title: Delayed acquisition of somatic hypermutations in repopulated IGD+CD27+ memory B cell receptors after rituximab treatment.
abstract: OBJECTIVE
  Transient B cell depletion by rituximab has been used with clinical efficacy in the treatment of patients with rheumatoid arthritis (RA). Previous studies of B cell repopulation have shown long-term numerical reduction in memory B cells. Non-class-switched IgD+CD27+ memory B cells, in particular, repopulate slowly. This study was undertaken to determine whether mutational acquisition in individual B cell receptors in repopulating class-switched and non-class-switched memory B cells is affected by rituximab.
  
  
  METHODS
  Cells obtained from 16 RA patients, 4 healthy donors, and 3 patients who underwent allogeneic stem cell transplantation (ASCT) were analyzed using single B cell sorting followed by nested polymerase chain reaction and Ig V(H)3 sequencing.
  
  
  RESULTS
  There was a delayed acquisition of mutations in Ig receptors of IgD+ memory B cells over a period of 6 years after a single course of rituximab. One year after rituximab treatment, 84% of single repopulating IgD+CD27+ B cells were unmutated, and no highly mutated Ig receptors were found (compared with 52% before therapy). Over time, increasing numbers of mutations were detected. Even 6 years after rituximab treatment, however, mutations in IgD+ memory B cells were still significantly reduced. In contrast, class-switched memory B cells repopulated with quantitatively normal mutations. In comparison, in patients undergoing ASCT, IgD+ memory cells repopulated earlier with higher mutations in Ig receptors.
  
  
  CONCLUSIONS
  Our data suggest that IgD+ memory B cells are particularly susceptible to the effects of rituximab, with delayed acquisition of mutations in their Ig receptors still evident 6 years after a single course of rituximab. Our findings indicate that these cells have different requirements for mutational acquisition compared with class-switched memory B cells.
authors: Medizinische Klinik II, Department of Rheumatology and Clinical Immunology, University of Würzburg, Würzburg, Germany.
authors: Khalid
authors: K
authors: Muhammad
authors: Petra
authors: P
authors: Roll
authors: Hermann
authors: H
authors: Einsele
authors: Thomas
authors: T
authors: Dörner
authors: Hans-Peter
authors: HP
authors: Tony
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000009:adverse effects*; D058846:Antibodies, Monoclonal, Murine-Derived; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D015322:Gene Rearrangement, B-Lymphocyte / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007156:Immunologic Memory / Q000187:drug effects* / Q000276:immunology; D008875:Middle Aged; D011961:Receptors, Fc / Q000187:drug effects* / Q000276:immunology; D000069283:Rituximab; D027041:Somatic Hypermutation, Immunoglobulin / Q000187:drug effects*; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018501:Antirheumatic Agents; D011961:Receptors, Fc; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7; C050855:immunoglobulin D receptor; D000069283:Rituximab