2.1.6 development of T-lymphocytes Flashcards
______ stem cells can differentiate into all possible cell types
Totipotent
______ stem cells have the ability to differentiate into almost all cell types, but lack the capacity to contribute extraembryonic tissue
Pluripotent
____ stem cells have the potential to give rise to cells from multiple, but a limited number of lineages. an example of this is a mesenchymal stem cell or a _____
Multipotent, Hematopoietic stem cell
The ____ is a primary lymphoid organ that plays a role in maturation of thymocytes into ______
thymus
T-lymphocytes
The _____ is where B-cells mature
bone marrow
Precursor T-cells are derived from the ______ stem cell in the _____ and travel to the _____
Hematopoetic stem cell
Bone marrow
thymus
if a cell stays in the bone marrow to mature it becomes a _______
B-cell
In the ______ area of the thymus, thymocytes are tightly packed and have a large cell turnover
Cortical
As thymocytes mature in the thymus, they migrate to the ____ portion
medullary
Progenitor lymphocyte cells enter the thymus around the ______ and then go up into the ______
Medullary cortical region
cortex
what are the two types of cells in the cortex we need to know? Where do they originate?
- cortical epithelial cell
- thymus - thymocyte
- bone marrow
what are the two types of cells in the medulla we need to know? Where do they originate?
- Dendritic cell
- bone marrow - macrophage
- bone marrow
_______ can be found in both the cortex and medullary region
thymocytes
When is the thymus fully developed?
birth, after this it experiences Involution and degenerates
the thymus is replaced by what kind of material during involution?
Fatty material
which of these thymus would you expect to belong to an infant? which would belong to an elderly person?
A- infant, not very involuted
B- elderly, very degenerated
when the uncommitted progenitor cell from the bone marrow comes in contact with the thymic epithelium it gives rise to ________. what does this mean?
Double negatives
- it is CD4/CD8 negative
______ is the marker of immaturity/ an uncommitted progenitor
CD34
when does a cell lose the CD34 expression?
when it becomes committed to become a T-cell
what do double negative T-cells express?
CD2
Thymocyte expresses a receptor called ______ which is activated when it interacts with the ____ ligand on the thymic epithelium
Notch1
Notch ligand
what does the Notch 1 receptor do once activated?
drives T cell towards T cell development
How does an uncommitted progenitor give rise to alpha/beta and gamma/delta cells?
- Uncommitted progenitor → committed double negative T-cell progenitor
- T-cell progenitor now goes through Beta or Gamma/Delta rearrangements
- Gamma/delta cells leave thymus
- Uncommitted double-positive thymocyte with Beta (has CD8 and CD4) goes through another set of rearrangements: either alpha OR gamma delta
- gamma/delta cell will leave and go to thymus
- now theres also a committed alpha/beta cell (majority)
which rearrangement do most cells go through? Beta or delta/gamma?
Beta, its easier to just rearrange one
the majority of T-cells are _____
alpha/beta
Both alpha/beta and delta/gamma express ______
CD3
When can an antibody to CD3 be used?
in suppressing and removing T cells in a patient who is undergoing a graft rejection
Where are gamma/delta t-cells found?
epithelium surfaces including mucosal surfaces
where are the two TCR checkpoints?
- during the first rearrangement (if neither gamma/delta or Beta rearrange, the cell will die
- second rearrangement (if cant rearrange gamma/delta or alpha, cell will die)
what do CD3 and CD2 function in?
signal transduction
why is there significant cell death in the cortical area?
positive and negative selection
______ selection is when the T-cell receptor is removed if it doesn’t recognize the appropriate MHC
Positive
_______ selection is when self-recognizing t-cells are removed
negative
how do T-cells become either CD4 or CD8 positive?
if the TCR interacts with MHC1, CD4 is lost (will be CD8)
if TCR interacts with MHC2, CD8 is lost (will be CD4)
_____ tolerance is negative selection in the thymus, while _____ tolerance is negative selection in self-reacting cells that leave the thymus
Central
Peripheral
what are the APCs for positive selection?
cortical epithelial cells (thymically derived)
what are the APCs for negative selection?
dendrites, macrophages (bone marrow derived)
