RT Journal Article SR Electronic T1 Impact of IL-6 receptor inhibition on human memory B cells in vivo: impaired somatic hypermutation in preswitch memory B cells and modulation of mutational targeting in memory B cells JF Annals of the Rheumatic Diseases JO Ann Rheum Dis FD BMJ Publishing Group Ltd and European League Against Rheumatism SP 1507 OP 1510 DO 10.1136/ard.2010.141325 VO 70 IS 8 A1 Muhammad, Khalid A1 Roll, Petra A1 Seibold, Thomas A1 Kleinert, Stefan A1 Einsele, Hermann A1 Dörner, Thomas A1 Tony, Hans-Peter YR 2011 UL http://ard.bmj.com/content/70/8/1507.abstract AB Objective Interleukin 6 (IL-6) receptor (IL-6R) inhibition by tocilizumab is a novel anti-inflammatory therapy for rheumatoid arthritis (RA) patients. As IL-6 is a late differentiation factor of B cells the authors asked if IL-6R inhibition impacts on the mutational differentiation of human memory B-cell antigen receptors in vivo. Methods 1733 immunoglobulin receptors (IgR) of single cell sorted preswitch and postswitch memory B cells were prospectively analysed from 11 RA patients under IL-6R inhibition (7 patients) or tumour necrosis factor (TNF) inhibition (4 patients). Results The results show a reduced mutational frequency in IgR of preswitch memory B cells (p=0.0001) during week 12, week 24 and 1 year of tocilizumab therapy. Mutational hotspot RGYW/WRCY motifs indicated significantly decreased targeting (p<0.05) in preswitch and postswitch memory B cells. Anti-TNFα therapy had no effect on mutational frequency and mutational hotspot targeting motifs in memory B-cell subsets. Conclusions These data suggest that preswitch and postswitch memory B cells are susceptible to IL-6R inhibition in vivo. Acquisition of mutations was substantially altered in preswitch memory B cells, while targeting of mutational hotspots affected preswitch and postswitch memory B cells. The results indicate that preswitch and postswitch memory B cells have a differential dependence on the IL-6/IL-6R system for differentiation, which can be influenced by tocilizumab in vivo.