Introdcution

Question 1

what is the name of naive t cells

Answer 1

thymocytes

Question 2

where do progenitor T cells develop

Answer 2

the thymus, after being formed in the bone marrow

Question 3

describe the process of T cell development in relation to the T cell receptor

Answer 3

1. thymocytes enter the thymus from bone marrow as double negative cells
2. they begin differentiation programme from DM1 to DM4 to to produce the T cell receptor through DNA recombination
3. cells which produce a receptor are given a signal to replicate, those which do not are killed through neglect.
4. as development continues they express CD4 and CD8 to become double positive cells
5. the cells then under education process which involves 2 aspects- positive selection for those which can see MHC followed by negative selection for those which see MHC too well. This is mediated by dendritic cells which test the affinity of the interaction.

Question 4

how does the immune system get around the issue that during thymocyte education process they may not be exposed to proteins which are only expressed in certain parts of the body and therefore may elicit an autoimmune response

Answer 4

dendritic cells contain AIRE, an autoimmune regulator, which up regulates proteins that wouldn’t usually be found in the thymus. This is called central tolerance.

Question 5

which cells present MHC II molecules to T cells

Answer 5

dendritic cells, macrophages and B cells

Question 6

how does stimulation of T cells occur

Answer 6

APCs travel to secondary lymphoid organs after phagocytosis of pathogen to present antigen and deliver co-stimulatory signal (signal 2)

Question 7

summarise the cellular immune response

Answer 7

cytotoxic t cells bind to MHCI presenting cells and elicit cytotoxic response against intracellular pathogens and tumourgenic cells

Question 8

summarise the humoural response

Answer 8

B cells produce antibodies which bind to antigens in extracellular environments. they neutralise, opsonise and activate complement

Question 9

what are the causes of SCID

Answer 9

deficient in T and B cells. abnormalities occur in receptors particularly IL2. this prevents T cells from proliferating. also deficiencies in ADA enzyme prevent them undergoing education process and thus maturation