Comment by sam537

There are two types PD1 and PDL1 inhibitors.

Cancer cells (and our own cells) express PDL1. Our immune cells touch PDL1 with their PD1 and if this connection works then the immune cell does not kill.

If the connection does not work (PDL1 or PD1 absent) the immune cell will kill the target cell.

These antibodies either block PDL1 or PD1.