Effect of clinical status and treatment on the frequency of CD5+ B cells in patients with myasthenia gravis.

CD5+ B cells comprise a subset of B lymphocytes that may play a pathogenetic role in the development of human autoimmune disease. We previously reported a high-frequency phenotype (greater than 30% CD5+ B cells) in the peripheral blood of 57% of myasthenia gravis (MG) patients and 13% of controls. We have now examined additional patients (n = 41) and controls (n = 27) and continue to find that 44% of MG patients have a high-frequency phenotype of CD5+ B cells compared with 7% of controls. Serial studies showed that the frequency of CD5+ B cells in peripheral blood remained fairly stable for controls and that it may decrease with immunosuppressive therapy of MG patients. In patients receiving anticholinesterase only or no therapy (n = 21), the age at onset of MG, presence or absence of detectable serum anti-acetylcholine receptor antibody, clinical extent of MG, and the duration of disease may affect the frequency of CD5+ B cells in the blood.