Hypersensitivity Flashcards
Type I hypersensitivity
IgE mediated
- Allergy
- Does not involves complement
- Immediate response within minutes
- Has 2 phases
- Response may be to food, pollen, dust, chemicals
- e.g. Anaphylaxis, atopic dermatitis
Type II hypersensitivity
Antibody-mediated cytotoxic reaction
- Usually IgG mediated (IgM possible)
- Reaction maximal within 5-10 hrs
- Antibody recognises molecule/antigen on host cell or tissue
- Sources of these antigens/molecules can be intrinsic or extrinsic
- e.g. Intrinsic: body’s own blood cells (haemolytic anaemia)
- e.g. Extrinsic: drug metabolite
- Cells can be destroyed by complement, phagocytosed by innate immune cells, or by toxins from NK cells
Type III hypersensitivity
Immune complex mediated
- IgG/immune complex mediated
- Reaction maximal at 4-8 hrs
- Antibody/antigen complexes escape the normal route of clearance (i.e. phagocytosis)
- e.g. Equine Recurrent Airway Obstruction (RAO)
Type IV hypersensitivity
Delayed type hypersensitivity
- T cell mediated;
- Involves primed (memory) T cells and also macrophages/dendritic cells
- Reaction maximal at 24-72 hrs
- T cells recruit and activate mononuclear cells e.g. monocytes, tissue macrophages
- Inflammation at the site of the DC/T cell interaction occurs
- e.g. Johne’s disease
Which type of hypersensitivity is shown here?
Type III - immune complex mediated
Which type of hypersensitivity is shown here?
Type IV
Why is the reaction maximal of Type I hypersensitivity shorter than that of other hypersensitivity reactions?
Type I only involves IgE-mediated effects rather than activation of the complement system.
Outline how Type II and III hypersensitivity differs
- Both Type II and Type III can be IgG mediated
- Type II involves IgG and IgM directed against cellular antigens/molecules → leads to cell damage mediated by other immune system effectors
- Type III reactions involve IgG, IgM and occasionally IgA1 antibodies forming immune complexes
Outline the difference between cell mediated and antibody mediated hypersensitivity
- Type I, II and III hypersensitivity reactions are antibody mediated, whilst Type IV is cell-mediated.
- Cell mediated reactions take longer than antibody-mediated responses because they take longer for cells to be recruited to the site of exposure.
Outline how the antigens involved in Type II and Type III hypersensitivity differ?
- Type II = antigens are bound to cell surface
- Type III = antigens are soluble
Which condition is pictured here and which type of sensitivity is it?
Myasthenia gravis
Type II hypersensitivity
What structure is shown here? Which disease could it be associated with? What type of hypersensitivity is this?
Granuloma
Bovine TB
Type IV
What condition is shown here? What type of hypersensitivity is it?
Canine blue eye
Associated with canine adenovirus
Type III hypersensitivity
Give some examples of Type I hypersensitivity
- Anaphylaxis
- Atopic dermatitis
- Asthma
- Allergic rhinitis
True/false: you can be genetically susceptible to hypersensitivity
True
e.g. could have high levels of circulating IgE or specific MHC genes
