Introduction to Hypersensitivity types of hypersensitivity mechanisms ,diagnosis,tests and treatment.pptx

Hypersensitivity

1. Introduction to Hypersensitivity Hypersensitivity refers to an overreaction of the immune system to foreign substances, leading to harmful symptoms. Understanding the different types and mechanisms of hypersensitivity is crucial for managing and treating these reactions effectively. by samia abdalrhman

2. Types of Hypersensitivity Reactions Type I Immediate (IgE-mediated) hypersensitivity, such as allergic reactions. Type II Antibody-mediated cytotoxic hypersensitivity, where antibodies bind to cell surface antigens. Type III Immune complex-mediated hypersensitivity, caused by the deposition of antigen-antibody complexes.

3. Immediate Hypersensitivity (Type I) 1 Allergens Exposure to harmless substances like pollen, dust, or food triggers the release of IgE antibodies. 2 Mast Cell Activation IgE binds to mast cells, causing them to release histamine and other inflammatory mediators. 3 Symptoms Symptoms include sneezing, itching, swelling, and potentially life-threatening anaphylaxis.

4. Antibody-Mediated Hypersensitivity (Type II) Target Antigens Antibodies bind to specific cell surface antigens, leading to cell destruction. Complement Activation Antibody binding can activate the complement system, further damaging target cells. Examples Autoimmune diseases like autoimmune hemolytic anemia and Goodpasture's syndrome.

5. Immune Complex-Mediated Hypersensitivity (Type III) 1 Antigen-Antibody Complexes Soluble antigen-antibody complexes form when there is an excess of antigen. 2 Deposition The complexes deposit in blood vessel walls and other tissues, triggering inflammation. 3 Tissue Damage Activated complement and phagocytes cause damage to the affected tissues.

6. Cell-Mediated Hypersensitivity (Type IV) 1 Sensitized T Cells T cells become sensitized to a specific antigen after initial exposure. 2 Antigen Encounter Upon re-exposure, the sensitized T cells mount a delayed inflammatory response. 3 Tissue Damage The inflammatory response can lead to tissue damage and granuloma formation.

7. Immune System and Hypersensitivity Antigen Exposure The immune system recognizes foreign substances as antigens, leading to sensitization. Antibody Production B cells produce antibodies that bind to specific antigens, triggering hypersensitivity. T Cell Activation T cells play a central role in cell-mediated hypersensitivity reactions.

8. Strategies for Managing Hypersensitivity Avoidance Identifying and avoiding the trigger antigen is the primary strategy for managing hypersensitivity. Medication Anti-histamines, corticosteroids, and other drugs can help manage the symptoms of hypersensitivity. Immunotherapy Gradual exposure to the allergen can help desensitize the immune system over time.

9. Mechanism of Hypersensitivity Allergen Exposure The immune system encounters a foreign antigen or allergen. Sensitization The immune system becomes primed to recognize the antigen. Hypersensitivity Reaction Upon re-exposure, the immune system mounts an exaggerated response, leading to symptoms.