Hypersensitivity reaction

과민 반응(Hypersensitivity reaction, Hypersensitivity types)은 면역 체계에 의한 원치 않는 반응으로 기전에 따라 크게 4가지로 분류한다. .

분류

Type 1 hypersensitivity

• Type I Immediate type hypersensitivity( IgE depedent or anaphylactic)
  • ex) Allergic rhnitis, asthma, systemic anaphylaxis, Drug allergies(penicillin, insulin, cephalosporin)

Type 2 hypersensitivity

• Type IIa Cytotoxic or cytolytic reactions
  • ex) Drug allergies(penicillin)
• Type IIb Cell stimulating reactions involving altered cell function
  • ex) Chronic urticaria

Type 3 hypersensitivity

• Type III Antigen-antibody complex(immune complex) hypersensitivity reaction
  • ex) Serum sickness, PSGN, SLE, Arthus reaction

Type 4 hypersensitivity

Delayed type hypersensitivity로 sensitized T lymphocyte가 Ag을 만나 cytokine 분비 및 macrophage 활성화

• Type IVa1 Classical delayed type
  • ex) Contact dermatitis, tuberculin reaction(tuberculin skin test)
• Type IVa2 Cell mediated eosinophlic(or Chronic allergic inflammation
  • ex) Chronic asthma, chronic allergic rhinitis
• Type IVb Tissue injury by cytotoxic T cell
  • ex) contact dermatitis

IgE Ab crosslink에 의한 mast cell 활성화 기전

1. Allergen cross linkage of cell-bound IgE
2. Antibody cross-linkage of IgE
3. chemical cross linkage of IgE
4. cross-linkage of IgE receptors by anti-receptor antibody
5. enchanced Ca2+ influx by ionophore that increases membrane permeability to Ca2+

호산구의 Toxic protein

• MBP(Major basic protein)
• ECP(Eosinophil cationic protein)
• EDN(Eosinophil-derived neurotoxin)