Immunologic privilege in the eye and the fetus

Some regions of the body are notably tolerant to transplants of foreign tissues. This 'immunologic privilege' has previously been assigned to the isolation of these sites from the lymphatic system, thus preventing interaction with cells of the immune system. But recent work has largely overturned this theory; antigens can not only reach lymphatic and blood vasculature tissues but can also generate immune responses. Concentrating on the anterior chamber of the eye and the pregnant uterus, Wayne Streilein and Thomas Wegmann suggest that immunologic privilege arises instead from the specific active suppression of a rejection response.