T cells Flashcards
How does a vaccine or previously having a virus increase the speed of virus being destroyed?
If you’ve been vaccinated against or had the virus when the virus antigens enter your body the B cell antibodies will recognise the antigens and destroy them removing virus faster than if you’re unvaccinated or haven’t had virus before
How do different virus strains affect vaccine effectiveness?
Viruses can create new strains which will have different antigens to ones before hence we need to get ‘booster vaccines’ or yearly vaccinations to reduce the chance of being affected by the strain
What are cytotoxic T cells required for?
Production of antibody from B cells
Process of MHC-I (endogenous) antigens
Proteins produced in cytoplasm, enzyme degrades proteins in cytoplasm into peptides, loading onto MHC-I in ER, sent to cell surface for immune surveillance from T cells
Process of MHC-II (exogenous) antigens
Phagocytosis of exogenous antigens into phagolysosome vacuole which degrades proteins into pepetides
Phagolysosome contains empty MHC-II which are loaded up and presented to T cells
What are T cells?
Lymphocytes that arise in the bone marrow and fully develop in thymus
They recognise MHC/peptide complexes through TCR
What do T cells express?
Express T cell receptor (TCR) with co-receptors (CD4 or CD8)
DNA is rearranged in thymus so each TCR are unique
What does the thymus help T cells with?
Helps T cells to develop
Screens T cells to get rid of auto-reactive T cells
What are immature T cells?
TCR genes in germline state that are untouched , found in bond marrow
What are mature T cells?
Naive T cell expressing unique antigen receptors that differ from each other
How are thymic genes rearranged?
Immature T cells (thymocytes) rearrange the variable parts of their TCR genes in the thymus - essentially random process
Ensures that individual T cells are unique in terms of their TCR, creates diversity in T cell repertoire
What is the variable region of TCR?
The tip of TCR is variable
It enables each T cell to dock into a different region of T cell
How are CD4 and CD8 expressed on T cells?
CD4 and CD8 molecules assist with the docking of TCR onto MHC-II or MHC-I respectively
CD4 prefer to interact with MHC-II
CD8 prefer to interact with MHC-I
Activated T cells vs Non activated T cells
T cells that have not been activated by MHC/peptide are naive
Activated T cells are known as ‘effector T cells’
What are effector T cells?
Cells that can kill virus infected cells or secrete cytokine
Can form a subset of memory T cells which are able to hang around for long periods of time
What are the functions of a CD8 T cell?
Recognise MHC-I / peptide
Develops into cytotoxic T lymphocyte (CTL) / cytotoxic T cell
What are Cytotoxic T Lymphocytes?
They release granules that are very specific and when recieved signals will be secreted and kill virus meaning the virus can no longer hijack host cell and the cell is destroyed
