Hypersensitivity Flashcards
Types of hypersensitivity reaction
Type I-III = antibody mediated
Type IV = cell mediated
Type I hypersensitivity
The cause of anaphylactic shock
Mediated by IgE antibodies which cause mast cell activation
Stimulated by soluble antigen
Following initial exposure to antigen, IgE antibodies remain bound to mast cells, so subsequent exposure to the antigen causes rapid degranulation
Allergic rhinitis
A type I hypersensitivity reaction
Allergen is collected and presented to Th2 cells
This causes release of IL-3, IL-4 and IL-5 which cause class-switching, resulting in IgE production
Asthma
A type I hypersensitivity reaction
Occurs when the allergic reaction is localised to the lungs
Leads to bronchial constriction
Type II hypersensitivity
Occurs when IgG (or IgM) antibodies are directed against self-cells
IgG binding causes opsonisation and complement fixation, leading to immune cell recruitment which damages the cells/tissue
Triggered by normally harmless foreign antigen
Goodpasture’s syndrome
A type II hypersensitivity response
Antibodies target the basement membrane in the lung or kidney
Linked to viral infections
Autoimmune haemolytic anaemia
A type II hypersensitivity response
Antibodies target native erythrocytes via blood group antigens
Leads to lysis of RBCs
Grave’s disease
A type II hypersensitivity response
Antibodies target the thymic stimulating hormone receptor
Leads to receptor activation and thyroid hormone synthesis
Myasthenia gravis
A type II hypersensitivity response
Antibodies block nicotinic acetylcholine receptors at the post-synaptic neuromuscular junction
Type III hypersensitivity
Occurs when IgG antibodies bind with soluble antigens
Self-antigens will be continually present so this leads to immune complexes becoming trapped in areas of the body
This activates immune cells, leading to tissue damage
Serum sickness
A type III hypersensitivity response
Triggered by injection of poorly catabolised foreign antigen
Results in deposition of immune complexes in blood vessels
Systemic lupus erythematosus
A type III hypersensitivity response
Occurs when antibodies target cytoplasmic antigens, leading to the deposition of immune complexes all over the body
Type IV hypersensitivity
Delayed & T-cell mediated
Granulomatous
A type IV hypersensitivity reaction
Granulomas form in response to persistent antigen and act to separate the antigen from the rest of the body
