José Conejo-Garcia talks about his discovery of PILAR The immune system protects us from a host of pathogens, but in some cases it's actually the cause of health problems. T cells, a type of white blood cell that is a key player in the immune system, become activated when they encounter antigens. Usually, those antigens are signs that a pathogen is trying to get a foothold in the body, so the response of T cells is essential to fighting off disease. But when the antigen is actually a self-antigen--when it is part of the host and not an invader--a response by T cells can result in swelling, inflammation, and pain. José Conejo-Garcia, a professor of microbiology and immunology, has discovered a receptor, which he named "PILAR," that helps to determine whether T cells respond to an antigen. This is a web extra to an article that appeared in the Fall 2008 issue of Dartmouth Medicine Magazine. To read the article, go to: http://dartmed.dartmouth.edu/fall08/html/disc_pilar.php