In a healthy brain, the blood-brain barrier protects the vital organ from things that could damage it – this includes the immune system’s B lymphocytes. With MS, the barrier is compromised and this allows large amounts of lymphocytes to get to the brain and attack the myelin sheath. One of the diagnostic tests for MS is to look for the presence of B lymphocytes in the cerebrospinal fluid, as this is a classic marker.
Scientists, working with mice and human cells in vitro, showed that blocking a molecule called ALCAM (Activated Leukocyte Cell Adhesion Molecule), they could lessen the amount of B-cells entering the brain and therefore slow the progression of MS. ALCAM is expressed at higher levels in people with MS, and is what allows B-cells to cross the blood-brain barrier.
B-cell-directed therapies already exist, but in their current form they deplete all B-cells, which leaves people more vulnerable to cancers and infections. The researchers hope this discovery will pave the way for new drug therapies to treat MS.