Immediate hypersensitivity Flashcards
What is immediate hypersensitivity?
A type I hypersensitivity reaction caused by IgE production and mast cell activation
What is atopy?
A genetic predisposition to produce IgE antibodies in response to environmental allergens and develop strong hypersensitivity reactions
What are common IgE-mediated allergic diseases?
Hay fever asthma eczema urticaria and allergic conjunctivitis
What is asthma in the context of hypersensitivity?
An immediate hypersensitivity reaction in the lungs causing reversible airway obstruction and bronchial inflammation
What are the symptoms of immediate hypersensitivity reactions?
Itchy skin rashes sneezing runny nose coughing wheezing red eyes swelling vomiting and diarrhea
What is anaphylaxis?
A systemic immediate hypersensitivity reaction characterized by edema bronchoconstriction and hypotension
What are common allergens in immediate hypersensitivity?
Dust mites tree and grass pollen food proteins such as peanuts animal dander and drugs
What is the mechanism of immediate hypersensitivity?
Allergen exposure activates Th2 cells leading to B cell class switching to IgE IgE binds to mast cells and re-exposure triggers mast cell degranulation
What cytokines are involved in IgE class switching?
IL4 and IL13 secreted by Th2 cells promote IgE production by B cells
What mediators are released by mast cells in hypersensitivity?
Histamine platelet-activating factor leukotrienes prostaglandins and cytokines
What are the early and late-phase responses in immediate hypersensitivity?
The early phase includes vasodilation edema and bronchospasm while the late phase involves cellular recruitment and inflammation
What is the role of eosinophils in immediate hypersensitivity?
Eosinophils are recruited by IL5 and release toxic proteins such as major basic protein causing tissue damage
What are the effects of histamine in hypersensitivity?
Bronchoconstriction vasodilation increased vascular permeability and stimulation of nerve endings causing itching
What is the hygiene hypothesis in allergy development?
A lack of early exposure to infectious agents and parasites increases susceptibility to allergies by suppressing immune development
How is anaphylaxis treated?
With adrenaline to reverse bronchoconstriction and vasodilation and antihistamines to block histamine receptors
What are common treatments for asthma in hypersensitivity?
Corticosteroids to block inflammatory cytokines and sodium cromolyn to inhibit mast cell mediator release
What is the role of Th2 cells in immediate hypersensitivity?
Th2 cells secrete IL4 IL13 IL5 and eotaxin promoting IgE production and eosinophil recruitment
What is the genetic basis of atopy and IgE production?
Atopy is influenced by multiple genes including those encoding IL4 IL5 IL13 and Fc receptors
What is the role of eotaxin in hypersensitivity?
Eotaxin attracts eosinophils to sites of inflammation
How does dust mite allergen trigger hypersensitivity?
Dust mites produce proteins that can penetrate mucosal barriers and trigger IgE production
What cytokines are involved in the late-phase response of hypersensitivity?
IL3 promotes mast cell proliferation TNF-alpha promotes inflammation and IL5 recruits eosinophils
How do mast cells contribute to hypersensitivity reactions?
Mast cells release pre-formed mediators synthesize new mediators and produce cytokines during allergic responses
What is the clinical course of immediate hypersensitivity reactions?
The immediate phase occurs within minutes while the late-phase reaction peaks hours after allergen exposure
What is the focus of drug therapy for immediate hypersensitivity?
Blocking mast cell degranulation and the effects of mediators and cytokines
