Lecture 4 Flashcards
Define extrinsic asthma
Atopic ‘allergic’, young onset, hyper responsive
Define intrinsic asthma
Non atopic, non allergic, middle aged, hyper responsive, more severe airflow limitation
Define anaphylaxis
Acute severe allergic reaction resulting in respiratory collapse
Define allergy
Changed reactivity
What is an allergy driven by?
T helper lymphocyte subset (Th2 cells) and their products (Th2 cytokines)
Name the cytokines that Th1 produce
Interferon gamma and IL-12
Name the cytokines that Th2 produce
Il-4, Il-3 and il-13, il-5, il-9
In normal airways do th1 or th2 dominate
Th1
What factors favour the th1 phenotype
Present of older siblings
Early exposure to day care
TB, measles, hep A infection
Rural environment
What factors favour the th2 phenotype
Widespread use of antibiotics, western lifestyle, urban environment, diet, sensitisation to house dust mites and cockroaches
What do the T cells do during allergic response
Il-4 and il-13 switch B lymphocytes to make igE antibody. IgE fixes onto the surface if mast cells (sensitisation phase) - process takes a month to occur
What is igE?
Relatively rare immunoglobulin in plasma if you are allergic it will be present in higher numbers
How many asthma cases are not allergic?
30%
What is the sensitisation phase?
Antibodies are present on to the surface of of mast cells this process takes ages to occur
What causes degranulation?
Cross linking igE bound to Fc£R1 on the mast cell
What’s triggers mast deck release and degranulation?
Re-exposure
Name the granule products
Histamine, TNF and other cytokines, proteases and heparins
Does the skin have high or low leeks of histamine
High histamine
Does the lung have high or low histamine levels
Low histamine
Name two membrane derived lipid mediators of inflammation
Leukotrienes and prostaglandins
What is the role of eosinophils in allergy?
Release basic proteins and ROS - responsible for getting rid of the pathogens and microorganisms, they can also damage the airways in the body or the skin in the body
What do eosinophils produce?
Produce cytokines, leukotrienes, and prostaglandins
Name some H1 receptor antagonists
Chlorpheniramine, astemizole, cetrizine
What are H1 receptor antagonists effective in treating?
Allergic rhinitis, urticaria - not effective in asthma as the mast cells in the lungs do not have high levels of histamine
What are chromones?
Mast cell stabilisers - inhibit mediator release from lung mast cells so mast cells are unable to granulate
What are chromones effective for?
Early or late phase asthma
Mode of action of disodium cromoglycate and nedocromil
Inhibit eosinophils chemotaxis
Inhibit sensory nerve fibre excitation and neural reflex - inhibit NKA, BK SO2
- induced bronhcocontriction
