Multiple sclerosis (MS) is associated with production of oligoclonal IgG antibodies within the central nervous system (CNS), but less is known about the status of IgA-producing cells. Pröbstel et al. detected clonally expanded IgA+ cells in cerebrospinal fluid and tissue adjacent to areas of active MS-associated demyelination. Recombinant IgA antibodies assembled from the cloned antibody genes…