lung infection and immunity Flashcards
allergic airway diseases: define the terms allergy, intolerance, atopy and hypersensitivity; explain immunological mechanisms operative in allergic airway diseases (including allergic rhinitis, asthma, extrinsic allergic alveolitis); recall the epidemiology, explain the aetiology and explain principles of treatment of allergic airway diseases
locations of allergic airway diseases (allergic rhinitis, asthma, allergic alveolitis)
upper airways (allergic rhinitis), bronchi (asthma), aveoli (allergic alveolitis)
define hypersensitivity
exaggerated response to foreign substance (immunological or not)
immunological exaggerated response
allergy - IgE-mediated (atopic diseases such as hayfever), non-IgE-mediated allergic diseases
non-immunological exaggerated response
intolerance, enzyme deficiency, pharmacological
define allergy
exaggerated immunological response to allergen (inhaled, swallowed, injected, comes in contact with skin/eye); mechanism, not disease; important role in some diseases all or some of the time
allergy: early and late response (cells and signs)
early: mast cells, basophils causing watery eyes, itchy nose etc.; late: eosinophils, T cells causing nasal congestion
aetiology of seasonal allergic rhinitis
sensitisation → 2nd (chronic) exposure after several seasons → allergic response; if allergic nasal epithelium disrupted, innate then adaptive response
allergy: 3 cytokines and major cell
IL-4, -5, -13; eosinophils
define atopy
hereditary predisposition to produce IgE antibodies vs common environmental allergens
what are the 3 atopic diseases
allergic rhinitis, asthma, atopic eczema
what are allergic tissue reactions in atopic subjects characterised by
infiltration of Th2 cells (IL-9) and eosinophils
what causes allergic rhinitis
can be seasonsal; commonly caused by many animals (pets, cockroaches) and pollen
features of asthma
very heterogeneous; based on control, severity or endotype/endo-phenotype
asthma severity scale
intermittent, persistant, chronic
endotypes of asthma
allergic, atopic or eosinophilic; neutrophilic; exercise-induced
extrinsic allergic alveolitis mechanisms
small allergens penetrate to distal airways and enter alveoli → formation of antigen/antibody complexes → complement, neutrophils, macrophages, fibroblasts triggered and lymphocytes recruited
3 principles of treatment of allergic disease
allergen avoidance, anti-allergic medication (e.g. anti-histamines, corticosteroids), immunotherapy (allergen-specific immunotherapy)
advantages of allergen-injection immunotherapy
effective, long-lasting immunity
disadvantages of allergen-injection immunotherapy
occasional severe allergic reaction, time consuming, standardisation problems
features of allergen immunotherapy
modulate dendritic cells, deviation (Th2 to Th1 cells, Th cells to Treg that inhibit TfE cells), induction of regulatory responses and IgG to prevent IgE from cross-linking basophils and mast cells to produce an allergic reaction, desentising to allergens
allergic rhinitis mechanism
allergens pass over epithelium and captured by dendritic cells → migrate to lymph nodes → stimular Th cells to differetiate to Tfh (IL-4) and Th2 (IL-9) → activate B cell and mast cell respectively → allergen specific IgE antibodies released → bind to mast cell FcE receptors → allergen cross links IgE antibodies, degranulation occurs → histamine release
epidemiology of allergic rhinitis
affects up to 25% of the population
epidemiology of asthma
affects up to 10% of the population
