Hypersensitivity

Question 1

Type 1

Answer 1

1. Anaphylactic (Type I) Hypersensitivity:

Description:
-Most severe hypersensitivity reaction, characterized by rapid-onset anaphylaxis.
Clinical Features:
-Edema in various tissues, including the larynx.
-Accompanied by hypotension, bronchospasm, and cardiovascular collapse in severe cases.
Onset: Immediate, within minutes of exposure to an antigen.
Mediators: Primary chemical mediators responsible for symptoms.
Duration: Delayed reaction may occur, lasting up to 24 hours.

Question 2

Type 2

Answer 2

Cytotoxic (Type II) Hypersensitivity:

Description: Antibodies target antigens on cells or basement membranes, leading to cell lysis and tissue damage.
Example: Hemolytic transfusion reaction where anti-B antibodies attack transfused type B blood cells.

Question 3

Type 3

Answer 3

Immune Complex (Type III) Hypersensitivity:

Description: Damaging inflammatory reaction caused by insoluble immune complexes formed by antigens binding to antibodies.
Outcome: Immune complexes deposited in tissues or vascular endothelium, triggering inflammation.
Examples: Rheumatoid arthritis, autoimmune disorders like systemic lupus erythematosus.

Question 4

Stage 4

Answer 4

Delayed (Type IV) Hypersensitivity:

Description: T cell–mediated immune reaction occurring 24 to 48 hours after exposure to an antigen.
Example: Reaction to subcutaneous injection of purified protein derivative (PPD) antigen from Mycobacterium tuberculosis.
Manifestation: Erythema and induration due to sensitized T cells.