The Tantalizing Tale of T Cells Flashcards
iNK T cells
separate population of alpha beta T cells that recognize glycolipids complexed in non-classical HLA molecules called CD1d, function through cytokines. develop prior to any VDJ rearrangments
gamma delta T cells
separate population of T cells with a unique receptor
order of recombination in alpha beta T cells
beta first: VDJ recombination, alpha locus second: VJ recombination
co-receptor molecules
either CD4 (class II MHC associations, function: suppress/help B cells) or CD8 (class I MHC associations - function: kill)
CD3 subunits
one gamme, one delta, two zeta: non-covalently associated with alpha-beta TCR dimer
the thymus
formed by epithelial cells, mesenchymal cells, and bone marrow derived hematopoietic cells that become thymocytes; has a few dendritic cells and macrophages but NO B CELLS; 3-d meshwork
3-d meshwork
of the thymus, lost in lymphopenic people, formed by the interaction of epithelial cells and the thymocytest
the TCR’s developmental fate
is determined by its weak interaction with a dendritic cell or epithelial cell’s peptide/MHC receptor (from alpha/beta T cell to the following, based on interaction – MHC II:CD4::MHC I:CD8::CD1d/glycolipid:NK)
double positive; single positive; double negative
both CD8 and CD4 receptors; either or; neither nor
Double Positive T cells
have both CD8 and CD4 molecules and are immature and are found in the thymus
Double Negative T cells
have neither receptor and are therefore B cells, found in lymph nodes
co-receptor development pattern
double negative to double positive to single positive
thymopoiesis
when double negative cells become double positive. require the cytokine IL-7 to do so.
beta chain rearrangements occur
in the double negative stage, unless a successful TCR beta locus (and pre-TCR) is expressed, the cell is arrested in the DN3 stage
alpha chain rearrangements
are initiated once the cell successfully leaves the DN3 stage, and re-expresses RAG1/2. during alpha locus rearrangements (VJ), the cell is double positive
3 life/death developmental fates of a alpha/beta expressing T cells
- death by neglect (what happens behin the scenes during positive selection) – when the T cell finds no HLA/peptide to interact with in the thymus 2. survival (positive selection) – when the T cell has a weak affinity to a self-HLA/self-peptide 3. death by negative selection – when the T has a strong affinity to a self-HLA/self-peptide
AIRE
a transcription factor that forces tissue specific antigens to be expressed in the thymus - mutations in AIRE cause autoimmunity
TRECs
T Cell Receptor Excision Circles: chromosomal DNA with deleted unused V and or D/J regions found in newly ‘generated’ T cells leaving the thymus, measured clinically to determine immunodeficiencies in newborns
FY720
immunosuppressive drug that blocks the movement of T cells into the blood via attachment to the S1P receptor (which usually binds to the high levels of S1P found in the blood
CD4 count
important for indicating an HIV infection - CD4 numbers less than 400 “are of immediate concern for opportunistic infections”
Spleen T vs. B cell count
T cells ~ 20 % (minority)
activation of what three parts of a T cell is necessary to generate a make it an “effector T cell”
- the TCR 2. a costimulatory molecule (CD28/ICOS) 3. cytokine receptor
effector T cells
no longer need three signals now that they are “committed memory T cells”
T cell and APC “velcro” is comprised of what
LFA-1, ICAM-1, VLA-4, CD2 (interactions occur in T cell enriched zones in the lymph node, the best APC is a dendritic cell)
