Hypersensitivity

Definition

Hypersensitivity is an exaggerated immune response to an antigen, causing damage to the host. It can be classified into four types: Type I (immediate), Type II (cytotoxic), Type III (immune complex-mediated), and Type IV (delayed-type).

5 Must Know Facts For Your Next Test

1. Type I hypersensitivity involves IgE antibodies and is commonly associated with allergies.
2. Type II hypersensitivity is mediated by IgG or IgM antibodies targeting cell surface or matrix antigens, leading to cell destruction.
3. Type III hypersensitivity occurs when immune complexes deposit in tissues, causing inflammation and tissue damage.
4. Type IV hypersensitivity is a T-cell mediated response that typically takes 48-72 hours to develop.
5. Common examples of hypersensitivity reactions include allergic rhinitis, hemolytic anemia, serum sickness, and contact dermatitis.

Review Questions

• What type of antibody is involved in Type I hypersensitivity?
• Which type of hypersensitivity reaction involves T-cells?
• Give an example of a clinical condition associated with Type III hypersensitivity.

Related terms

Allergen: A substance that can cause an allergic reaction.

Autoimmunity: A condition in which the immune system attacks the body's own tissues.

Anaphylaxis:

A severe, potentially life-threatening allergic reaction.