Lecture 4 - immunopathology + hypersensitivity Flashcards
(31 cards)
what is allergy?
a reaction produced by the normal immune system (directed against innocuous antigens) in a pre-sensitised (immune) host
innocuous antigen
self tissue which the immune system recognises as foreign because it is overreacting
dendritic cell
cell that engulfs and presents material in its environment
T lymphocyte
engage and secrete chemicals
B lymphocytes
make antibodies
what type of antibody is involved in type 1 hypersensitivity?
IgE
what is the immunopathogenesis of type 1 hypersensitivity?
- IgE medicated mast cell and basophil degranulation
- release of preformed and de novo inflammatory mediators
what are the clinical features of type 1 hypersensitivity?
- fast onset
- weal and flare
which cells are involved in the late phase response of type 1 hypersensitivity?
- Eosinophils
- Th2 T cell –> a coordinator in this reaction
what is the primary response of type 1 hypersensitivity?
degranulation and releases:
- histamine
- proteases
- chemotactic factors
what is the secondary/ late (lipid mediators) response of type 1 hypersensitivity?
release:
- prostaglandin
- leukotrienes
what is released when IgE and receptor on mast cell cross link?
histamine, proteases, chemotactic factors by degranulation
cause symptoms of allergic reaction
what are the effects of histamine?
- bronchoconstriction
- increasing permeability of capillaries = swelling + lower BP
- swelling and inflammation, throat esp.
- increase HR
- may have blood clots, -gastric acid secretion
- diarrhoea
what are the 3 types of type 1 hypersensitivity?
- mild–> runny nose, itch, skin symptoms
- moderate
- severe –> anaphylaxis
anaphylaxis
an acute, potentially life-threatening, IgE medicated systemic hypersensitivity reaction
a medical emergency
urticaria
hive like over the skin
what are the symptoms of mild type 1 hypersensitivity?
- ichy eyes or nose
- cutaneous pruritus
- flushing
- urticaria
- oral tingling/pruritus
- abdo pain/naudea/vomiting
- runny nose, sneezing
what are the symptoms of moderate-severe type 1 hypersensitivity?
Anaphylaxis symptoms: prfound systemic reactions
- diffuse uriticaria and angioedema
- severe abdominal pain
- vomiting diarrhoea
- hoarseness cough
- SOB
- wheezing and cyanosis - respiratory arrest
- hypotension
- dizziness , loss of consciousness
- low BP
what is the first step in sensitisation reaction?
allergen presented to dendritic cells and presented to naive T cells
what do T cells differentiate into in sensitisation reaction?
Th2 cells
what do Th2 cells secrete in sensitisation reaction?
cytokines IL-4 and IL-13
what is the function of IL-4 and IL-13?
act as signal to naive B cells
what do naive B cells differentiate into in sensitisation reaction?
memory B cells with specific IgE that will recognise the allergen on further exposure
what is the change from B cell to memory cells called?
class switching because it moves from making IgM to IgE
