From what I understand, only the oligodendrocytes are affected in multiple sclerosis, and they are attacked by T cells which cross the blood-brain barrier. This leads me to two questions:

  1. How is the blood-brain barrier affected in MS that allows T lymphocytes to cross the barrier?
  2. Why do the T lymphocytes attack the oligodendrocytes? And when they do, what is the mechanism for de-myelination?

Thank you in advance!