Allergic Diseases Flashcards
What type of Hypersensitivity causes anaphylaxis?
Type 1
What type of hypersensitivity is caused by IgG antibodies?
Type 2 and Type 3
How does IgE antibody cause allergic reaction?
Mast cell activation
What is the atopic triad?
eczema, hayfever, and asthma – the atopic triad because they so often occur together.
Pathophysiology of asthma and rhinitis?
- Exposed to allergen
- Inflammation of upper and lower airways
- Nasal congestion
- Tonsillar and adenoidal enlargement
- Narrowing of nasopharyngeal area
- Oedema and mucus in lungs
- Airway constriction and hyperreactive airways
Rhinitis; what are initial symptoms?
- Blocked/runny / itchy nose
- Sneezing
- Often with eye symptoms (itching, burning, watery eyes, redness)
What are the 2 types of rhinitis?
Allergic and non-allergic
What type of hypersensitivity is allergic rhinitis?
Type 1
What is allergic rhinitis mediated by?
exaggerated IgE mediated immune responses
What do type 1 hypersensitivities include?
- Atopic diseases, which are an exaggerated IgE mediated immune responses (i.e., allergic: asthma, rhinitis, conjunctivitis, and dermatitis)
- Allergic diseases, which are immune responses to foreign allergens (i.e., anaphylaxis, urticaria, angioedema, food, and drug allergies).
Describe type 1 hypersensitivity. What is it mediated by?
Is also known as an immediate reaction and involves immunoglobulin E (IgE) mediated release of antibodies against the soluble antigen. This results in mast cell degranulation and release of histamine and other inflammatory mediators.
What can allergic rhinitis then be classified into?
Seasonal or perennial rhinitis
Treatment for allergic rhinitis?
Antihistamines and intranasal steroids
What is asthma?
•isease of inflammation & hyper-reactivity of small airways
What is an aeroallergen?
any airborne substance, such as pollen or spores, which triggers an allergic reaction
In childhood, which aero-allergic stimuli are of key pathogenic importance in asthma?
house dust mite
What are the immediate symptoms of asthma mediated by?
IgE-mediated
Damage to airways can be caused by the late phase response of asthma. What are damaged airways then hyperreactive to?
Non-allergic stimuli e.g. fumes
Pathogenesis of asthma?
- Allergen presented to APC
- APC induces T cell proliferation and differentiation into Th2 cells
- Th2 cells secrete cytokines (IL4, IL-5, IL-13)
- IL-5 induces eosinophils, causing proliferation
- IL-4 and IL-13 stimulate B cells maturation to plasma cells which secrete IgE antibodies
- IgE antibodies activate mast cells and basophils
- Allergic reaction
What do mast cells release?
- Histamine
- proteases
- prostaglandin D2
- leukotrienes
- a variety of cytokines
Which cytokines do Th2 cells release during asthma?
IL4, IL-5, IL-13
What is effect of IL-4?
- Stimulation of activated B-cell and T-cell proliferation
- Differentiation of B cells into plasma cells
- IL-4 drives the immunoglobulin (Ig) class switch to IgG1 and IgE and up-regulates MHC class II production.
What is effect of IL-5?
- Stimulates B cell growth and increases immunoglobulin secretion - primarily IgA
- It is also a key mediator in eosinophil activation.
What is effect of IL-13?
The overexpression of IL-13 induces many features of allergic lung disease, including airway hyperresponsiveness, goblet cell metaplasia, mucus hypersecretion and airway remodelling which all contribute to airway obstruction.