Several mechanisms were identified at the molecular level: expression of the heparan sulfate-degrading enzyme heparanase is induced in infiltrating CD4+ T cells [147], and accumulation of versican and the 4-sulfated glycosaminoglycan side chains of chondroitin sulfate proteoglycans in the perivascular cuff boost the activity and migration of leucocytes across the blood–brain barrier, which worsens the clinical severity of multiple sclerosis [148]. The gene discussed is VCAN; the disease is multiple sclerosis.