T cells Flashcards
DC presentation of viral antigens via MCH-2
DC phagocytose virus particles or virus infected cells
viral antigen is then treated as an exogenous antigen and is fed into the MHC-2 pathway
this allows activation of helper T cells during a viral infection dying infected cells get swallowed up by the dendritic cells and these have virus particles within them.
DC cells can load up both pathways
dendritic cells in the skin
Langerhans cells
they have a large number of MHC-2, large surface area that can sample anything that comes into the skin.
Lymph node
T cells are colourless and B cells are coloured.
DC are blue/ green and are nestled amongst the areas of clear T cells
individual DC makes contact with many T cells, there is a constant movement of T cells in and out of lymph node.
most wont make contact with DC and will circulate and leave.
if they do make contact and get the right signals they will stop around the DC and cell divison will begin of the T cells.
T cells
are lymphocytes that arise in the bone marrow and fully develop in the thymus
t cells express T cell receptor (TCR) with co-receptor (either CD4 or CD8).
these recognise MHC/ peptide complexes
once developed they travel from the thymus to the lymphoid organs, blood and tissues.
in the thymus they undergo TCR gene rearrangement and come out mature T cells with unique receptors that can recognise many different peptides
CD4
will only interact with MHC-2 / peptide on the antigen presenting cell
CD8
will only interact with MHC-1 / peptide on the antigen presenting cell
T cell differentiation
T cells that have not been activated by MHC/ peptide are “naive”, they haven’t experienced an antigen and haven’t been triggered yet
activated T cells are also known as effector T cells.
CD4 T helper cell
recognise MHC-2 / peptide
helps CD8 become cytotoxic (essential)
Helps B cell make antibody
this is by the release of the soluble immune hormone called cytokines that are released from the CD4 and DC cells. they can also act on themselves or other cells
CD8 T cell
recognise MHC-1/ peptide
develop into cytotoxic T lymphocyte (CLT) aka cytotoxic T cell
cytokines produced by CD4 T cells help activate CD8 cells.
Cytotoxic T lymphocyte
bind to the MHC-1/ peptide complex on virally infected cells and this initiated cell death (apoptosis)
Memory T cells
in addition of formation of ‘effector cells” the T cell activation results in the formation of memory T cells.
Memory CD4 or CD8 T cells reside in the body for long periods of time
memory T cells become effector cells much quicker than naive T cells
this is what vaccination does it speeds up the activation process and it will be much faster.
Natural Killer cells
lymphocyte linage, distinct from T cells
natural killer cells do not have T cell receptor
kill tumor cells or virus infected cells that have low or absent MHC-1
