Hypersensitivity Flashcards
(21 cards)
What is meant by hypersensitivity?
Exaggerated/ inappropriate immune responses
What does type 1 hypersensitivity involve?
IgE mediated reactions
IgE secreted usually
3 phases of type 1 hypersensitivity
Sensitisation phase
Activation phase
Effector phase
What is meant by sensitisation phase?
Exposure to allergens - activate the Th2 cells-stimultae B cells to form IgE plasma cells
IgE produced in response to antigenic stimulus and binds to Fc receptors on most cells and basophils
What is meant by activation phase?
R-exposure to antigen triggers mast cell and basophils to respond by release of granules
What is meant by the effector phase?
Complex response occurs as a result of histamine and other pharamcologicallt acitve agents releasednby mast cells and basophils
Test for type 1 hypersenstivity reaction
Wheat and flare response
RAST-serum sample
GI physiological effects of mast cell degranulation
Increase in fluid secretion
increase in peristalsis
can lead to expulsion of GI tract contents
ENT physiological effects of mast cell degranulation
Decreased diameter of airways leading to and increase in the amount of mucus
swelling can lead to congestion of the airways
Blood vessels physiological effects of mast cell degranulation
Increase in blood flow increase in permeability increase in lymoh increase in fluid hypotension than can lead to an anahylatic shock
what is meant by atopy?
Localised - reaction targets specific tissues/organs
What is the immediate phase in type1 hypersentiivity
IgE mediated mast cell activation
What is meant by the late phase in type1 hypersensiitivity
Depending on allergen dose - sustained activation of mast cells
What is type 2 hypersensitivity?
antibody mediated destruction of cells
What are causes of haemolysis?
Blood transfusions
Haemolytic disease of the newborn
Drug induced haemolytic anaemia
How does TII hypersensitvity reactions occur?
Antibody binds to antigen on surface of target cell
Fc receptot on NK cells recognise AB
corss linkage cells target cell leading apoptosis
How does TIII hypersensitivity occur?
WHenever immune complexes are deposited
What happens during TIII hypersensitivity?
Recruitment of neutrophils to the site and lytic enzymes cause tissue damage
examples of TIII hypersensitivity
Farmers lung
Pigeons fancier disease
Serum sickness
What is Type IV hypersensitivity?
Localised inflammation produced by Th cells
large influx of inflammatory cells and macrophages
if antigen is not easily phased
What are the stages of prolonged Delayed - type hypersensitivity?
Macrophages adhere to each other Fuse to form multinucleated giant cells Form palpable nodules release lytic enzymes tissue damage
