2.6 - Development of T cells Flashcards
Function of primary lymphoid organs
Maturation of immature cells (lymphoid stem cells) into immunocompetent lymphocytes
Role of thymus
Maturation of thymocytes into T lymphocytes (T cells)
Precursor T cells are derived from the ___ stem cell in the bone marrow and travel to the ___
Hematopoietic
Thymus
Once T cells are mature, where do they go?
To secondary lymphoid organs like the spleen, lymph node, and gastro associated lymphoid tissue (GALT)
What are the 2 portions of the thymus?
Cortical and medullary
What cell types is the cortex made of?
Cortical epithelial cell
Thymocyte
cortical epithelial cell origin
Thymic origin
Thymocyte origin
Bone marrow
Cell types of the medulla
Medullary epithelial cell
Macrophage
Dendritic cell
Macrophage origin
Bone marrow
Dendritic cell origin
Bone marrow
When progenitor lymphoid cells come into contact w/ thymus, they enter around the ___ region and go up into the ___
Medullary cortical
Cortex
As T cells develop, they go from ___ to ___ region
Cortex to medullary
At birth the thymus is ___
Fully developed
Thymus is replaced by fatty material as you get older. This is called
Involution
Does loss of thymus mean loss of cell mediated immunity (CMI)?
No
Long living T cells and some self-renewal
When the uncommitted progenitor cell from the bone marrow comes into contact with the thymic epithelium it gives rise to ___
double negative cells (CD4 and CD8)
Marker for uncommitted progenitor cell?
CD34
CD34 marker is important for bone marrow
Transplantation
When cell becomes committed to being a T cell, it loses ___ expression and expresses T cells associated with ___ marker
CD34
CD2
CD34 is a ___ surface marker
stem-cell
CD2 is involved in
adhesion and signaling
Are CD4 and CD8 active or inactive in double negative thymocyte committed to T cell lineage
Inactive
TCR genes begin to ___ when the double-neg thymocyte committed to the T cell lineage
Rearrange
Thymocyte expresses a receptor called ___
Notch 1
Where is Notch 1 located
Thymic epithelium cells
Describe notch 1
Driving force in thymic epithelium where thymocytes can be driven to become mature T lymphocytes
When notch ligand’s attached it drives T cell towards ___
development
What committed steps leave the thymus?
Committed gamma:delta T cell from beta, gamma, delta rearrangement
Committed gamma:delta T cell from alpha, gamma, delta rearrangement
What is the result of beta, gamma, delta rearrangement
Committed gamma:delta T cell and committed double positive thymocyte are produced
What does an uncommitted double positive thymocyte consist of?
CD8, CD4, and beta chain
What is the result from alpha, gamma, delta rearrangement?
Committed gamma:delta T cell and committed alpha:beta T cell
Majority of T cells are ___
committed alpha:beta T cell
During rearrangement T cells are committed w/ gamma:delta T cell receptor or an uncommitted double positive thymocyte. Both will be ___
CD3+
Both gamma:delta and alpha:beta T cells express
CD3
An antibody to CD3 is used in supressing and removing T cells in patients undergoing a
Graft rejection
In the blood over ___ of the circulating T cells express the alpha:beta receptor
90%
T cells expressing the gamma:delta receptor are mainly located in the
epithelium surfaces including mucosal surfaces
Where are the 2 check points for TCR?
After rearrangement of beta genes
After rearrangement of alpha genes
If you can’t rearrange beta or gamma: delta at the checkpoint for pre-TCR, and you can’t rearrange alpha or gamma:delta at the checkpoint for TCR, what happens?
Cell dies
RAG-1 and RAG-2 function
lymphoid specific recombinase
TdT function
N-nucleotide addition
CD3 and CD2 function
signal transducation
Where can you find dead cells?
Cortex and cortex medullary region
Describe positive selection
Stimulation of T cells that recognize correct MHC marker and elimination of those that don’t
What happens if TCR interacts with MHC 1?
CD4 dies and end up with CD8 T cell
What happens if TCR recognizes MHC II?
CD8 dies and end up with CD4 T cell
Describe negative selection
Removal of T cells that bind and recognize self antigens that are associated with MHC
Negative selection depends on ___ that express self antigens that come from thymus in blood
APC (dendritic cells and macrophages)
Define peripheral tolerance
- Occurs after mature naive T cells leave the thymus
- occurs in peripheral blood or organs associated with
What are the antigen presenting cells for positive selection?
Cortical epithelial cells
- Thymically derived
What are the antigen presenting cells for negative selection?
Dendritic cells and macrophages
- Derived from bone marrow
T cells that leave the thymus are known as ___
Mature naive T cells
