Common english name for tissues which are separated from the blood by blood-tissue barriers?

Question

Which general term is used to denote such organs/tissues as: brain, testis, thymus etc., which are separated from the blood by blood-tissue barriers?

Answer 1

These are also known as 'privileged sites'.

Special immune cells manage these areas, but still, many viruses such as HIV and more can 'hide out' in these locations, sometimes for decades.