Immunopathology 1 Flashcards
what is hypersensitivity?
host tissue injured during immune response to a foreign antigen
how many types of hypersensitivity are there and how are they classified?
4 types
coombs and gell classification
what is the immune reactant of type 1 hypersensitivity?
IgE
what is the immune reactant of type 2 hypersensitivity?
IgG
what is the immune reactant of type 3 hypersensitivity?
IgG
what is the immune reactant of type 4 hypersensitivity?
TH1 cells/TH2 cells/CTL
what is the antigen of type 1 hypersensitivity?
soluble antigen
what is the antigen of type 2 hypersensitivity?
cell/matrix-associated antigen
or
cell-surface receptor
what is the antigen of type 3 hypersensitivity?
soluble antigen
what is the antigen of type 4 hypersensitivity?
soluble / cell-associated antigen
what is the effector mechanism of type 1 hypersensitivity?
mast cell activation
what is the effector mechanism of type 2 hypersensitivity?
Complement FcR+ cells (phagocytes/ NK cells)
(cell/matrix-associated antigen)
antibody alters signalling (cell-surface receptor)
what is the effector mechanism of type 3 hypersensitivity?
complement, phagocytes
what is the effector mechanism of type 4 hypersensitivity?
macrophage activation (TH1 cells)
IgE production, eosinophil activation (TH2 cells)
cytotoxicity (CTL)
what is an example of a hypersensitivity reaction of type 1 hypersensitivity?
allergic rhinitis, asthma, systemic anaphylaxis
what is an example of a hypersensitivity reaction of type 2 hypersensitivity?
drug allergies e.g. penicillin (cell/matrix-associated antigen)
or
chronic urticaria (cell-surface receptor)
what is an example of a hypersensitivity reaction of type 3 hypersensitivity?
serum sickness/arthus reaction
what is an example of a hypersensitivity reaction of type 4 hypersensitivity?
contact dermatitis (TH1 cells)
chronic asthma (TH2 cells)
graft rejection (CTL)
what is localised type 1 hypersensitivity?
hay fever, asthma
what is generalised type 1 hypersensitivity?
anaphylaxis
what is the mechanism of type 1 hypersensitivity?
allergen binds to IgE on mast cell (containing heparin and histamine) -> crosslinks 2 receptors -> activates cell -> degranulation
when mast cells are activated and degranulate, what is the effect on the gastrointestinal tract?
increased fluid secretion
increased peristalsis
diarrhoea/vomitting
when mast cells are activated and degranulate, what is the effect on the airways?
increased diameter increased mucus secretion congestion of airways coughing/phlegm swelling and mucus in nasal passages
when mast cells are activated and degranulate, what is the effect on the blood vessels?
increased blood flow
increased permeability
increased fluid in tissues -> increased lymph to lymph nodes -> increased cells and protein in tissues, increased effector response in tissues
what are the risk factors for the development of a food allergy?
immature mucosal immune system
early introduction of solid food
hereditary increase in mucosal permeability
IgA deficiency or delayed IgA production
what do antibodies bind to in type 2 hypersensitivity?
bind to normal or altered cell surface markers recognised as non-self
in what situations does type 2 hypersensitivity occur?
blood transfusion reaction
haemolytic disease of the newborn
what is the mechanism of type 2 hypersensitivity?
binding to a target -> activates killing mechanisms ->
complement -> lysis
or
phagocytes -> phagocytosis
what is haemolytic disease of the newborn?
RhD- mother
RhD+ baby
baby makes RhD+ cells
mother makes anti-RhD- by B cells
next pregnancy these antibodies attack the foetus and lyse foetus red blood cells
how does a direct antiglobin test work?
no agglutination - anti-human Ig doesn’t bind to RBC
agglutination - anti-human Ig binds to RBC and breaks it down