Internalization of rituximab and the efficiency of B Cell depletion in rheumatoid arthritis and systemic lupus erythematosus

Arthritis Rheumatol. 2015 May;67(8):2046-55. doi: 10.1002/art.39167.


Objective: Rituximab, a type I anti-CD20 monoclonal antibody (mAb), induces incomplete B cell depletion in some patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), thus contributing to a poor clinical response. The mechanisms of this resistance remain elusive. The purpose of this study was to determine whether type II mAb are more efficient than type I mAb at depleting B cells from RA and SLE patients, whether internalization influences the efficiency of depletion, and whether Fcγ receptor type IIb (FcγRIIb) and the B cell receptor regulate this internalization process.

Methods: We used an in vitro whole blood B cell-depletion assay to assess the efficiency of depletion, flow cytometry to study cell surface protein expression, and surface fluorescence-quenching assays to assess rituximab internalization, in samples from patients with RA and patients with SLE. Paired t-test or Mann-Whitney U test was used to compare groups, and Spearman's rank correlation test was used to assess correlation.

Results: We found that type II mAb internalized significantly less rituximab than type I mAb and depleted B cells from patients with RA and SLE at least 2-fold more efficiently than type I mAb. Internalization of rituximab was highly variable between patients, was regulated by FcγRIIb, and inversely correlated with cytotoxicity in whole blood B cell-depletion assays. The lowest levels of internalization were seen in IgD- B cells, including postswitched (IgD-CD27+) memory cells. Internalization of type I anti-CD20 mAb was also partially inhibited by anti-IgM stimulation.

Conclusion: Variability in internalization of rituximab was observed and was correlated with impaired B cell depletion. Therefore, slower-internalizing type II mAb should be considered as alternative B cell-depleting agents for the treatment of RA and SLE.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antibodies, Monoclonal / metabolism
  • Antibodies, Monoclonal / pharmacology
  • Antibodies, Monoclonal, Humanized / metabolism
  • Antibodies, Monoclonal, Humanized / pharmacology
  • Antibodies, Monoclonal, Murine-Derived / metabolism
  • Antibodies, Monoclonal, Murine-Derived / pharmacology*
  • Antirheumatic Agents / metabolism
  • Antirheumatic Agents / pharmacology*
  • Arthritis, Rheumatoid / immunology*
  • B-Lymphocytes / drug effects*
  • B-Lymphocytes / metabolism
  • Drug Resistance
  • Female
  • Humans
  • In Vitro Techniques
  • Lupus Erythematosus, Systemic / immunology*
  • Male
  • Middle Aged
  • Receptors, IgG / metabolism
  • Rituximab
  • Young Adult


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Antibodies, Monoclonal, Murine-Derived
  • Antirheumatic Agents
  • Fc gamma receptor IIB
  • Receptors, IgG
  • Rituximab
  • obinutuzumab