Modulation of molecular imprints in the antigen-experienced B cell repertoire by rituximab.
OBJECTIVE
Transient B cell depletion by rituximab has recently gained more importance in the treatment of rheumatic disorders. Nevertheless, little is known about the reemerging B cells. We analyzed dynamic changes in the repopulating B cells, particularly the postswitch B cells, and studied the mutational patterns of Ig genes in antigen-experienced B cells.


METHODS
Five patients with active rheumatoid arthritis (RA) were treated with rituximab. In 3 patients, B cell receptor (BCR) gene analysis was performed before treatment and during B cell recovery using genomic DNA. In 2 patients, B cell subsets were studied during the early recovery phase using single-cell technology. For comparison, immunophenotyping of B cell subsets was performed.


RESULTS
Early B cell recovery was marked by a relatively expanded population of highly mutated B cells, which were correlated with B cells with a plasmablast phenotype on comparative immunophenotyping. Analysis of the mutational pattern in these cells revealed increased RGYW/WRCY (where R = A/G, Y = C/T, and W = A/T) hotspot targeting (44% before rituximab versus 59% after) and elevated ratios of replacement to silent mutations within the complementarity-determining regions in Ig genes (1.87 before rituximab versus 2.67 after; P < or = 0.0025).


CONCLUSIONS
Our findings show that rituximab leads to qualitative changes in the imprints of highly mutated, antigen-experienced BCRs, representing the result of selection, whereas molecular processes such as Ig V rearrangements are not affected by this treatment.
Palanichamy
Arumugam
A
University of Würzburg, Würzburg, Germany.
Roll
Petra
P
Theiss
Regina
R
Dörner
Thomas
T
Tony
Hans-Peter
HP
D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D018941:Antigens, CD19 / Q000378:metabolism; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy* / Q000276:immunology*; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D005434:Flow Cytometry; D015322:Gene Rearrangement, B-Lymphocyte / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007072:Immunoglobulin D / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics; D016130:Immunophenotyping; D008875:Middle Aged; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D000069283:Rituximab
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018941:Antigens, CD19; D018501:Antirheumatic Agents; D007072:Immunoglobulin D; D007135:Immunoglobulin Variable Region; D011947:Receptors, Antigen, B-Cell; D000069283:Rituximab