Mechanisms of Hypersensitivity Reactions

Clinical Manifestations and Diagnostic Methods

Hypersensitivity reactions are exaggerated immune responses to antigens, leading to tissue damage. These reactions are categorized into four types: Type I (Immediate), Type II (Cytotoxic), Type III (Immune Complex), and Type IV (Delayed-Type).

Types of Hypersensitivity Reactions

• Type I: Mediated by IgE antibodies, leading to anaphylaxis and allergic diseases.
• Type II: Antibody-dependent cytotoxicity targeting cell surface antigens.
• Type III: Immune complex deposition causing inflammation.
• Type IV: T-cell-mediated delayed response, observed in conditions such as tuberculosis.

Clinical Manifestations

Common symptoms include respiratory distress, dermatologic reactions, and systemic inflammatory responses.

Diagnostic Methods

• Skin tests: Used for Type I hypersensitivity assessment.
• Serological assays: Detect circulating antibodies in Type II and III reactions.
• Patch tests: Help identify delayed hypersensitivity responses.

Understanding these mechanisms is crucial for diagnosis and treatment of hypersensitivity-related conditions.