1.2 type I hypersensitivity Flashcards
what are the features of a type I hypersensitivity reaction?
ALLERGY
- immunological basis for different diseases
- immediate reaction (<30mins)
- antigens/allergens
name some examples of allergens in type I hypersensitivity reactions
- trees and grass pollen
- house dust mite
- cats and dogs
- fungal spores
- insect venom
- medicines
- chemicals e.g latex
- food e.g nuts
what are the mechanisms of type I hypersensitivity reactions?
abnormal adaptive immune response against allergens
- IgE production
- TH2 response and interlukins
mast cell activation
- binds against harmless antigen
- in sensitised individuals
- different clinical allergic disorders dependant of mast cell location
where are most mast cells strategically located?
most mucosal and epithelial tissue = GI tract, skin, respiratory epithelium
in CT surrounding blood cells
what is the immune mechanism for an allergic reaction?
allergen 1st exposure
- TH2 response, make IgE
allergen 2nd exposure
- IgE cross lining
- mast cell degranulation = histamines and chemokine released
- result = increased vascular permeability, vasodilation and bronchial constriction
what is urticaria?
a skin manifestation of allergic reactions
skin looks patchy
caused by mast cell activation within the epidermis
mediators = histamines and cytokines/leukotrienes
if prolonged and chronic exposure = atopic dermatitis and eczema
what is a facial manifestation of allergic reactions?
angioedema
non itchy swelling
caused by mast cell activation in deep dermis
mediatiors = histamine and bradykinin
what are the systemic manifestations of allergic reactions (anaphylaxis)
increased vascular permeability =
hypotension
cardiovascular collapse
generalised urticaria
Vasodilation =
angioedema
bronchial constriction =
breathing problems
others include
- headache
- anxiety
- cramps
- hives/itchy
- loss of bladder control
how do you treat anaphylactic shock and what does it do?
treat with epinephrine (adrenaline)
- reveses peripheral vasodialtioon, oedema, and alleviates hypotension
- reverses bronchospasm
- increases force of myocardial contraction
- inhibits mast cell activation
it is a timesaver. get the person to the hospital ASAP
what therapies can be used against type I hypersensitivity reactions?
against mast cell activation
- corticosteriods
- antihistamines
- leukotriene receptor antagonists
as well as
- anti- IgE monoclonal antibody
what are important factors for the development of allergic diseases?
- reduced infectious burden
- changes in micro biome
