Lec 42: Development of T Cells Flashcards Preview

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Flashcards in Lec 42: Development of T Cells Deck (14):

What are the 4 phases of T lymphocyte development in the thymus?

1. Arrival in the thymus and antigen receptor expression
2. Positive selection
3. Negative selection
4. Terminal antigen-stimulated differentiation into effector and memory cells


What are the 2 types of diversity that contribute to 1x10^18 combinations of TCRs?

1. Combinatorial diversity - somatic recombination of TCR alpha and beta loci

2. Junctional diversity - generated at joints between gene segments


What is the purpose of T lymphocyte positive selection?

To ensure T-cells will recognize self-MHC (and kill those that do not)


What is the purpose of T lymphocyte negative selection?

To delete T-cells that would react to self-antigen


What is the purpose of thymic epithelial cells in T lymphocyte positive selection?

Thymic epithelial cells present MHC I and II, along with available proteins acting as antigens, to the "T-cell in training" to see how it will react


When is a T-cell considered activated (effector T-cell)?

After it encounters antigen


What are the 3 possibly destinies for a T lymphocyte (there are more than 3, but what was described in class)?

1. CD4+ Th1 (helper T-cell)
2. CD4+ Th2 (helper T-cell)
3. CD8+ Tc (cytotoxic T-cell)


In terms of location, what is different about the development of T-cells as compared to B-cells?

Both originate in the bone marrow, but T-cells are "educated" and matured in the thymus


Which live longer - B-cells or T-cells?



In terms of thymus structure, what general direction do developing T lymphocytes move as they are developing?

From the outer cortex to the inner medulla


Review: what cells are considered lymphocytes?

B-cells, T-cells, and Natural Killer (NK) cells


At the start of positive selection in the thymus, do T lymphocytes have CD4, CD8, neither, or both expressed on their surface?

Both CD4 and CD8 - "double positive" (TCR is also expressed at this point)


During T lymphocyte positive selection in the thymus, is it desired for the TCR to bind weakly/none or moderately/strongly to the presented MHCs?

Moderately or strongly


During T lymphocyte negative selection in the thymus, is it desired for the TCR to bind moderately or tightly to the presented MHC:self-peptide complex?

Moderately; if it binds too tightly to the self-peptide:MHC complex, the T lymphocyte is eliminated

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