Hypersensitivity and autoimmunity Flashcards
What are type I,II and II mediated by?
Antibodies
What is type 4 caused by?
Inappropriate Th1 cell action
What is type 1 sensitivity also known as?
Allergy
How does type 1 principally arise?
Inappropriate IgE synthesis
In type 1 what id the IgE directed towards?
Antigens that may be airborne, ingested, skin contact or injected
What do the allergic problem arise from?
Genetic factors
Environmental factors
Hormonal and neurological influences
Immune regulatory factors
Atopy
A state of sub-clinical immune sensitisation
What are type 1 allergic reaction mediators?
Histamine
Mucosal oedema
Vasodilation
What is type 2 hypersensitivity mediated by?
IgG or IgM antibodies directed against antigens found on the surface of cells or fixed within certain tissues
What can the antigens be?
Exogenous or derived from self
What happens in type 2?
Complement activation stimulate phagocyte
Inhibit function
How do clinical conditions in type 3 arise?
Abnormal deposition of formed antigen or antibody in tissues
Pathological immune complex inflammation
Deposited in many tissues - serum sickness
Complexes formed locally in tissues - arthus reaction
Why do type 4 reactions occur?
Immune system finds it difficult to destroy these environmental agents
What are type 4 mediated by?
Cytokines products eg interleukin-2 and interferon
Th1 cells
