Immunology - Allergic disease Flashcards
What are the four classifications of hypersensitivity reactions?
Immediate hypersensitivity.
Direct cell killing.
Immune complex mediated.
Delayed type hypersensitivity.
What are the Immune mediated types of adverse food reactions?
IgE mediated - Classical allergy Non-IgE mediated - Coeliac disease - Eosinophilic gastroenteritis - Protein induced enteropathy
Name some generic features of Type 1 allergic disease?
Quickly (1-2 hours)
Stereotyped responses
Presentation influenced by site of contact.
What are some specific features of Type 1 allergic disease?
Asthma Urticaria Angioedema Allergic rhinitis Allergic conjunctivitis Diarrhoea + vomiting Anaphylaxis
What are the cells and molecules involved in allergic disease?
B lymphocytes
- recognise antigen
- produce antigen-specific IgE antibody
T lymphocytes
- Provide help for B lymphocytes to make IgE antibody
Mast cells
- Inflammatory cells that release vasoactive substances
What region of IgE antibodies bind to receptors on Mast Cells?
Fc region links to the Fc receptors.
On first encounter with an allergen what happens?
B cells produce antigen-specific IgE antibodies.
Once the antibodies clear the allergen the remaining IgE antibodies bind to circulating mast cells.
What should happen on a re-encounter with an antigen?
Allergen binds to IgE coating the mast cells.
Mast cell disrupts and releases vasoactive mediators. (Histamine, tryptase, also increased cytokines + leukotrine transcription)
What is classifications Extrinsic asthma?
Response to external allergen.
IgE mediated
Triggers - (e.g. house dust mite, pollen, animal dander)
Associated with other allergic disease
Is intrinsic asthma IgE mediated?
NO.
Intrinsic asthma is non-allergic asthma.
What happens in the lungs when mast cells are degraded and histamine and other inflammatory mediators are released?
Muscle spasms - (Bronchoconstriction (WHEEZE))
Mucosal Inflammation - (Muscle oedema + increased secretions (SPUTUM))
Inflammatory cell infiltrate - (Lymphocytes + eosinophils into bronchioles (SPUTUM YELLOW - CHRONIC))
What is urticaria?
“Hives” “Wheals” “Nettle Rash” “Blisters”
Lesions appear within ~1 hour and lasts 2-6 hours
What is angioedema?
Localised swelling of subcutaneous tissues or mucous membranes.
(Non pitting, no clear demarcation, generally not itchyunless associated with urticaria)
What are some non-allergic causes of mast cell degranulation?
Drugs - Morphine + other opiates. - Aspirin + non-steroidal anti-inflammatories Thyroid disease Idiopathic Physical urticaria - in response to pressure and heat
During acute anaphylactic episode how would you check for evidence of mast cell degranulation?
Serum mast cell tryptase levels
