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match them as closely as possible to decrease the risk of rejection. Class I antigens are HLA-A, HLA-B, HLA-C & are found in most human cells. They are primarily responsible for organ rejection. Class II antigens are found on macrophages, dendritic cells, Langerhans cells, B cells & T cells. Some diseases such as ankylosing spondylitis are associated with the presence of a specific HLA antigen. Persons with HLA-B27 are at an increased risk of developing ankylosing spondylitis.Human leukocyte antigen (HLA): Immune response against antigens on donated tissue. Type IV cell mediated reaction (rejection within 2 weeks w/o immunosuppressive drugs**Matching HLA-DR locus appears to be most critical for graft acceptance**
EXTRA INFO ABOUT ALLERGIC REACTION, MAY NOT NEED MOST OF ITHypersensitivityEtiologyClinical ManifestationsPathophysiology Type I(HypersensitivityResponse)It is an immediate hypersensitivity response to an environmental allergen. Most of the reactions are attributed to allergies to food, medication, pollen, etc. The reaction occurs in minutes to hours from the time of the exposure to the allergen.Environmental allergies: asthma, asthma exacerbation, food, drug, animal, & insect venom allergies.Angioedema: which may be idiopathic or related to medications, causing swelling of the lips, eyes & larynx. (Anaphylaxis).Atopic Disorders: type I reaction & include hay fever, asthma, eczema, & urticaria. They have strong genetic disposition.Pathogenesis begins with the antibody IgE. Upon initial exposure to the allergen IgE binds with the allergen. This primes the stage for a reaction to later occur. Upon re-exposure, the allergen (antigen) binds with the previously formed antigen-IgE complex. The mast cell detects the complex & begins to degranulates. It releases histamine & triggers the inflammatory cascade. Clinical manifestations are dependent on the route the allergen entered the body.Type II(Antibody mediated or Cytotoxic Hypersensitivity)It is a reaction which is mediated by antibodies directed against fixed antigens on the plasma membranes of the cells. This is an IgG & IgM antibody mediated reaction.Alloimmune reactions: to blood transfusions result from the wrong blood type being administered. ABO incompatibility is a good example.. **Organ Transplant reactions***Rh incompatibility:is another example of a type II reaction. A person who is Rh + has the Rh antigen. If they are negative, they do not have the antigen & are Rh-. Giving blood that is Rh- to a patient that is Rh+ will cause a transfusion reaction.Autoimmune Examples: Graves’ dz is a type of hyperthyroidism. In this disorder autoantibodies are formed against thyroid cells. They bind to thyroid cells & mimic the action of TSH. The pathogenesis begins with the binding of IgG & IgM to an antigen on a plasma membrane. This activates complement & it forms the membrane attackcomplex (MAC) which causes cell lysis. IgG & C3b may also bind to the antigen & the macrophages & trigger cell lysis through phagocytosis. Both IgG & complement attract neutrophils to the tissues.