Autoimmunity

Question 1

Define autoimmunity

Answer 1

Immune response against the host due to loss of immunological tolerance of self-antigens

Question 2

Define autoimmune disease

Answer 2

Disease caused by tissue damage/disturbed physiological responses to an autoimmune response

Question 3

What are the criteria for a disease to be considered autoimmune?

Answer 3

Presence of autoantibodies/autoreactive T cells
Levels of autoantibodies correlate with disease severity
Autoantibodies/autoreactive T cells found at the site of tissue damage
Transfer of autoantibodies/autoreactive T cells to healthy host induces autoimmune disease
Family history
Clinical benefit from immunomodulatory therapy

Question 4

How does tissue damage occur in autoimmunity?

Answer 4

Autoantibodies - complement activation, antibody mediated cell cytotoxicity, neutrophil activation
Autoreactive T cells - Cytotoxic T cells, macrophages

Question 5

Explain how infection can lead to autoimmunity

Answer 5

Streptococcus pyogenes produces an antigen that is similar to cardiac muscle antigen, body produces antibodies that cross react causing rheumatic fever that damages the heart

Question 6

Which drugs can induce autoimmunity?

Answer 6

Methyl-dopa (antihypertensive) - haemolytic anaemia

Procainamide (antiarrythmic) - SLE

Question 7

Describe the endogenous ways that autoimmunity can be induced

Answer 7

Failure to delete autoreactive T cells - breakdown of central tolerance
Altered self antigens and T cell defects - breakdown of peripheral tolerance
Independent activation of B cells (without T cells) - activation of autoreactive B cells

Question 8

What are the strategies for treating autoimmune diseases?

Answer 8

Plasma exchange
Immunosuppressive drugs
Anti-inflammatory drugs
Monoclonal antibodies (Infliximab)

Question 9

How does neonatal myasthenia gravis occur?

Answer 9

Maternal IgG antibody to acetylcholine receptor causes a receptor blockade, causing skeletal muscle weakness

Question 10

How does neonatal Grave’s disease occur?

Answer 10

Maternal IgG antibody to thyroid stimulating hormone causes activation of the fetus’ TSH receptors, causing hyperthyroidism

Question 11

How does autoimmunity cause congenital heart block?

Answer 11

Maternal IgG antibody to nuclear antigen Ro causes neonatal SLE, resulting in congenital heart block