Autoimmune diseases

Autoimmune diseases

1. Caused by: failure in self-tolerance, multigenic disorders or the environment

   • Leads to immune system attacks on the body
   • Similar classifications to hypersensitivity types

2. Type 2

   • E.g. Myasthenia gravis
     • an autoantibody against the ACh receptor leads to their destruction, causing fatigue, muscle weakness and drooping eyelids
   • E.g. Grave's disease
     • there is an autoantibody for thyroid stimulating hormone receptors and so the hormone thyroxin is always produced, leading to hyperthyroidism
       • Symptoms include nervousness, tremor, bulging eyes and weight loss, as thyroxin is the body’s “accelerator”

3. Type 3

   • E.g. Systemic Erythemous Lupus
     • antibodies against nucleic acids and phospholipids are present
     • “butterfly rash”, pericarditis and arthritis

4. Type 4

   • E.g. Type 1 Diabetes Mellitus
     • T cell reactions to pancreatic β cells, which produce insulin
   • E.g. MS
     • Demyelinating disease, where nervous insulation is attacked
   • E.g. Chronic inflammatory bowel diseases: Ulcerative colitis and Crohn’s disease
   • E.g. Rheumatoid arthritis

5. Type 1?

   • infection by a common antigen causes upregulation of APC co-stimulators and so a greater immune response
   • Infectious agents can instigate an immune response against host self cells by
     • Modification
     • Inflammation
     • Molecular mimicry
     • T cell tolerance is bypassed