Hypersensitivity Reactions Flashcards
define hypersensitivity reactions
an antigen specific reaction that is either inappropriate or excessive causing harm to the host
what are the 2 phases in hypersensitivity reactions
- sensitisation phase
2. effector phase
what are type 2 hypersensitivity reactions
where antibodies are produced against cell membrane bound antigens
what are the effects of type 2 reactions
tissue damage and physiological changes
how does tissue damage occur in type 2 reactions
complement cascade - causes neutrophil recruitment, cell lysis and opsonisation
antibody dependant cell cytotoxicity
what is antibody dependant cell cytotoxicity
where natural killer cells binds to the antibodies and release toxic radicals into the cells
what are type 3 hypersensitivity reactions
where the production of immune complexes cause problems due to their deposition in tissues
true or false: membrane bound antigens are targeted in type 3 reactions
false- it is soluble antigens
what antibodies are involved in type 3 reactions
IgG and IgM
what are type 4 reactions
where lymphocytes and macrophages are involved in the reaction
true or false: type 4 reactions are immediate
false - they are delayed
what are the treatments for type 2 reactions
immune suppressants - so that you can’t produce the antibodies
plasmapheresis
splenectomy
receptor stimulators/blockers
what is plasmapheresis
the cleaning of plasma to remove the antigen from blood
what is the treatment for type 3 and 4
non steroidals, corticosteroids and monoclonal antibodies
what type of reaction is involved in Rheumatoid arthritis
type 3
what type of reaction is systemic lupus erthematosus
type 3 - antibody is against Ds-DNA
what type of reaction is glomerulonephritis
type 3 - there is sustained presence of a microbe causing the production of lots of immune complexes
what type of reaction occurs when you transfuse the wrong blood type
type 2
why does a hypersensitivity reaction occur after giving a group blood type
you have naturally occurring antibodies against the other blood types which will destroy foreign RBCs
what type of antibody is involved in blood transfusion reactions
IgM
why can a mother have a child with a different blood type but not have her antibodies attack the Childs RBCs
as the antibodies are IgM,so can’t cross the placenta
what is haemolytic disease of the newborn
when a RH D antigen positive child is being carried in a negative mother. when there blood mixes the mother produces antibodies against the Rh D antigen which attack the Childs RBCs
why can the mothers antibodies against the Rh Antigen reach the child
they are IgG so can cross the placenta
what is myasthenia gravis
where you produce antibodies against the ACh receptors, meaning nervous conductance can’t occur very well
what type of hypersensitivity reaction occurs in myasthenia gravis
type 2
what are the 3 sub types of type 4 reactions
- contact
- tuberculin
- granulomatous
what is contact hypersensitivity
where the antigen binding to the hosts epidermal proteins can cause a reaction
what is tuberculin hypersensitivity
where the TB microbe cannot be removed so granulomas form around it
what is the Mantoux test
injecting a small bit of TB into the skin to see if there is a TH1 response - if there is a small dot it shows the person has already been sensitised
what type of hypersensitivity disease is hashimotos
type 4 and type 2 - as antibodies are produced but there is also a TH1 response
true or false: type 1reactions have a delayed response
false - the response is immediate
what happens during a type 1 reaction
a TH2 response is initiated to produce IgE (instead of the normal TH1 response)
what does the IgE in type 1 reactions do
activates mast cells
where are mast cells usually found
in the skin, GI tract, respiratory tract
name some of the mediators released from the mast cell granules
histamine, leukotriene, platelet activating factor, tryptase
what does histamine do
increases vascular permeability, smooth muscle contraction
what do leukotrienes do
smooth muscle contractions, mucus secretions
describe the sensitisation phase of type 1 reactions
upon exposer IgE is produced which waits on the mast cells
describe the effector phase of type 1 reactions
the antigen causes cross linkage of 2 IgE antibodies, activating the mast cell which they are on
what is urticaria
skin rash
what is angioedema
swelling in the eyes, lips and mouth due to involvement of vasculature
what are the treatment options for type 1 reactions
allergen desensitisation
anti-IgE monoclonal antibody
anti-histamine
leukotriene receptor antagonist
