Immunohistochemical analysis as a means to predict responsiveness to rituximab treatment.
OBJECTIVE
Anti-CD20-mediated B cell depletion with rituximab is a new and effective therapy for rheumatoid arthritis (RA). Although B cells in peripheral blood (PB) are consistently depleted in all patients, the clinical effects are more heterogeneous, possibly related to differences in the depleting effects of lymphoid or solid tissues. The aim of this study was to investigate B cell depletion in different compartments (PB, bone marrow, and synovium) and determine predictive variables for responsiveness to rituximab therapy.


METHODS
Before and 12 weeks after rituximab treatment, samples of PB, bone marrow, and synovium were collected from 25 patients with RA refractory to disease-modifying antirheumatic drugs and tumor necrosis factor-blocking agents. CD19+ and CD20+ B cells in PB and bone marrow were measured by flow cytometric analysis, whereas CD79a+ and cytoplasmic CD20+ B cells in the synovium were stained by immunohistochemistry. The effects of rituximab on serum Ig and autoantibodies were measured by enzyme-linked immunosorbent assay.


RESULTS
Rituximab effectively depleted the CD20+ subset of B cells in the PB, bone marrow, and synovium of RA patients. Rituximab significantly reduced autoantibody production (anti-citrullinated protein antibodies [ACPAs] and rheumatoid factor [RF]), in part due to a nonspecific decrease in total Ig production. Importantly, positivity for circulating ACPA IgM, in combination with a high infiltration of CD79a+ B cells in the synovium, but not of CD138+ plasma cells, was a predictor of clinical outcome after rituximab treatment. ACPA IgM titers were independently associated with synovial infiltration of CD20-,CD79a+ B cells, but not with CD138+ plasma cells.


CONCLUSIONS
These data provide novel insights into the mechanisms of CD20-mediated B cell depletion in the lymphoid and solid tissues of RA patients and suggest a pivotal role for ACPA IgM-producing plasmablasts in RA.
Leiden University Medical Center, Leiden, The Netherlands.
Y K Onno
YK
Teng
E W Nivine
EW
Levarht
Mojtaba
M
Hashemi
Ingeborg M
IM
Bajema
René E M
RE
Toes
Tom W J
TW
Huizinga
Jacob M
JM
van Laar
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000378:metabolism; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy* / Q000473:pathology*; D001323:Autoantibodies / Q000097:blood; D001402:B-Lymphocytes / Q000276:immunology / Q000473:pathology*; D001853:Bone Marrow / Q000276:immunology / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D000069283:Rituximab; D013583:Synovial Membrane / Q000276:immunology / Q000473:pathology; D016896:Treatment Outcome
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D018501:Antirheumatic Agents; D001323:Autoantibodies; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D000069283:Rituximab