The Great Precipitator

Clinical Immunology: Hypersensitivity, Allergy, and Autoimmune Diseases

Course Details

• Class: Foundation Year Course Introduction to Human Disease

• Course Code: IHD 3

• Lecturer: Olga Piskareva

• Date: 2026

Learning Outcomes

• ALO 1: Explain the three main mechanisms of antibody action:

  • direct action

  • activation of the complement system

  • activation of the anaphylactic system

• ALO 2: Define allergy and compare allergic rhinitis with anaphylaxis

• ALO 3: Describe clinical diagnostic uses of antibodies and the ELISA test.

Introduction to Immunology: Innate Immune System

• Antibodies do not directly destroy antigens; instead, they label antigens for destruction through the following pathways:

  • Direct Action: Agglutination, precipitation, neutralization

  • Activation of the Complement System

  • Activation of the Anaphylactic System

Antibody Action: Direct Action

• Antibody action involves three main processes:

  1. Agglutination: Clumping together of antigenic agents to form an antibody-antigen complex.

  2. Precipitation: A soluble antigen becomes insoluble and precipitates out of solution.

  3. Neutralization: Antibodies bind to specific sites on bacterial exotoxins or viral surface antigens, inhibiting their action or entry into cells.

Immunoglobulin Classes

• **IgM (