028 Immunological tolerance

Question 1

Why doesnt the body’s own cells trigger complement system?

Answer 1

Because they contain complement inhibiting receptors

Question 2

Describe B cell selection

Answer 2

B cells in the bone marrow are presented with self antigens. If they recognise these antigens, then it will either change its specificity, or it will become aptotic

Question 3

Describe T cell selection

Answer 3

T cells will migrate to the thymus for maturation. At first, they are double negative. Then they undergo gene arrangement and become double positive. One of the genes is then switched off. The T cells first undergo positive selection, in which thymic epithelial cells will present self MHC Class I and Class II. If T cells recognise the MHC cells, then they will be rescued, whilst those that dont become apoptotic by neglect. T cells then undero negative selection, in which if it recognises the MHC too strongly (without a peptide, or with self peptide), then it will become apoptotic.

Question 4

What is transcription factor AIRE

Answer 4

This is the gene that allows self MHC to be expressed on thymus when it should normally be on other cells.

Question 5

Where does peripheral tolerance take place and what is its function?

Answer 5

It occurs in the lymph nodes, spleen, or mucosal and cutaneous tissue.

Question 6

What are the 4 different cell intrinsic mechanisms of peripheral tolerance?

Answer 6

Anergy - does not have the coreceptor because the cell is resting
Ignorance- never sees its antigen
Phenotypic skewing - cannot function properly
Aptosis - cells are programmed to die by Fas receptor

Question 7

What is found on the surface of Treg?

Answer 7

CD25, regulated by FOXP3

Question 8

How do Treg cells work to modify APC?

Answer 8

Blocking or removing co-stimulatory ligands by CTLA-4