Type II Hypersensitivity

IMMUNOLOGY HYPERSENSITIVITY

Type II Hypersensitivity-Brian Catchpole RVC 2008

Introduction

Production of IgM or IgG to cell surface antigens or extracellular matrix proteins.

Mechanism

"Neutralisation" blockade of receptors:

• Antibodies attach to receptors which prevents other molecules attaching.
• For example in myasthenia gravis antibodies attach to acetylcholine receptors which in turn prevents acetylcholine from attaching to the receptor and thus muscle contraction of that cell does not occur.

Immunological attack on target cells, destroying them by (see diagram):

1. Antibody dependent cell cytotoxicity (ADCC)

• Pemphigus vulgaris
• Bullous pemphigoid

2. Complement mediated lysis

• Self RBC antigen:
  • Immune mediated haemolytic anaemia
• Foreign RBC:
  • Blood transfusion reaction
  • Haemolytic disease of new born (Rhesus disease in humans and neonatal isoerythrolysis in foals and kittens)
• RBC parasite:
  • Feline infectious anaemia (Mycoplasma haemofelis)

3. Phagocytosis