In chronic autoimmune polyneuropathies including chronic inflammatory demyelinating polyneuropathy (CIDP), Multifocal Motor Neuropathy (MMN), and IgM anti-myelin-associated glycoprotein antibody demyelinating neuropathy (anti-MAG neuropathy), B cell involvement is supported by several pieces of evidence. This evidence concerns the gene MAG and chronic inflammatory demyelinating polyradiculoneuropathy.