulgaris=== − − '''Pathogenesis:''' [[Type II Hypersensitivity - WikiBlood|Type II hypersensitivity]] − − ===6. Systemic Lupus Erythematosus (SLE)/Multi-systemic immune mediated disease=== − − '''Pathogenesis:''' [[Type III Hypersensitivity - WikiBlood|Type III hypersensitivity]] − − ==Cell mediated autoimmune diseases== − [[Image:Rheumatoid Arthritis Type IV hypersensitivity.jpg|right|thumb|150px|Rheumatoid Arthritis-Brian Catchpole RVC 2008]] − [[Image:Diabetes Mellitus Type IV hypersensitivity.jpg|right|thumb|150px|Diabetes Mellitus-Brian Catchpole RVC 2008]] − − ===1. Rheumatoid arthritis=== − − '''Pathogenesis:''' − − * [[Type IV Hypersensitivity - WikiBlood|Type IV hypersensitivity]]: CD4 Th-1 cell mediated. − * Macrophages phagocytose self antigens and can present peptides on their MHC Class II molecules. The autoreactive TH-1 cells release IFN-gamma which activates macrophages to release prostaglandins, MMP enzymes and TNF-alpha (pro-inflammatory mediator), see diagram. These cytokines cause inflammation and tissue destruction. − − ===2. Diabetes Mellitus type I=== − '''Pathogenesis:''' − − * [[Type IV Hypersensitivity - WikiBlood|Type IV hypersensitivity]] − * The CTLs think that all the beta cells in the pancreas are infected by a virus, as it wrongly detects a self antigen presented by the MHC class I on the surface of the cell as foreign. − * Autoreactive CD8+ CTLs are inadvertently activated destroying the beta cells thus preventing the secretion of insulin and causing diabetes type 1 (see diagram). − − ===3. Hypothyroidism (lymphocytic throiditis)=== − − '''Pathogenesis:''' [[Type IV Hypersensitivity - WikiBlood|Type IV hypersensitivity]] − − * T cell mediated − − ===4. Hypoadrenocorticism (Addisons disease)=== − − '''Pathogenesis:''' [[Type IV Hypersensitivity - WikiBlood|Type IV hypersensitivity]] − − ==References==
moved Autoimmune diseases - WikiClinical to Autoimmune Diseases
#REDIRECT[[:Category:Autoimmune Diseases]]