Whether BBB dysfunction is the cause or the consequence of MS is disputed, because activated T-Cells can cross a healthy BBB when they express adhesion proteins. Apart from that, activated T-Cells can cross a healthy BBB when they express adhesion proteins. (Adhesion molecules could also play a role in inflammation) In particular, one of these adhesion proteins involved is ALCAM (Activated Leukocyte Cell Adhesion Molecule, also called CD166), and is under study as therapeutic target. Another protein involved is CXCL12, which is found also in brain biopsies of inflammatory elements, and which could be related to the behavior of CXCL13 under methylprednisolone therapy. Some molecular biochemical models for relapses have been proposed.