[W10] PGK hypersensitivity Flashcards
(18 cards)
What is hypersensitivity?
An inappropriate or exaggerated immune response to harmless antigens.
What are the four types of hypersensitivity reactions?
Type I – IgE
Type II – IgG/IgM
Type III – Immune complexes
Type IV – T cell-mediated
What triggers a type I hypersensitivity reaction?
Allergen cross-linking IgE on mast cells/basophils.
What do mast cell granules contain?
Histamine, serotonin, prostaglandins, chemotactic factors.
What is systemic anaphylaxis?
A life-threatening allergic reaction involving airway obstruction and circulatory shock.
How is systemic anaphylaxis treated?
Adrenaline injection (EpiPen).
What mediates type II hypersensitivity?
IgG or IgM antibodies targeting cell surfaces.
What are two outcomes of type II reactions?
Complement lysis
ADCC
What is haemolytic disease of the newborn?
Rh⁻ mother makes anti-Rh antibodies that attack Rh⁺ fetal RBCs in later pregnancy.
How is haemolytic disease of the newborn prevented?
RHOGAM (anti-Rh IgG) given after first Rh⁺ birth.
What causes type III hypersensitivity?
Deposition of antigen–antibody complexes in tissues.
What is serum sickness?
A systemic reaction to injected foreign serum proteins.
What is Farmer’s lung?
Type III reaction from mold antigens in hay.
What is an Arthus reaction?
A localized type III response with swelling and redness after antigen injection.
What mediates type IV hypersensitivity?
T helper 1 (TH1) cells and macrophages.
How long does it take for a type IV response to occur?
24–72 hours after exposure.
What is a common feature of chronic type IV reactions?
Granuloma formation (e.g. in TB).
Name 3 examples of type IV hypersensitivity.
Tuberculosis
Poison ivy
Nickel contact dermatitis
