Presence of a population of CD20+, CD38- B lymphocytes with defective proliferative responsiveness in the synovial compartment of patients with rheumatoid arthritis.
OBJECTIVE
To provide a comprehensive understanding of the humoral immune response that takes place at the site of inflammation in rheumatoid arthritis (RA), we studied the functional properties of synovial B cells. In particular, the response to various modes of mitogen stimulation was investigated.


METHODS
Purified synovial fluid (SF) B cells were cultured in the presence of CD40 ligand (CD40L)-expressing fibroblasts and cytokines, activated T cells, or phorbol myristate acetate (PMA)/ionomycin. Proliferation was determined by 3H-thymidine incorporation. Release of intracellular calcium was studied by flow cytometry.


RESULTS
The inflamed joints of RA patients contained a population of CD20+,CD38- B cells with dramatically impaired mitogen responsiveness. Although the Ig-producing capacity was intact, these cells failed to proliferate in response to (a) CD40 in the presence of interleukin-2 (IL-2) and IL-10, (b) activated T cells, or (c) stimulation via the B cell receptor. Moreover, SF CD20+,CD38- B cells revealed a defective B cell receptor-induced Ca2+ influx, reminiscent of anergic B cells. Release of intracellular Ca2+ by ionomycin in the presence of the protein kinase C activator PMA did not restore the proliferative capacity. These findings indicate blockades in the proximal and distal intermediates involved in mitogen signaling.


CONCLUSIONS
SF CD20+,CD38- B cells have functionally impaired proliferative responsiveness. The capacity of these cells to respond to activation by the production of Ig supports the notion that these cells might serve as Ig-producing effector cells and, as such, play a role in the pathophysiology of RA.
Reparon-Schuijt
C C
CC
Leiden University Medical Center, The Netherlands.
van Esch
W J
WJ
van Kooten
C
C
Ezendam
N P
NP
Levarht
E W
EW
Breedveld
F C
FC
Verweij
C L
CL
D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000328:Adult; D000368:Aged; D015703:Antigens, CD; D018951:Antigens, CD20 / Q000032:analysis*; D000943:Antigens, Differentiation / Q000032:analysis*; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D001402:B-Lymphocytes / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D019013:CD40 Antigens / Q000276:immunology; D023201:CD40 Ligand / Q000494:pharmacology; D020013:Calcium Signaling / Q000276:immunology; D002273:Carcinogens / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000096:biosynthesis; D016753:Interleukin-10 / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins; D008875:Middle Aged; D009244:NAD+ Nucleosidase / Q000032:analysis*; D010084:Oxidation-Reduction; D013582:Synovial Fluid / Q000166:cytology / Q000276:immunology; D013583:Synovial Membrane / Q000276:immunology* / Q000473:pathology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D015703:Antigens, CD; D018951:Antigens, CD20; D000943:Antigens, Differentiation; D019013:CD40 Antigens; D002273:Carcinogens; D007136:Immunoglobulins; D007376:Interleukin-2; D007476:Ionophores; D008562:Membrane Glycoproteins; D016753:Interleukin-10; D023201:CD40 Ligand; D015759:Ionomycin; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; D009244:NAD+ Nucleosidase; D051997:ADP-ribosyl Cyclase 1; D013755:Tetradecanoylphorbol Acetate