Information about different types of Hypersensitivity

Types of Hypersensitivity

Type I

• It is immediate type of Hypersensitivity
• Immune reactant is IgE
• Antigen form is Soluble antigen
• Initiation time is 2-30 minutes
• Mechanism of activation: Allergen- specific IgE Ab Bind to mast cells via their Fc receptor. When specific allergen bind to IgE, cross linking of IgE induces degranulation of mast cells
• Example;
  • Food allergies like;
  • peanuts
  • egg
  • fish

Type II

• Immune reactant is IgG or IgM
• Antigen form is Cell bound antigen
• Initiation time is 5-8 hours
• Mechanism of activation: IgG or IgM Ab Bind to cellular antigen, leading to compliment activation and cell lysis. IgG also mediate ADCC with cytotoxic T cells, NK cells, macrophage and neutrophils
• Example;
  • Erythroblastosis foetalis

Type III

• Immune reactant is IgG or IgM
• Antigen form is Soluble antigen
• Initiation time is 2-8 hours
• Mechanism of activation: Ag – Ab Complexes are deposited in tissues. Compliment activation provides inflammatory mediators and recruits neutrophils. Enzymes released from neutrophils damage tissue
• Example;
  • Arthus reaction,
  • Serum Sickness,
  • Blue eye condition in dog

Type IV

• It is Delayed Type Hypersensitivity
• Immune reactant is T-cell
• Antigen form is Soluble or cell bound antigen
• Initiation time is 24-72 hours
• Mechanism of activation: TH₁ cells secrete cytokines, which activate macrophage and cytotoxic T cells
• Examples;
  • Tuberculin test (Diagnosis of tuberculosis)
  • Johnin test (Diagnosis of Johnes disease)
  • Mallein test (Diagnosis of glander)
  • Brucellin test (Diagnosis of Brucellosis)
  • Mantoux test (Diagnosis of tuberculosis)

Download the image from attachments.