Hypersensitivity & Autoimmunity Flashcards
Define Hypersensitivity
Disorders where normally beenficial parts of an immune response act in an exaggerated or innapropriate fashion to enviromental antigens and cause tissue damage. (bystander damage)
Which types of hypersensitivity are mediated by antibodies?
Types I, II & III
What causes type IV hypersensitivity?
Innapropriate action of Th1 cells.
What is type 1 hypersensitivity also called?
“allergy”
How does Type 1 hypersensitivity arise?
enviromental antigens (allergens) are mistaken for pathogens & IgE is innapropriately synthesised.
What does the allergen-specific IgE released during type 1 hypersensitivity do?
It trigers mast cells to release inflammatory mediators like histamine & prostoglandins.
What are the consequences of type 1 hypersensitivity?
Mucosal Oedema Capillarly leakage vasodilation ETC (basically inflammation
What factors influence allergic problems? (think what factors all immune responses arise from)
- Genetic factors
- Hormonal & neurological influences
- Enviromental Influences
- Immune regulatory factors
Why isnt the prescnce of IgE alone enough for an alleric reaction to occur?
A clinical allergy arises through many factors not just immune regulatory factors so IgE can be associated with symptoms or not.
What is it called when IgE is present but no smptoms occur?
Atopy
A state of sub-clinical immune sensitisation
What antibodies mediate Type 2 hypersensitivity?
IgG & IgM antibodies
Why is the line between type 2 hypersensitivy & autoimmune blurreD?
Because in type 2 the IgG & IgM antibodies can bind to exogenous or self antigens.
How does type 2 hypersensitivity occur?
- IgG & IgM antibodies target antigens on the surface of cells or within tissues.
- They cause tissue damage
How do antibodies in type 2 hype cause tissue damage?
- complement activation triggers cell lysis
- Fc receptors on phagocytes bind to immunoglobulin & phagocytic activity is stimulated
- antibody dependant cellular cytotoxicity (ADCC)
- inhibit/stimulate cell function
What is immune complex formation?
antigens & antibodies from complexes together.
They are normally transported to the liver/spleen where theyre destroyed by phagoctytes.
How does type 3 hypersensitivity occu?R
Predisposing factors in the Ag or the Ab cause the immune complex to precipitate into tissues & cause inflammation