Lung Immunology Flashcards
What is an allergy?
is an exaggerated immunological response to a foreign substance (allergen) which is either inhaled, swallowed, injected, or comes in contact with the skin or eye
Mechanism not disease
What is an atopy?
hereditary predisposition to produce specific IgE antibodies to common aeroallergens
- Allergic rhinitis, asthma, atopic eczema
What is an intolerance?
presence of symptoms following environmental exposure and/or food ingestion where an immunological mechanism cannot be established.
What is a hypersensitivity?
umbrella term to describe an exaggerated sensitivity to any agent irrespective of the mechanism.
- May be immunological (IgE atopic or non IgE allergic mediated)
- Or non immunological (pharmological, intolerance, enzyme deficiency)
How do atopic allergic conditions arise?
- Individuals produce increased IgE
- Binds to specific FcεR1 and FcεR2 recpetors found on mast cells, blood basophils and dendritic cells
What is the pathophysiology of seasonal allergic rhinitis?
- Sensitization
2. Exposure results in allergic response
What cytokines are released proinflammatory?
Il-4, IL-5
What cells characterize allergic tissue reaction in atopic subjects?
Th2 and eosinophils
What occurs during a Type 1 response?
against viruses, bacteria, fungi and protozoa
recruitment of T helper type 1 (Th1), Th17 cells, cytotoxic T cells, IgM, IgA and IgG subclasses
What occurs during a Type 2 response?
Against Helminth and ectoparasites
Th2 cells, IgE and IgG1 antibodies
Innate immune system: epithelial barriers, innate lymphoid cells, eosinophils, mast cells, basophils and activated macrophages.
What are the 3 types of allergic airway disease?
- Allergic rhinitis (upper airway) - affects 25% of population
- Asthma (lower airway)
- Around alveolar spaces (extrinsic allergic alveolitis)
What are triggers for asthma?
- Allergy e.g house mites, pollen
- Viral infections
- Exercise
- Exposure to fumes or other irritants
- Aspirin
What is the mechanism of asthma?
- Small allergenic particles penetrate to distal airways in alveoli
- Causes release/activation
- Antigen/antibody complexes
- Complement
- Chemotactic factors
- Neutrophils
- Macrophages
- Fibroblasts
What is the principles of treatment of allergic diseases?
- Allergen avoidance
- Anti-allergic medication
- Immunotherapy (desensitization)
○ Subcutaneous
○ Sublingual
How are allergic airway diseases treated depending on severity?
- Avoid allergen
- Antiallergic medication e.g antihistamines for allergic rhinitis and topical corticosteroids for allergic inflammation
- Oral/local non sedative H1 blocker
- Intra nasal steroid
- Specific allergen immunotherapy (hypo/desensitization)
What is the process of specific immunotherapy?
- administering increasing concentrations of allergenic extracts over long periods of time
- Risk for anaphylaxis
What are the pros and cons of allergen injection immunotherapy?
PROS:
Effective
Long lasting immunity
CONS:
Occasional severe allergic reactions
Time consuming
Standardization problems
What is the model of action of specific immunotherapy?
- IgG “blocking antibodies “compete with IgE for allergen
- Prevent aggregation of FcεRI IgE complexes on mast cells through steric hindrance
- Also interfere with antigen trapping by IgE bound to antigen-presenting cells - Inhibit the release of pharmacological mediators from mast cells and basophils
- prevents infiltration of allergic lesions by inflammatory cells and decreases the number of tissue mast cells. - Induce s a shift from a Th2 to a Th1 cytokine profile
- IL-4 and IL5 decreases and the output of IFN-γ and IL-12 increases
- Inhibition of late phase allergic reaction - Induce IL-10 secreting T regulatory cells
- Induction of long-term anergy in allergens specific CD4+ cells
- decreases the number of mast cells + inhibition of eosinophilopoiesis
- May induce non responsiveness
