Answer :
PD-L1 (Programmed Death-Ligand 1) is a protein that plays a significant role in the immune system by interacting with its receptor PD-1 (Programmed Death-1), which is found on the surface of T cells. This interaction is a part of the body's immune checkpoint mechanism, which helps to regulate the immune system and prevent it from attacking the body's own cells, but it can also be exploited by cancer cells to avoid being targeted by the immune system.
Let's go through the given options:
(A) The drug Nivolumab works by binding to PD-L1.
- This statement is incorrect. Nivolumab is a monoclonal antibody that targets PD-1, not PD-L1, to block the connection between PD-1 and PD-L1, thereby enhancing the body's immune response against tumors.
(B) PD-L1 can only bind to PD-1.
- This statement is also incorrect. While PD-L1 primarily interacts with PD-1, it can also bind to another receptor known as B7-1 (CD80) in specific situations.
(C) Binding of PD-L1 to PD-1 reverses T cell exhaustion.
- This is incorrect. Binding PD-L1 to PD-1 actually contributes to T cell exhaustion, reducing their proliferation and ability to attack tumor cells.
(D) Blocking PD-L1 can strengthen anti-tumor activity.
- This statement is true. By blocking PD-L1, the inhibition on T cells is lifted, which enhances the immune system's ability to target and destroy cancer cells, making this a viable therapeutic strategy in cancer treatment.
(E) It is found naturally on immune cells, and must be inhibited by tumors to prevent apoptosis.
- This statement is incorrect in its implication. PD-L1 is indeed found on normal cells and some immune cells as part of normal immune regulation, but tumors express PD-L1 to evade immune detection, not to avoid apoptosis directly.
Therefore, the correct and true statement regarding PD-L1 from the given options is (D) Blocking PD-L1 can strengthen anti-tumor activity.
