PT4: Inflammation & Allergy in Asthma Flashcards
what is extrinsic asthma
atopic (allergic), young onset, hyperresponsive
what is intrinsic asthma
non-atopic (non-allergic), middle aged, hyperresponsive, more severe airflow limitation
what is allergy
changed reacticvity
usually used interchangably with immediate hypersensitivity (involves IgE mediated mast cell degeneration, synonymous with ‘atopy’ or ‘atopic diseases’)
what is atopy
allergy
what are allergens
antigens that elicit an allergic response
what is anaphylaxis
acute severe allergic reaction resulting in respiratory collapse
how is an allergy developed
strong genetic influence, allergenic potential, driven by T-helper lymphocyte subset and their products
what Th1 cytokines are involved in allergy
interferon-gamma
IL-12
what Th2 cytokines are involved in allergy
interleukin IL-4 and IL-3 (overlapping receptor usage with very similar actions)
IL-5, IL-9
what factors favour the Th1 phenotype
presence of older siblings, early exposure to day care, TB/measles/hep A infection, rural environment
what type of immunity does a Th1 phenotype give
protective immunity
what factors favour the Th2 phenotype
widespread use of antibiotics, western lifestyle, urban environment, diet, sensitisation to house-dust mites and cockroaches
what is the T-cell direction of allergic response
IL-4 and IL-13 switch B lymphocytes to make IgE antibody
IgE fixes onto FceR on the surface of tissue mast cells
what is IgE
relatively rare immunoglobulin in plasma
E= erythematous antibody
how is the IgE antibody used
Fc region binds with high affinity to FceR1 on mast cells and basophils
cross linking IgE (by antigen) bound to FceR1 on mast cell surface causes degranulation
what is the times course to develop allergy
initial sensitisation may take years; no or very limited symptoms during initial sensitisation and mast cell priming; sensitisation increases over years and re-exposure can trigger mast cell release