Autoimmune diseases:

A) Organ-specific (Immune response directed against localised antigens)

1. Grave’s disease.
2. Hashimoto’s thyroiditis.
3. Addison’s disease.
4. Pernicious anaemia.
5. Type 1 diabetes
6. Sympathetic ophthalmoplegia.
7. Goodpasture’s syndrome.
8. Pemphigus vulgaris.
9. Bullous pemphigoid.
10. Idiopathic thrombocytopenic purpura.
11. Autoimmune haemolytic anaemia.
12. Myasthenia gravis.
13. Rheumatoid arthritis.
14. Dermatomyositis.
15. Primary biliary cirrhosis.
16. Autoimmune hepatitis.
17. Sjögren’s syndrome.

B) Multisystem (Immune response directed to widespread target antigens):

1. Systemic sclerosis.
2. Mixed connective tissue disease.
3. SLE

Factors predisposing to autoimmune disease:

Multiple genetic and environmental factors-

• Female sex.
• Association with HLA
• Infection.
• Cigarette smoking
• Hormone levels.
• Adverse effects of drug treatment.

Mechanism of autoimmune disease : 

Mechanism/causes of autoimmunity:

1) .  Loss of self-tolerance: It may happen when there is defect in the following processes of self tolerance-

• Self-reactive T-lymphocytes are deleted in the thymus.
• Self-reactive T-cells may be deleted in the periphery.
• Self-reacting T-cells may be hypofunctioning or non-functioning in the periphery.
• Escape of tolerance at B-cell level.

2) Cross reactivity:

• Immune response against a self-antigen by virtue of a similar structures of the foreign and self antigens.

3) Molecular mimicry:

• There is identical sequences of amino acids between many foreign antigens and self antigens. e.g.  retroviral proteins. The situation is called molecular mimicry. 

4) Idiotypic interactions:

• Idiotype constitutes a normal self-interaction.

5) Super antigens:

Antigens that are able to interact with all of the T cells bearing a particular ẞ chain outside the normal antigenic groove are called super antigens. Such antigens may give rise to autoimmune phenomenon e.g. Staphylococcus aureus toxin is responsible for Toxic shock syndrome.

6) Alteration of normal proteins: Drugs can bind to normal proteins and make them immunogenic. Procainamide induced systemic lupus erythematosus is an example of this mechanism.

7) Release of sequestered antigens: Certain tissues (e.g, sperm, central nervous system, and the lens and uveal tract of the eye) are sequestered so that their antigens are not exposed to the immune system These are known as immunologically privileged sites. When such antigens enter the circulation accidentally (e.g, after damage), they elicit both humoral and cellular responses, producing aspermatogenesis, encephalitis, or endophthalmitis, respectively.

8) Epitope spreading: Epitope spreading is the term used to describe the new exposure of sequestered autoantigens as a result of damage to cells caused by viral infection. These newly exposed autoantigens stimulate autoreactive T cells, and autoimmune disease results.