Immunology - 24 Flashcards
Where to developing T cells acquire their TCR?
In the thymus. Regulated by cytokine secretion by thymic cells
Is the TCR secreted?
No, it is always on the T cell surface
What are the two flavors of TCR?
- alpha-beta: one chain of each, much more abundant
* lamba-kappa: one chain of each, most commonly associated with skin and mucosal tissue
What genes encode the variable region of the TCR?
V, D, and J genes (like BCR)
Does the TCR experience isotype switching and affinity maturation like the BCR?
No. All progeny will have the same antigen specificity
Once the TCR has been rearranged genetically and is expressed on the surface of the cell, the cells undergo a selection process. At this point the cell is called?
A double positive (CD4+CD8+) thymocyte
What are the two rounds of thymic selection?
- Positive selection for self MHC
* negative selection against self antigen*
Where is there a checkpoint in positive selection?
If the thymocyte does not interact with a MHC molecule (I or II), then the cell will undergo apoptosis
Why would you want self recognition for T cells and not for B cells that we talked about?
The T cell receptor recognizes peptides through engaging the MHC molecule so it has to know the MHC molecule itself
What are the two goals of positive selection?
- Self recognition
* lineage choice
What is lineage choice?
If it comes into contact with MHC class II, CD8 is lost if it comes into contact with MHC class I, CD4 is lost
What are the overall goals of positive selection?
- To make sure mature T cells can recognize our own MHC molecules as self and not foreign
- consequence: double positive thymus sites become single positive CD4+ or CD8+ T cells
What are the overall goals of negative selection?
To make sure mature T cells bind to self MHC molecules presenting foreign peptide or antigen
Which cells will undergo apoptosis in positive and negative selection?
Positive - those that do not interact with MHC I or II
Negative - those that bind self antigen
