T-cells Flashcards
What is the most variable region on TCRs?
Where D and J segements join
Why is where D and J join the most diverse?
Due to junctional diversity - extra nucleotides added to the region
Whats an MHC?
Major histocompatibility complex
What are MHC molecules?
Molecules that bind to proteins from viruses and bacteria- then presents them to the T-cell ( called antigen presentation)
How many classes if MHC are there?
2
What are MHC class 1?
MHC molecules found on most nucleated cells- present antigens to cutotoxic T-cells
What are MHC class 2?
MHC molecules found on antigen presenting cells presents antigen to helper T-cells
What does it mean MHC genes being highly polymorphic mean?
High amoint of genetic diversity
What is an APC?
Antigen presenting cell
What are 3 types of APCs?
Dendritic cells
Activated macrophages
Activated B-cells
How are T-cells activated?
Dendritic cells take up pathogens and bring them to the lymphnode they interact wirh niave T-cell activating them into helper and cytotoxic T-cells
What are CD4 T-cells for?
They release cytokines that stimulate macrophages and CD8 T-cells
What are the two signals used in two signal model?
1)MHCs and TCRs
2)B7.1/7.2 and CD28
Without out these cells cant be killed
What is colonal expansion?
Production of many T-cells with T-cell receptors the MHC peptide complex. Production of a daughter cell from only one cell.
What does IL-2 cause?
Produced by T-helper cells cause proliferation into multiple more T-cells
What T-cell is cytotoxic?
CD8 T-cell
How does a T-cell become CD8 T-cell?
They interact with APCs and detect pathogenic peptides on MHCs they then become cytotoxic T-cells
What killing mechanisms do cytotoxic T-cells have?
They use:
- Perforin
- Granzymes
- Granulyson
What does perforin do?
Aids in delivering contents of granules into the cytoplasm
What are granzymes?
Serine proteases that when in the cytoplasm initiate apoptosis
What is Granulysin?
Antimicrobial
What is the development process of T-cells in the thymus? (For CD4 and CD8)
Double negative (1,2,3,4) and then double positive then to single positive. Leaves one receptor on the cells by its self.
Where do T-cells mature?
In the thymus
How do T-cells recognise infected cells?
Through MHC molecules on antigen presenting cells recognised by the TCR.
What are the functions of CD4 Helper cells?
Provide help to CD8 T-cells and B-cells
What are the function of CD8 cytotoxic T-cells?
When activated are cytotoxic, they kill virally infected and malignant cells
What other molecule does TCR associate with to transduce a signal?
They associate with CD3 molecules as they have an internal domain to transduce signal unlike the TCR.
What’s an MHC?
Major histocompatibility complex
Where do you find MHC class 1 molecules?
Found on most uncleared cells, present endogenous antigens. Self proteins,pathogenic proteins,then present to a cytotoxic T-cell
Where do you find MHC class 2?
Found primarily on APCs display exogenous antigens.
What does MHC molecules being highly polymorphic mean?
High genetic diversity within their population.
What are the 3 professional APCs?
Dendritic cell
Activated macrophage
Activated T-cell
Cells express MHC 1 are thought of as what?
Target cells -( virus infected malignant or aging)
How are T-cells activated?
Dendritic cells take up pathogens and traffic them to the lymphnode where they interact with naive T-cells activating them into CD8/CD4 T-cells
What is the costimulation 2 signal T-cell model?
Need MHC and TCR and B7.1/7.2
How do T-cells reproduce?
Clonal expansion
What are cytotoxic T-cell weapons?
Perforin
Granzymes
Granulysin
What is perforin?
Aids in delivering contents of granules into cytoplasm
What are granzymes?
Serine proteases initiate apoptosis once injected into cytoplasm
What is granulysin?
Antimicrobial
