Category:Autoimmune Diseases

Antibody mediated autoimmune diseases

Myasthenia gravis

1. Immune Mediated Haemolytic Anaemia (IMHA)

Pathogenesis: Type II hypersensitivity

• Autoantibody attack on the red blood cells causing extravascular and intravascular lysis which causes anaemia.
• The in saline autoagglutination test and the coombes test is used to diagnose the disorder.

2. Immune Mediated Thrombocytopaenia (IMTP)

Pathogenesis: Type II hypersensitivity

• There is an immunological attack on the platelets which reduces the ability for clotting.
• A reduced platelet count and detection of anti-platelet antibodies in the serum are used for diagnosis of this disorder.

3. Myasthenia gravis

Pathogenesis: Type II hypersensitivity

4. Bullous Pemphigoid

Pathogenesis: Type II hypersensitivity

5. Pemphigus Vulgaris

Pathogenesis: Type II hypersensitivity

6. Systemic Lupus Erythematosus (SLE)/Multi-systemic immune mediated disease

Pathogenesis: Type III hypersensitivity

Cell mediated autoimmune diseases

Rheumatoid Arthritis-Brian Catchpole RVC 2008

Diabetes Mellitus-Brian Catchpole RVC 2008

1. Rheumatoid arthritis

Pathogenesis:

• Type IV hypersensitivity: CD4 Th-1 cell mediated.
• Macrophages phagocytose self antigens and can present peptides on their MHC Class II molecules. The autoreactive TH-1 cells release IFN-gamma which activates macrophages to release prostaglandins, MMP enzymes and TNF-alpha (pro-inflammatory mediator), see diagram. These cytokines cause inflammation and tissue destruction.

2. Diabetes Mellitus type I

Pathogenesis:

• Type IV hypersensitivity
• The CTLs think that all the beta cells in the pancreas are infected by a virus, as it wrongly detects a self antigen presented by the MHC class I on the surface of the cell as foreign.
• Autoreactive CD8+ CTLs are inadvertently activated, destroying the beta cells, thus preventing the secretion of insulin and causing diabetes type 1 (see diagram).

3. Hypothyroidism (lymphocytic throiditis)

Pathogenesis: Type IV hypersensitivity

• T cell mediated

4. Hypoadrenocorticism (Addisons disease)

Pathogenesis: Type IV hypersensitivity