kidney 1 kidney 2 Allergy and Hypersensitivity Dr

kidney 1

kidney 2

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 Ig. E mediate reactions.

Classification • Antibody mediated hypersensitivity Type I ------- Ig. E Type II ------- Ig. G Type III -------Ig. G • 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 Ig. E 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 Ig. E 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 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