Autoimmunity

Question 1

What is autoimmunity?

Answer 1

Immune system can recognise between self and non self antigens and when this breaks down autoimmunity occurs.

We have auto reactive antibodies and auto reactive T cells which recognise normal components of the blood as foreign.

Certain HLA types can be predisposed to autoimmunity.

Question 2

Spectrum of autoimmunity

Answer 2

Can be organ-specific- hashimotos thyroiditis
Can involve many organs- systemic lupus erythematous- can cause an inflammation- can have symptoms on the face e.g. butterfly rash

Question 3

What are the pathological changes in hashimotos thyroditis?

Answer 3

In normal thyroid glands- we have acinar epithelial cells that secrete thyroid in the colloid spaces. In thyroiditis, the normal architecture is destroyed and there are replaced with macrophages, lymphocytes and plasma cells.

Question 4

Explain graves disease?

Answer 4

In a normal cell, the TSH binds to the receptor producing a stimulus to the thyroid cell to produce thyroid. However in graves disease, the autoantibody binds to the TSH receptor that continuously stimulates the thyroid cells to produce thyroid.

Question 5

Pernicious anaemia

Answer 5

Normally vitamin B12 is absorbed with an intrinsic factor- pernicious anaemia autoantibodies directed against IF are produced, binding to an IF which prevents B12 absorption.

Question 6

How can immunopathological damage occur with autoimmunity

Answer 6

A) When an auto antigen is localised to a particular organ, type 11 hypersensitivity reactions can occur which causes damage due to complement and phagocyte degranulation

B) Immune complexes appear to be pathogenic in systemic autoimmunity- type 111 hypersensitivity which causes acute tissue damage.

Question 7

What is sjogrens syndrome?

Answer 7

This is a chronic inflammatory autoimmune disorder- It is characterised by a lymphocytic infiltrate in salivary and lacrimal glands which causes slow destruction and replacement of glandular tissue -> fibrous tissue

This causes a lack of tear and lack of saliva that causes dental caries or oral candida.

Symptoms include- dry lips, lobulated tongue, caries

Question 8

What is the treatment of autoimmune disorder?

Answer 8

1) metabolic control in some conditions (injection of B12 in anaemia, anti-thyroid drugs in graves disease)
2) Anti-inflammatory drugs e.g. corticosteroid
3) immunosuppressive drugs
4) Monoclonal antibodies to blockade certain cytokines or their receptors-

infliximab- blocks the action of tumour necrosis factor- it inhibits the immune response by binding certain cytokine.