Hypersensitivity Flashcards
How many mechanisms of hypersensitivity are there
4
what are the 2 phases of hypersensitivity
sensation stage
pathological stage
What happens during the sensation stage
Immune response occurs as result of binding to an antigen
what happens during the pathological stage
immune system drives tissue damage in response to immunological mechanisms
What immune cells are involved in the allergic response
IgE
mast cells
eusinophils
what effector cells are involved in the allergic immune response
TH2
How are allergic responses regulated?
regulatory T cells
parasites secrete factors which can dampen the immune system
What can cytokines secreted by TH2 cause other cells to do
cause plasma cells to class switch produced IgE antibodies
cause recruitment of eusoniphils
How is the half life of IgE antibodies prolonged
by binding to receptors on basophils and mast cells
What happens when a basophil bound to IgE re-encounters an allergen
fast response
degranulation
release histamine
What is the allergic phase
release of histmaine
increased expression of pro-inflammatory cytokines
What is the hygiene hypothesis
cleaner environment - less exposure to microbes
immune system is not “trained” well
What parts of the body are commonly effected by allergens
lungs (bronchioles)
skin
gut
What skin condition is called by allergens
urticaria
what respiratory condition is caused by allergens
asthma - restriction of the bronchioles
How can the type 1 hypersensitivity response be managed
prevention of degranulation
anti-inflammatory agents
steroids - dampen immune system
Which hypersensitivity mechanism uses surface/membrane bound antigens
Type 2
How is type 2 hypersensitivity activated
IgM
IgG
antibodies directed towards antigens on cell surface
What are the possible results of type 2 reactions
destruction of cells with ‘positive’ self antigens
How are self-cells killed in type 2 sensitivity
antigen-antibody complex acts as an opsonin
phagocyte engulfs cell
What complement system can be activated as result of type 2
classical
What happens if an antibody binds to a thyroid cell during type 2 mechanism
can cause an overactive thyroid
What type of antigens are involved in the type 2 mechanism
membrane/self-cell surface
How does a type 3 mechanism occur
soluble antigen-antibody complexs
get lodged in capillaries between endothelial cell and basement membrane
What can the type 3 mechanism activate
classical complement pathway
vasodilation
neutrophils attracted to area
How does the type 3 mechanism cause massive inflammation
neutrophils gather at site
discharge killing methods
promotes inflammation/tissue death
What is the type 4 mechanism also known as
delayed type hypersensitivity
Which immune cell drives type 4
CD4+T
What effector cells in involved in type 4
TH1
What does the activation of CD4+ cause
proliferation and differentiation into TH1
macrophage recruitment/activation
What are the classical signs of delayed type hypersensitivity
large number of macrophages at site
granulomas
How do granulomas form
pathogens/foreign bodies that can’t be cleared
How are TH1 cells activated
antigen presenting macrophages
which hypersensitivity mechanism is not directly driven by antibodies
type 4
