L62. Hypersensitivity Flashcards
What is hypersensitivity?
A state of altered reactivity when the body reacts which an exaggerated response to a foreign agent.
What type of reaction is an allergy?
Hypersensitivity type 1
What is an allergen?
An antigen which causes an allergic reaction.
Are allergies and intolerances the same thing?
No
Briefly describe type 1 hypersensitivity.
Rapid response to allergen called “immediate hypersensitivity”. It is mediated by IgE.
What is Aptoy?
A genetic predisposition to allergy which can lead to anaphylaxis.
What are haptens?
small molecules recognised by antibodies but cannot initiate an immune response eg. skin rash in a contact allergy. Haptens must be chemically attached to a carrier molecule.
Describe the role of IgE in allergen recognition.
IgE producing B cells are activated on first exposure. B cell class switching occurs. IgE binds to the mast cell receptor. It recognises the allergen. On next contact, it binds and causes degranulation.
Name 2 forms of type 1 hypersensitivity.
Cutaneous atopy (localised) eg. hayfever, asthma Systematic anaphylaxis (systematic) eg anaphylactic shock (from mast cell degranulation)
Name 2 types of allergy testing.
Skin prick/patch test for skin reaction only Blood test (measures IgE)
Name 2 anti-allergy drugs and how they work.
Antihistamines (compete with histamine for receptors)
Epinephrine (immediate anaphylaxis treatment as a vasoconstrictor and muscle relaxer)
Give an example of an immunological treatment
Hypo-/de-sensitisation by repeat allergen injections
Which classification is used for hypersensitivity?
“Gell and Coombs classification”
Briefly describe type 2 hypersensitivity.
Activation of complement by IgM or IgG.
Cell is lysed by natural killer cells or CD8+ T cells eg transfusion reactions (from mis-matched blood types)
Briefly describe type 3 hypersensitivity.
They are reactions against soluble antigens circulation in serum.
Antibody-antigen immune complexes lead to complement and neutrophil recruitment.
