General - hypersensitivity

Question 1

1) What is the mechanism of type I hypersensitivity reaction
2) Give an example of type I hypersensitivity reaction

Answer 1

1) Antigen reacts to IgE that’s bound to mast cells
2) Anaphylaxis, atopy i.e. asthma, eczema

Question 2

1) What is the mechanism of type II hypersensitivity reaction
2) Give an example of type II hypersensitivity reaction

Answer 2

1) IgG or IgM binds to antigen on cell surface
2) Autoimmune haemolytic anaemia, idiopathic thrombocytopenic purpura, anti GBM disease, pernicious anaemia, rheumatic fever

Question 3

1) What is the mechanism of type III
hypersensitivity reaction
2) Give an example of type III hypersensitivity reaction

Answer 3

1) Free antigen and antibody combine (IgG and IgA) - immune complex
2) Post streptococcal GN, extrinsic allergic alveolitis, SLE, serum sickness

Question 4

1) What is the mechanism of type IV hypersensitivity reaction
2) Give an example of type IV hypersensitivity reaction

Answer 4

1) T cell mediated
2) GBS, MS, TB, graft vs host disease, scabies, allergic contact dermatitis