It's just talking about a narrow class of immune system white blood cells. If you want to understand the lingo better, read the link to understanding MS 101 at the bottom of my post and if you survive that, there's a 102 at the end of 101. Ken
It would be really nice to be able to put links in here
If I have included a bad link, google the word "Scholar", click link for "Google Scholar". Search for the name of the paper and author in Google Scholar.