Hypersensitivity 1 Flashcards
(29 cards)
How many types of hypersensitivity are there?
4
Type I hypersensitivity?
Allergy
Type II-IV hypersensitivity?
Autoimmunity
Type II hypersensitivity?
Autoantibodies
Type III hypersensitivity?
Deposition of immune complexes
Type IV hypersensitivity?
T cell mediated tissue injury
What do allergens do to the innate immune response?
“skip it”
How does an allergen cause a reaction?
It crosslinks IgE antibodies, degranulating the MAST cell
How do mast cells exist normally?
“pre-primed” with IgE bound to the surface via FC receptors
What happens when a MAST cell is degranulated?
Histamine release, cytokine release
What can MAST cell mediators cause?
Increased vascular permeability
Vasodilation
Bronchial and smooth Muscle con
Local inflammation
Why do allergic reactions increase over time?
formation of memory b cells forming after the first time
What are allergies treated with?
Anti-histamines e.g. cetirizine
What do allergens require before the substance triggers an immune response?
Repeated exposure
Characteristics of many allergens?
small, glycosylated molecules w/ high solubility in body fluids
Why is there no TH1 or macrophage activation in allergies?
They don’t trigger the innate response
Why do allergens need repeating units?
They need to cross link IgE antibodies on MAST cell surface–> bind to more than one antibody at once
Why do allergens not trigger the innate response?
Dont have anything that would trigger pattern recognition receptors–> LPS, etc
How many mechanisms can autoantibodies act by?
3
First way of autoantibodies acting (complement)?
Autoantibody activating complement and stimulating phagocytosis
Second way of autoantibodies acting (neutrophils)?
Autoantibodies recruiting neutrophils which cause tissue damage
What is graves disease?
Producing antibodies against thyroid stimulating hormone receptor
Mechanism of myasthenia gravis?
Antibodies block the nicotinic ACh receptors on muscle
Outcome of myasthenia gravis?
muscle weakness especially in eyelids
