title: Rituximab therapy reduces activated B cells in both the peripheral blood and bone marrow of patients with rheumatoid arthritis: depletion of memory B cells correlates with clinical response.
abstract: BACKGROUND
  Bone marrow (BM) is an immunologically privileged site where activated autoantibody-producing B cells may survive for prolonged periods. We investigated the effect of rituximab (anti-CD20 mAb) in peripheral blood (PB) and BM B-cell and T-cell populations in active rheumatoid arthritis (RA) patients.
  
  
  METHODS
  Active RA patients received rituximab (1,000 mg) on days 1 and 15. PB (n = 11) and BM (n = 8) aspirates were collected at baseline and at 3 months. We assessed B-cell and T-cell populations using triple-color flow cytometry.
  
  
  RESULTS
  Rituximab therapy decreased PB (from a mean 2% to 0.9%, P = 0.022) but not BM (from 4.6% to 3.8%, P = 0.273) CD19+ B cells, associated with a significant reduction in the activated CD19+HLA-DR+ subset both in PB (from 55% to 19%, P = 0.007) and in BM (from 68% to 19%, P = 0.007). Response to rituximab was preceded by a significant decrease in PB and BM CD19+CD27+ memory B cells (P = 0.022). These effects were specific to rituximab since anti-TNF therapy did not reduce total or activated B cells. Rituximab therapy did not alter the number of activated CD4+HLA-DR+ and CD4+CD25+ T cells.
  
  
  CONCLUSIONS
  Rituximab therapy preferentially depletes activated CD19+HLA-DR+ B cells in the PB and BM of active RA patients. Clinical response to rituximab is associated with depletion of CD19+CD27+ memory B cells in PB and BM of RA patients.
authors.affiliation: Department of Rheumatology, Clinical Immunology and Allergy, University of Crete, Medical School, Voutes, Heraklion, Greece. mnakou@hotmail.com
authors.forename: Magda
authors.initials: M
authors.lastname: Nakou
authors.forename: Georgios
authors.initials: G
authors.lastname: Katsikas
authors.forename: Prodromos
authors.initials: P
authors.lastname: Sidiropoulos
authors.forename: George
authors.initials: G
authors.lastname: Bertsias
authors.forename: Eva
authors.initials: E
authors.lastname: Papadimitraki
authors.forename: Amalia
authors.initials: A
authors.lastname: Raptopoulou
authors.forename: Helen
authors.initials: H
authors.lastname: Koutala
authors.forename: Helen A
authors.initials: HA
authors.lastname: Papadaki
authors.forename: Herakles
authors.initials: H
authors.lastname: Kritikos
authors.forename: Dimitrios T
authors.initials: DT
authors.lastname: Boumpas
mesh_terms: D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D018941:Antigens, CD19 / Q000276:immunology / Q000378:metabolism; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000188:drug therapy* / Q000276:immunology; D016175:B-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D001854:Bone Marrow Cells / Q000187:drug effects*; D005260:Female; D005434:Flow Cytometry; D006684:HLA-DR Antigens / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007156:Immunologic Memory / Q000187:drug effects*; D008213:Lymphocyte Activation / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D000069283:Rituximab; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018941:Antigens, CD19; D018501:Antirheumatic Agents; D006684:HLA-DR Antigens; D000069283:Rituximab