Test 3: T cell maturation Flashcards
What makes up the T cell Receptor?
one alpha and one beta chain; each has one constant domain–anchored into the membrane and a variable domain for epitope specificity
What components are part of the TCR Complex?
- TCR
- 2 CD3 molecules
- zeta chains for signaling
Where do T lymphocytes enter the thymus and what are they called at this point?
-found in subcapsular sinus and outer cortical regions; called THYMOCYTES
Where does most of the T cell maturation occur?
Cortex
What type of MHC molecules are expressed on thymic epithelial cells and dendritic cells?
Class I and II
What are the functions of thymic stromal cells?
- signal proliferation of immature T cells (IL-7)
- Direct transit of T cells from cortex to medulla (CCL21 andCCL19 are recognized by CCR7 on Tcell)
What are the causes of high apoptotic rates of cortical thymocytes?
- can’t produce a functional beta chain
- not positively selected by MHC molecules
- self-antigen negative selection
What occurs in Pro-T cells?
- Rag expression
- rearrangement of Diversity to Joining segments for beta chain
When do you know the Pro-T has transitioned to the Pre-T cell?
Variable segment rearranged and added to D-J
What parts of the TCR complex are present in the Pre-T cell stage?
-Beta chain, invariant alpha chain, CD3 and zeta proteins largest proliferative expansion during development
What is expressed in the double positive T cell?
- CD4 and CD8
- rearrangement of alpha chain (RAG)
- leads to migration to the MEDULLA
What segment is not included in alpha chains?
No diversity segment
What are the results of not having ‘allelic exclusion’ in the alpha chain?
- higher probability of successful alpha-beta TCR
- may express two different alpha chains–two different TCRs on a T cell
Where does selection of developing T cells occur?
-Cortex=location of thymic epithelial cells that display the self antigens on MHCs
When is CD4 vs CD8 made?
- MHC 1=CD8
- MHC 2=CD4
