Multiple myeloma begins when one B cell of approximately 10 billion in the body undergoes mutations that enable it to outgrow most other cells in the bone marrow. When the neoplastic clone consists of 1011 B cells, serum electrophoresis barely detects the clone's signature molecule, a monoclonal immunoglobulin; with 1012 members, the gammopathy is unmistakable; and with 1013 myeloma cells, symptoms begin to appear. Not the least of the clinical problems in patients with myeloma is susceptibility to bacterial infection, a paradox given the huge amounts of gamma globulin secreted by the tumor. But most of the antibodies in the . . .