T Cells Flashcards
Where are T cells made?
bone marrow
Where do T cells mature?
the thymus
What 2 responsibilities do T cells have?
cell mediated immunity
assisting B cells
What cell surface receptor do T cells have?
T Cell Receptor
How are T Cells able to recognise antibodies?
only when they are bound to MHC
What T cells stimulate B cells to produce antibody?
Helper or CD4+
What T cells are cytotoxic?
CD8+
How do B cells recognise free organic antigen?
via B Cell Receptors that bind the antigen
How do T cells recognise antigen?
only when they are in a complex with a MHC
CD4+ and helper cells recognise MHC2
CD8+ recognise MHC1
What are the 2 criteria for the successful maturation of T cells?
- must learn to not recognise our own ‘self’ antigens
- must be restricted to recognising antigen only when it is in association with our own MHC
What is meant by ‘positive selection’ of T cells?
Immature T cells in the thymus that are just starting to present TCR and CD4+ and CD8+ are presented with self MHC on epithelial cells.
Those that recognise it, live. Those that do not, die.
What is meant by ‘negative selection’ of T cells?
The immature T cells are presented MHC in association with self antigen. The cells that bind strongly to these complexes of MHC and self antigen, die.
Where is MHC Class 1 found?
on virtually all nucleated cells
What does MHC Class 1 do?
presents ‘virally induced’ peptides to CD8+ cells and trigger cytotoxic response
Where is MHC Class 2 found?
only on antigen presenting cells
What does MHC Class 2 do?
- presents antigen to CD4+ T cells
- activate macrophages and B cells
What do T helper cells do? (3 things)
- activate and direct other immune cells
- essential in B cell antibody switching
- essential in activation and growth of cytotoxic T cells
What chemical do cytotoxic T cells release when exposed to infected/ dysfunctional somatic cells?
perforin
What does perforin do?
forms pores in the target cell
What happens once the pores are formed in the target cells?
the cytotoxic T cells also release Granzyme B which is a protease and enters via the pore and induces apoptosis
What can memory T cells arise from?
- from fully differentiated T cells
- from partially differentiated T cells allowing for further differentiation on re-exposure to the antigen
