L27-Allergic disease and parasite immunity Flashcards
What is a hypersensitivity response?
A reaction of the immune system that is detrimental to the host.
What are hypersensitivity reactions usually in response to?
Usually against antigens derived from relatively innocuous substances such as pollen. These are known as allergens.
What are the 4 different types of hypersensitivity reaction?
Type I- IgE mediated mast cell degranulation
Type II - IgG autoantibody causing direct damage
Type III - IgG/antigen immune complex damage
Type IV - T cell mediated
What type of reaction is hay fever an example of?
Type I
What type of reaction is Lupus an example of?
Type III
What type of reaction is contact dermatitis an example of?
Type IV
What type of reaction is myasthenia gravis an example of?
Type II
What are types II and III usually grouped as?
Autoimmune disease
What does the term allergy refer to?
Type I, IgE mediated reactions
How quickly do type I and type IV reactions occur after exposure?
Type I is immediate
Type IV is greater than 4 hours and often after a day or two
What has to happen on first exposure to the allergen for the body to become allergic to it?
IgE class switching must occur due to the presence of certain cytokines. This means when the antigen is re encountered then the patient can have an IgE mediated reaction.
What is the definition for anaphylaxis?
A severe, life-threatening, generalised or systemic hypersensitivity reaction.
What skin changes sometimes occur with anaphylaxis?
Urticaria or angioedema but are not present in 20%
How do you treat anaphylaxis?
By giving adrenaline.
Antihistamines and steroids are given to try and prevent a biphasic reaction
How often is adrenaline readministered?
It can be repeated every 5 mins as it has a short half-life
