Question

Circulating naïve T cells will _________

a. Enter the thymus though HEV thanks to the CCL19 and CCL21 gradient.
b. Enter the secondary lymphoid tissue though HEV thanks to the CCL19 and CCL21 gradient.
c. Will not be able to pass through the HEV if CCR10 is not present on the T cell surface.
d. B&C

Answer 1

Circulating naive T cells enter secondary lymphoid tissues through high endothelial venules, guided by the CCL19 and CCL21 gradient, where they interact with APCs and can become activated helper T cells.

Step-by-step explanation:

Circulating naïve T cells will enter the secondary lymphoid tissue though high endothelial venules (HEV) thanks to the CCL19 and CCL21 gradient. The process of naive T cells circulating through the bloodstream and lymphatic system, ultimately entering the secondary lymphoid organs like lymph nodes, spleen, and tonsils, is essential for their activation through the presentation of specific antigens by antigen-presenting cells (APCs).

Once they encounter their specific antigen in the context of an APC presenting via MHC II molecules, CD4+ naive T cells become activated and differentiate into helper T cells which then assist in activating other immune cells, like B cells and CD8+ T cells, which become cytotoxic T cells responsible for killing infected cells.