T Cell Essay Flashcards
What are T cells involved in?
Cellular responses to intracellular pathogens such as virus’ and regulation of B cells
What are the 4 groups of R cells ?
Th1,
Th2
Cytotoxic T cells
Regulatory T cells
How come T cells can’t recognise antigens in native form?
They must be presented with an antigen which has been processed and bound to HMC
How are MHC 1 molecules expressed ?
Found and expressed on the surface of uncleated cells in the body
How are MHC 11 molecules expressed ?
Found and expressed on antigen presenting cells
What are T cells developed from?
Haemopoetic stem cells
Where are they produced ? And as what?
Bone marrow
Double negative thymocytes
Where do they migrate too?
Thymus for further development
What happens in gene rearrangement in T cells ?
VDJ rearranged which encode variable region
What happens to genes encoding TCR a&B?
Expressed at low density on cell surface and randomly switch segments of their genes to create diversity to recognise a variety of antigens
What is the process mediated by ?
Rag1/2
What is the first gene to rearrange ?
TCR b chain and if the cell doesn’t make this chain it dies
What does successful rearrangement indicate ?
Prevent cell from creating further rearrangement and to express both CD4&CD8
What is the thymocytes considered now ?
Double positive
What does this signal the cell to do?
Start rearrangement on the TCR a chain
What does successful rearrangement allow ?
Binding to the B chain
Where does positive selection occur ?
Cortex of thymus
What do they encounter ?
Cortical epithelial cells
What do CEC do?
Express both classes of MHC on their surface and only thymocytes that can bind to either class receive a survival signal
What do thymocytes which bind to MHC class I become ?
CD8 due to loosing CD4 expression
What do thymocytes which bind to MHC class II become ?
CD4 due to loosing CD8 expression
Where does negative selection occur ?
Corticomedullary junction
What happens ?
Thymocytes which bind too strong to MHC derived from self antigens receive the death signal
When do cell leave the thymus and as what?
Following selection process as mature T cells
