PBL CASE STUDY 2

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  • Created by: Amh
  • Created on: 08-12-15 16:17
What is an allergy
A condition where the immune system becomes hypersenistised to a 'normal particle'
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What class of antibodies are involved in allergies
IgE
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How do IgE antibodies activate mast cells
IgE anibodies bind to FcƐr1 receptors
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What happens when mast cells re activated?
mast cells release the contens of their granule (histamine, PAF, heparin, chymase, tryptase,tumour necrosis factor 2
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What does the histamine do when release from mast cells
makes holes in the mucosal tissue opening pahways from blood vessel to to tissue resulting in swelling. I also acts as a chemoattractan bringing other immune cells over
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What does PAF do
causes vasodilation and clotting
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What does heparin do
removes little bits of the clotting PAF complex so immune cells can get in
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What does tryptase do
causes more mast cell degradation, and therefore amplification
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How does the release of Histamine and other chemical result in anaphylactic shock
histamine causes blood to rush away from your heart to peripheral tissue - lowering bp leading to shock.
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What is urticaria
hives - these are raised red itchy lumps, these cause a burning/stinging sensation, they are a result of a release of inflammatory mediators that resuls in fluid leakage from superficial blood vessels in the upper dermis
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What is angiodema
This is swelling of the deep dermis/subcutaneou/submuosal tissue due to vascular leakag
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What is wheezing dysopea
breathlessness as a result of swelling in the airways
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what is hypotension
low blood pressure
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What are some key methods of allergy testing?
Skin Prick test, skin scratch test, intradermic, skin scrape, blood testing, patch testing, and taking a history.
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what are the 3 types of blood tests for allergies
total IgE count, specific IgE, and component resolved I gE testing
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how does a skin ***** test work
a needle with a small bit of allergens in pressed into skin,, contros are histamine - causes a reaction and glycerin - doesnt cause a reaction
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Why is adrenaline given
Adrenaline can reverse all the symptoms of an anaphylactic shock oit is the first line of response
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What is Adrenalins affect of the alpha adrenoreceptors
It stimulates them causing an increase in peripheral vascular resistance thus improving blood pressure and coronary perfusion, reversing the dilation therefore decreasing angiodema ect
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How does adrenalin affect the Beta-1-adrenoreceptors
It stimulates them having both positive inotropic (increased strength of contraction) and chrnotropic (hear rate) cardiac effects
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How does adrenaline affect the Beta-2-adrenoceptors
Causes bronchodilation as well as increasing intracellular cyclic adenocine monophosphate in mast cells and basophiles, reducing inflammatory mediators
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How do IV steroids work
Steroids reduce swelling and will therefore lessen angiodema and urticaria
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How do antihistamines work
they block H1 and H2 recpeptors - this provides rapid relief of symptoms
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What symptoms are H1 blockers good at relieving
cutaneous symptoms like urticaria
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Give an example of a H1 blocker?
chlorpheniramine
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What is salbutamol
A drug given to reduce wheezing dyspnoea
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How does salbutamol work
It binds to the shor acting beta-2 adrenergic receptors relieving bronchospasm
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What is Ipratropium?
A drug that relieves bronchial spasm (it is an anticholinergic drug)
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How does Ipratropium work?
It blocks M3 type muscinaric acetylcholine receptors in the smooth muscle - opening the bronchi
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What is the structure of antibodies
It is a Y shaped molecule made of 4 polypetide chains. 2 chains are heavy chains, 2 are light. There are variable regions at the end of the heavy and the light chains.
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Are here different types of antibodies
there are 5 classes of antibodies IgM, IgD, IgG, IgE, IgA.
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What determines the class of an antibody?
The constant region
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How do antibodies develop
A T-cell stimulates an immature B cell to mature, and this naive mature B cell produces IgM and IgD antibodies
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What is affinity maturation
It is the effect of repeated exposure to an antigen. It is The mechanism during an immune response that produces antibodies with a strong ability to bind to a foreign antigen over time.
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What are the two processes of affinity maturation
Somatic hypertension, and clonal selection
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What is somatic hyper mutation?
A process whereby heavy and light chain genes of the antibody molecule are mutated at a high rate, leading to diversity in the antibody repertoire. Antibody with greatest affinity for antigen surives
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What is clonal selection?
a specific antigen only activates (i.e. selection) its counter-specific cell so that particular cell is induced to multiply (producing its clones) for antibody production
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What is class switching?
This is where a region in the heavy chain is removed to change the class og n antibody e.g. IgM to IgE
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How does class switching occur?
Via class switching recombination. This is where portions of the heavy chain are removed from chromosome (his occurs in S region) some exons are removed and then the chromosome is reassembled give a dif class
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What initiates class switching?
T cells and cyokins
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What are the key cytokines?
IL4, IL5, IFNy. TGFb
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How many different classes are there of hypersensitivity reactions?
4
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What is a type 1 hype sens reaction?
-depends on an interaction between antigen and IgE antibody attached to mast cells. Eosinophils and a subset of T-cells (Th2 cells) are also involved/ E.g. Hay fever, ashma, peanut hypersens
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What is a type 2 hypersens reaction?
a cytotoxic reaction between tissue- or cell-bound antigen and IgM or IgGantibodies. It occurs in tranfusion reactions
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What is a type 3 hypersens reaction?
an immune-complex reaction between circulating antigen and IgGantibody with subsequent deposition in the walls of blood vessels, joints, kidneys and skin. Resulting in serum sickness
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What is a type 4 hypersens reaction?
a cellular immune response mediated by sensitised lymphocytes
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What class of antibodies are involved in allergies

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IgE

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How do IgE antibodies activate mast cells

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What happens when mast cells re activated?

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What does the histamine do when release from mast cells

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