Allergy Flashcards
What happens in allergy?
Binding of allergens to preformed igE antibodies on the surface of mast cells and basophils
IgE binds to
FcepsilonR1
If you have more than one IgE bounds to allergen then?
Clustering of receptors , intracellular portion of receptor is phosphorylated, which leads to intracellular cascade and cellular activation.
This in turn causes mast cell to degranulation releasing histamine, tryptase
Leukotrienes are produced from/
Arachidonic acid being converted by lipoxygenase
Membrane phospholipids are converted to arachidonic acid by?
Phospholipase a2, which is created through inflammation, mast cell activation
What are effects of mast cell activation?
Gastro- increased fluid secretion/ peristalsis
Airway- decreased diameter and. Increased mucus secretion
Blood v- increase blood flow, permeability
Anaphylaxis causes?
Generalised vasodilatation, and fluid loss from circulation to tissue as a result of histamine release
Signs of anaphylaxis?
Hives, angiodema, vomiting diarrhoea, hypotension, vasodilatation, laryngeal oedema bronchocondtriction
Most common type of food allergy?
Oral allergy syndrome
Oral itching- mainly rosacea fruits
Changes in asthmatic airway?
Thickened basement membrane and smooth muscle hyperplasia
Late phase shows?
Infiltration with inflammatory cells, CD4 T cells, eosinophils, and mast cells
Starts 4 hours after early phase and finishes within 4 hours
Th1 secrete
IFN g
TH2 secrete?
Il 4, 5 9 and 13
Th17 secrete?
Il 17, for defence against bacteria and fungi
TH2 responses are needed in allergy?
Il4- b class switching to igE
IL4 and 13 promote mucus hypersecretion
Il5 for eosinophils survival
Il9 recruits mast cells
Hygiene hypothesis?
Small family size, low infection burden, good sanitation,
So more likely to develop allergic disease
In low hygiene levels immunity is skewed to?
TH2 to th1
Induce production of regulatory T cells
Leap study?
High risk infants to peanuts
At 6 months randomised to regular consumption or avoidance
Children have greater allergy in avoidance
Theory is they meet it through the skin, increase in TH2
But in gut, t regs
Skin testing?
Drops of allergen, top layers of epidermis punctured with lancet
Wheal with flare in 15 mins
Radioallergosorbant assay, now by Elisa?
Allergen on the plastic add in the serum. Antibodies igE sensitised bind to allergens.
Secondary antibody anti iGE to detect with a marker
Symptoms relievers?
Act on pathways
B2 agonist salbutamol- b2 adrenoreceptors cause smooth muscle relaxation
Epinephrine- oppose vasodilatation and bronchoconstiction
Nasal decongestant- oxymetazoline
Act on alpha 1 adrenoreceptors, cause vasoconstriction
Direct affecting pathway
Leukotriene receptor antagonist (only used for asthma)
H1 antihistamine
Mast cell stabilisers (for eye drops rhinitis)
Example of mast cell stabiliser
Sodium cromoglycate
Topical use only
Short half life
Leukotriene receptor antagonist example
Montekulast, beneficial in chronic asthma
Monoclonal antibody against igE?
Omalizumab atopic asthma
Allergen specific immunotherapy works how?
Reduce TH2 responses
Induced allergen specific igG antibodies
Reduction i mast cell responsiveness
Reduced allergen specific igE levels
