Antigen recognition (7) Flashcards
What are T lymphocyte receptors not expressed as?
Soluble proteins?
What is T cell immunity important in defence against?
Intracellular pathogens
What are T cytotoxic cells also known as?
CD8 +ve
What are T helped cells also known as?
CD4+ ve
What do T cytotoxic cells do?
Specifically kill infected host cells
What do T helper cells do?
Augment immune responses
What is B cell immunity particularly important in?
Defence against extracellular pathogens.
What do B cells recognize?
Soluable, free native antigens.
What do T cells regcognize?
Cell associated pathogens.
What MHC class is expressed by all nucleated cells?
Class I
What MHC class is expressed by certain leucocytes?
Class II
What Leucocytes express MHCII?
Dendritic cells, B cells and macrophages.
What do MHC class 1 do?
Present peptides from endogenous proteins.
What do MHCII do?
Present peptides from exogenous proteins.
What type of cell recognises peptides bound to MHC1?
Cytotoxic T cells.
How do cells present peptides for cytotoxic T cells?
A virally infected cell produces viral proteins. These are broken down in the cytosol and the peptides are transported to the ER. Here they bind to the MHCI and are taken to the cell surface.
What type of cell recognises proteins bound to MHCII?
Helper T cells.
How do cells present peptides for T helper cells?
The antigen presenting cell internalises and breaks down foreign material. The peptide is then bound to MHCII in the endosomes which takes the proteins to the cell surface.
What receptor has a Fab like structure?
The TCR.
What domains of the TCR are homologous to the V and C regions of the immunogloblins?
Extracelluar domains.
What two chains make up the TCR?
Alpha and beta.
How big is the TCR?
43 kD.
What percentage of T cells express gamma/delta receptor?
1-5%
Where are T cells that express gamma/delta found?
Epithelial surfaces.
T cells that express gamma/delta receptors are less diverse. What is the consequence of this?
They recognise a broader range of antigens.
What complex do TCR’s recognise?
Antigen + self MHC.
What region of the alpha and beta chains are most variable?
CDR3.
Crystallographic studies of TCR showed that CDR1 and CDR2 bind what?
Self MHC.
Crystallographic studies of TCR showed that CDR3 bind what?
Foreign peptides.
What forms the TCR complex?
TCR receptor, CD3 subunit (x2), signal transduction.