Question

The full activation of naïve T cells takes 4 to 5 days and is accompanied by marked changes in the homing behavior of these cells. These occur because of changes in the expression of several cell-surface adhesion molecules that direct the migration of T cells. Thus, many armed effector T cells lose expression of the L-selectin molecule that mediates homing to the lymph nodes, whereas the expression of other adhesion molecules is increased. One important change is the marked increase in the expression of the α4 integrin VLA-4, which binds to what?

a) VCAM-1
b) L-selectin
c) Mac-1
d) LFA-1
e) ICAM-1

Answer 1

The α4 integrin VLA-4, which increases in expression on activated T cells, binds to VCAM-1, enabling T cells to migrate to the appropriate sites of inflammation. The correct option is A.

Step-by-step explanation:

The marked increase in the expression of the α4 integrin VLA-4 on T cells binds to VCAM-1, which helps direct the T cells to sites of inflammation. This is significant as it underlines the importance of adhesion molecules in the immune system's response to infection.

The T cells' homing behavior alteration allows them to exit the lymph nodes and travel to sites of infection, which is a crucial part of the adaptive immune response.