adaptive immune system (T cells) Flashcards
what are the 3 types of T cell
T helper celler
T killer cell
T regulatory cells
what is the defining receptor for t cells
the T cell receptor (TCR). it is important in recognising antigens
what receptors define each class of T cell
T helper cells: CD4
T killer cells: CD8
T regulatory cells: CD4+CD25
what are the key functions of a T helper cell
T helper cells secrete cytokines to communicate to other immune cells.
The two most important cells they secrete are interleukin 2 and Interferon gamma
what are the key functions of a T killer cell
they make contact with targeted cells and causes them to trigger apoptosis.
they are potent enough to kill any bacteria or viruses inside the cell.
They are also important for tumour defence
what are the roles of T regulatory cells
control the immune system and make sure the reaction is too strong and potentially dangerous.
Help prevent autoimmune diseases
how do T cells detect pathogens when B cells can not
B cells can only interact with pathogens directly such as with cell surface receptors or antibodies. this is not effective when a pathogen invades another cell and its antigens are hidden fro view.
T cells can interact with the MHC1 to recognise any protein within the cell including foreign ones.
how does the MHC1 complex work?
-proteins within the cell are degraded by the enzyme proteasome
-the degraded peptides are taken to the ER and bind to MHC1 proteins
-the complex is then transported to the cells surface
-T killer cells then analyse the complex with their CD8 and TCR receptor to decide wether the peptide fragment is foreign or not
how does the MHC2 complex get recognised
T cells with the CD4 receptor (helper and regulatory T cells) use that and their TCR to analyse the MH2 complex
explain the process of immune tolerance
-immature T cells travel from the bone marrow to the thymus
-here they express low levels of TCR, both CD4 and CD8 (double positive)
-these double positive cells are very unstable with low levels of Bcl2
-next they undergo positive selection where cortical epithelial cells test to see if they can recognise a MHC1 complex
-next they undergo negative selection where dendritic cells test to see if they recognise self proteins being presented by an MHC1 complex
-T cells that pass this test will then take 2 weeks to expresses either CD4 or CD8 and become a functioning T cell
how do macrophages interact with T cells
since macrophages are too big to travel they can’t train T cells in lymph nodes like dendritic cells can.
instead they act as refusing stations. T cells need to be constantly re stimulated by MHC2 complexes or else they think the infection is gone
what are the 3 subsets of T helper cell and what do they do
Th1: coordinates response against intracellular pathogens
Th2: coordinates response against parasites
Th17: coordinates response against fungi and bacteria
what is CAR-T
Chimeric Antigen response T-cells are cutting edge cancer treatment. they allow for custom cytotoxic T cells which can target tumour cells. These are highly effective, but very expensive.
