Hypersensitivity

Question 1

Type I (what it is and test)

Answer 1

Anaphylactic: Ag crosslinks IgE on presensitized mast cells/basophils causing histamine release and all that shit. Delayed response due to production of arachidonic acid metabolites (e.g. leukotrienes)
Test with skin test for specific IgE - “wheel and flare” reaction with defined borders in about 15 minutes

Question 2

Type II Hypersensitivity (what it is and test)

Answer 2

Abs against self cause the problem, leading to complement, macs, Nks, etc
Coombs test

Question 3

Type III Hypersensitivity

Answer 3

ICs form and cause the problems, recruiting neutrophils which can cause destruction. Can be anti-self Abs, but the ICs actually the problem

Question 4

2 Type III Hypersensitivity Special Reactions

Answer 4

Serum sickness - Abs form to foreign proteins (usually drugs) and deposit in like five days, leading to complement and tissue damage
Arthus reaction - local subacute antibody-mediated hypersensitivity reaction. Intradermal injection of Ags induces ICs in skin, leading to edema, necrosis (from thrombosis), and complement activation

Question 5

Type IV Hypersensitivity

Answer 5

Delayed, T cell mediated releasing cytokines and activating macs (like contact dermatitis, graft v host, MS, PPD