The relevance of the VLA-4/VCAM-1 axis for B-cell trafficking into the CSF is further underlined by the reduced trafficking capacities across the choroid plexus displayed by B cells obtained from MS patients exposed to the VLA-4 blocking agent natalizumab as shown in this study and the overall efficiency of natalizumab in the treatment of MS (38, 39). This evidence concerns the gene VCAM1 and myeloid sarcoma.