kidney

kidney

Allergy and Hypersensitivity Dr Farzana Salman

Allergy and Hypersensitivity Hypersensitivity is the term used when an immune response results in exaggerated or inappropriate reactions harmful to the host. Allergy is often equated with hypersensitivity but should be limited to the IgE mediate reactions.

Classification Antibody mediated hypersensitivity Type I ------- IgE Type II ------- IgG Type III -------IgG Cell mediated hypersensitivity Type IV----- T lymphocytes

Classification Immediate hypersensitivity----- B Lymphocytes Delayed hypersensitivity-------- T Lymphocytes

Type I---Atopic Allergy

Antigen induces the formation of IgE antibody (Reagins or sensitized antibodies) Binds firmly to the surface of mast cells and basophils. Reexposure to the same antigen results in cross linking to the cell bound IgE antibody. Degrannulation Release of pharmacologically active mediators within minutes. ( Calcium mediated release)

Histamine Protease Slow reacting substance of anaphylaxis Eosinophil chemotactic substance Neutrophil chemotactic substance Heparin Platelet activating factors

Dilatation of local blood vessels Attraction of eosinophils and neutrophils to the reactive site. Increased permeability of the capillaries with loss of fluid in the tissues. Contraction of local smooth muscle.

Symptoms Compliment system is not activated. Edema Erythema Itching Compliment system is not activated. Genetically passed from parent to child.

Clinical Manifestations Anaphylaxis Allergen is injected directly into circulation. causes – peanuts,shell fish ,bee venom ,penicillin Urticaria Allergen enters specific regions of the skin Hives--- Localized swellings Hay fever Allergen reagin reaction occurs in the nose Asthma Allergen reagin reaction occurs in the bronchioles of the lungs

Type II--- Cytotoxic Hypersensitivity Occurs when antibody directed at antigens of the cell membrane activates compliment complex. Membrane attack complex . Compliment mediated lysis Phagocytes are attracted towards the site. Drugs Infections Blood transfusion reactions

Type III--- Immune complex Hypersensitivity Antigen antibody complexes induce an inflammatory response in the tissues. Reticuloendothelial system Persist and are deposited in tissues Persistent microbial or viral infections Joints (arthritis) Kidneys (nephritis) Blood vessels (vasculitis)

Type IV– Delayed Reaction Allergy Activated T cells Poison Ivy Contact dermatitis Graft rejection