The Thymus and Development of T Lymphocytes: pg 34

Question 1

The T cell precursor migrates to the thymus from the ________________.

Answer 1

Bone marrow

Question 2

T/F - Foreign antigens never reach the thymic compartment.

Answer 2

True

Question 3

What cells are within the thymus?

Answer 3

Dendritic cells
Macrophages
Epithelial cells
Pre-T cell

Question 4

Explain positive selection.

Answer 4

If thymocytes do not bind to HLA class I or HLA class II molecules they will die. So the thymocytes that do have these HLA molecules will be positively selected. Thymocytes at this point are CD4+CD8+

Question 5

What is negative selection?

Answer 5

This process removes thymocytes that bind to self-antigen-HLA molecules too strongly. These cells are signaled to die in order to prevent autoreactivity or autoimmune disease. The cells then are either CD4+ or CD8+ but not both.