Hypersensitivity Flashcards
1
Q
Type I Hypersensitivity
A
ALLERGIC TYPE HYPERSENSITIVITY
- Generated in response to a foreign innocuous particle
- Individuals must be sensitised at first before allergy is prompted
- Ag:Ig crosslinking causes immune stimulation
- IgE, bound to the surface of mast cells binds particles stimulating mast cell degranulation and subsequent secretion of histamine. Vasodilation and permeability follow, leading to inflammation.
- Th2 response.
- Example: Asthma
2
Q
Type II Hypersensitivity
A
ANTIBODY MEDIATED HYPERSENSITIVITY - ANTIBODY DEPENDENT CELLULAR TOXICITY (ADCC)
- IgG, IgM and some IgA
- Antibodies bind to the basement membrane of cells, allowing complement binding (C1q), MAC formation and cell membrane damage follow OR through binding of cytotoxic cells (NK cells)
- Can be directed against foreign particles or in response to self
- Sensitisation
- Example: Rhesus haemolytic disease of the new born
3
Q
Type III Hypersensitivity
A
ANTIBODY COMPLEX HYPERSENSITIVITY
- Antibody complexes are normally cleared by the liver or spleen (bind to RBCs). However, constant activation can lead to an accumulation of the complexes.
- Ag:Ig complexes are deposited in various tissues types
- The complexes are then able to bind the surface of cells and prompt the complement cascade, cell damage follows.
- Example: Persistent infection, autoimmunity or inhaled antigen
4
Q
Type IV Hypersensitivity
A
DELAYED TYPE HYPERSENSIVITITY (12h) - TH1
- Th1 stimulation leads to the production of macrophage stimulation cytokines, e.g. IFN-gamma.
- Constant stimulation of macrophages leads to the formation of a giant nucleate cell
- Requires sensitisation to occur
- Example: Contact dermatitis, TB
5
Q
Normal activation of mast cells
A
Through binding of complement proteins C3a and C5a via CRs
Through binding of epitopes via their sIgE
