Autoimmunity

Question 1

What is autoimmunity?

Answer 1

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

Question 2

What is the definition of autoimmune disease?

Answer 2

Disease caused by tissue damage or disturbed physiological responses due to autoimmune response

Question 3

What are some clinical patterns of autoimmune disease?

Answer 3

Organ specific;
One or multiple self antigens within one single organ or tissue

Non-organ specific;
Wide distributed self antigens throughout the body

Question 4

What is the criteria for diagnosis of an autoimmune disease?

Answer 4

1) Presence of autoantibodies/autoreactive T cells
2) Levels of autoantibodies correlate with severity of disease
3) Autoantibodies/autoreactive T cells present at site of damage
4) Transfer of autoantibodies/autoreactive T cells to healthy host inducing autoimmune disease
5) Clinical benefit provided by immunomodulatory therapy
6) Family history

Question 5

What are some types of autoantibodies involved in autoimmune diseases?

Answer 5

Primary autoantibodies:
Anti-TSHR, Graves’
Anti-ACh receptor, Myasthenia Gravis

Secondary autoantibodies:
Anti-nuclear, SLE
Anti-Rheumatoid factor, RA

Question 6

What are some maternal autoantibodies (IgG) that can be transferred during pregnancy?

Answer 6

RBCs => haemolytic anaemia => cell lysis

TSH receptor => neonatal Graves’

ACh receptor => neonatal Myasthenia Gravis

Nuclear antigen SSA/Ro => neonatal SLE

Question 7

What are some mechanisms of induction of autoimmunity?

Answer 7

Breakdown of central tolerance - fails to delete autoreactive T cells

Breakdown of peripheral tolerance - regulatory T cells defects, impaired immunomodulation, altered self antigens

Activation of autoreactive B cells - T cell independent activation of B cells

Question 8

What can trigger autoimmunity?

Answer 8

Genetics - increased risk w/ affected sibling
Environmental - hormones, infections, drugs
Infections

Question 9

What are some microbial infections leading to autoimmune diseases?

Answer 9

Streptococcus pyogenes M protein => antigen to cardiac muscle => Rheumatic fever

Campylobacter jejuni glycoproteins (food poisoning) => myelin associated ganglioside antigen => Guillian Barré syndrome