<qa>  What is the abnormal immunoglobulin protein in MGUS produced by white cells called BThe abnormal immunoglobulin protein in MGUS is produced by white cells called B lymphocytes. Rituximab is approved to treat B cell lymphomas. Also, the drug showed promise in a recent study of patients with demyelinating neuropathy associated with production of antibodies from B lymphocytes directed against certain nerve proteins. Although the number of patients treated with Rituximab was small, the drug was well tolerated and caused significant improvement in several of the patients. 