Four Types of Hypersensitivity Reactions: A Comprehensive Guide for Managing Allergic Reactions in Clinical Practice

What are the different types of hypersensitivities?

– Type 1: anaphylactic reactions – Type 2: cytotoxic reactions – Type 3: immune complex reactions – Type 4: cell-mediated reactions

Hypersensitivity reactions, also known as allergic reactions, are excessive responses of the immune system towards certain allergens that are harmless to most individuals. There are four major types of hypersensitivity reactions, namely:

1. Type I Hypersensitivity: This type of hypersensitivity, also known as immediate hypersensitivity, occurs rapidly within minutes of exposure to an allergen. It involves an IgE-mediated immune response that results in the release of various chemicals like histamine, leukotrienes, prostaglandins, and cytokines from mast cells and basophils. Examples of Type I hypersensitivity include allergic rhinitis, anaphylaxis, asthma, and food allergies.

2. Type II Hypersensitivity: Also known as cytotoxic hypersensitivity, Type II hypersensitivity occurs when antibodies, particularly IgM and IgG, bind to antigens present on the surface of cells or tissues, leading to tissue damage and inflammation. Examples of Type II hypersensitivity include hemolytic transfusion reactions, autoimmune hemolytic anemia, and Goodpasture’s syndrome.

3. Type III Hypersensitivity: Type III hypersensitivity, also called immune complex-mediated hypersensitivity, occurs when antigens and antibodies form immune complexes that deposit on tissue surfaces, leading to inflammation and tissue damage. Examples include systemic lupus erythematosus, rheumatoid arthritis, and serum sickness.

4. Type IV Hypersensitivity: Type IV hypersensitivity, also called delayed-type hypersensitivity, involves the activation of T-cells and macrophages by antigens, leading to inflammation and tissue damage. Examples of Type IV hypersensitivity include contact dermatitis, tuberculin skin test reactions, and transplant rejection.

It’s important to know the different types of hypersensitivity reactions to better understand and manage allergic reactions in clinical practice.

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