Clonal analysis of B cell receptor repertoires suggest CS memory B cells represent the bulk of immunopathic B cells trafficking from the blood into the CNS during MS.15,29 We delineated memory B cells according to the presence of CD27, and surface IgD, into class switched (IgD−) and unswitched (IgD+) subsets. The gene discussed is PPIB; the disease is myeloid sarcoma.