10: Hypersensitivity Flashcards
Type I
allergy and anaphylaxis
Type II
antibody-mediated cytotoxicity
Type III
immune complex disease
Type IV
delayed-type hypersensitivity
type I, II, III = antibody mediated
type IV = cell-mediated
Type I method
antigen binding to surface of IgE-coated basophils or mast cells
atopic = increased tendency to develop allergies
method?
atopic individuals make IgE to allergens
development of anaphylaxis
- allergen + B cell -> plasma cell producing IgE antibodies
- IgE binds Fc receptors on basophils and mast cells
- Subsequent exposure: antigen crosslinks IgE on baso/mast cell leading to activation and degranulation
anaphylactic death
smooth muscle contraction and edema
Lungs: death bc passages narrow and fill with fluid
Histamine effect
bronchial smooth muscle contraction and increased vascular permeability
Proteases effect
activate matrix metalloproteinases –> cleave tissue matrix proteins and cause damage
TNFalpha
promotes inflammation
Eosinophil chemotactic factor
accumulates at site of ‘injury’ and attempts to counteract the effects of histamine
LTC4 LTD4 and LTE4
leukotrienes
similar effects as histamine, but must be synthesized so it is a sustained, delayed effect
epinephrine because it relaxes smooth muscle is only reversal of anaphylaxis
antihistamines: block binding of histamine
cromolyn sodium and theopylline: block degranulation
type II antibody mediated method
antibody binds directly to tissue and…
1) destroys tissue (cytotoxicity)
2) interupts normal cellular function
examples of type II antibody mediated hypersensitivity
hemolytic disease of the newborn
grave’s disease
myasthenia gravis
Pathogenesis of type III hypersensitivity
- immune complexes lodge in tissues and cause complement activation
- C5a leads to neutrophil accumulation
- lysosomal enzymes in neutrophil damage the tissue
serum sickness
caused by repeat injection of foreign serum (anti-venoms are a good example)
how are immune complexes normally removed?
- RBCs have CR1 protein that binds C3b and C4b on immune complexes
- take the immune complex to liver and spleen where they are removed from blood by macrophages
*in type III this is overwhelmed
delayed-type IV
days after exposure to antigen
requires memory just like all the other ones
may form granuloma or contact dermatitis
Tb skin test