Hypersensitivity- type I Flashcards
What is type I hypersensitivity?
Allergy
How quickly does type I hypersensitivity occur?
Immediate
Less than 30 mins
What is an example of a local reaction type I hypersensitivity?
Ingested or inhaled allergens
What is a systemic type I hypersensitivity reaction?
Insect sting or IV administration
What are the antigens in type I hypersensitivity?
Environmental
Non- infectious antigens
What are domes examples of allergens in type I hypersensitivity?
Tree and grass pollen House Dust mite Animal dander Fungal spores Insect venom Medicines Chemicals like latex Foods
What are the mechanisms that type I hypersensitivity uses?
Abnormal adaptive Immune response against the allergens e.g. T helper 2 response, IGE production
Mast cell activation- sensitised Individuals
Who is more at risk to allergies, developing countries or westernised countries?
Westernised as:
Smaller family, urban homes, intestinal microflora stable, high antibiotic use, low or absent helminth burger, good sanitation low orofaecal burden
TH2 response
Should children be exposed to microbes?
Yes as protected against allergic disease
What is the most serious type of allergy?
Anaphylaxis
Why wouldn’t a man stung by a bee have died the first time but did die the second?
Sensitised
What is dysbiosis?
Compositional and functional alterations of microbiome
What is microbiome?
The complete genetic content of all the microorganisms that typically inhabit in the body such as skin or gastrointestinal tract
What is the therapy for type I hypersensitivity?
TH2 response- allergen desensitisation
IGE- anti IGE monoclonal antibody
Anti histamine, leukotriene receptor antagonists, corticosteroids
What is immunotherapy?
Administaryionof increasing doses of allergen extracts over a period of years by injection or drops or tablets under the tongue
What are the potential mechanisms of immunotherapy?
CD4+CD25 Regulatory T cells
Shift from TH2 to TH1
Inhibitory anti-inflammatory cytokines Allergen specific blocking IgG
Is there a genetic part to allergy?
Yes
What do children in large families have lower risk of?
Hay fever and eczema
What does upper respiratory tract infection protect against?
Allergic sensitisation and asthma in later life
Shou,d you get your child a pet?
Yes as less likely to develop asthma
What does western life cause to mucosal surfaces?
Alteration of the symbiotic relationship with parasites and bacteria leading to dysbiosis of the microbiome at mucosal surfaces
What will alteration of your normal flora?
More likely to get allergies
What can cause loss of microbiota diversity?
C section by x8
City
Antibiotics
Food
What do mast cells release?
Histamine
Trytase
Leukotrienes
Platelet activating factor
What kind of mechanism does a mast cells have?
IGE dependant
What is important in division of mast cells?
Stem cell factor
Where are mast cells?
Mucosal and epithelial tissues e.g. GI tract, skin, respiratory epithelium
Connective tissue surrounding blood cells
What is a trigger to activate mast cells?
Cross linking IGE
What can mast cell degranulation cause?
Increased vascular permeability
Vasodilation
Bronchial constriction
What is the skin manifestation of allergic reactions?
Within epidermis is urticaria
What is deep dermis manifestation in allergy look like?
Angiodema
What happens in anaphylaxis?
Hypotension Cardiovascular collapse Generalised urticaria Angioedema Breathing problems Many more
