In my experience it worked quite well in mice. Now that I want to see it in humans, it seems that all literature uses an antibody developed by a professor from Freiburg (Germany), and the commercial available one do not seem to work.
Hello! I have a teammate that has the same problem. She always says that the only anti-human KLRG1 is the prepared by this teacher. You can ask him for it. Apparently, there is not option. Sorry for bad news. Lucky!