Generation mechanism of RANKL(+) effector memory B cells: relevance to the pathogenesis of rheumatoid arthritis.
BACKGROUND
The efficacy of B cell-depleting therapies for rheumatoid arthritis underscores antibody-independent functions of effector B cells such as cognate T-B interactions and production of pro-inflammatory cytokines. Receptor activator of nuclear factor κB ligand (RANKL) is a key cytokine involved in bone destruction and is highly expressed in synovial fluid B cells in patients with rheumatoid arthritis. In this study we sought to clarify the generation mechanism of RANKL(+) effector B cells and their impacts on osteoclast differentiation.


METHODS
Peripheral blood and synovial fluid B cells from healthy controls and patients with rheumatoid arthritis were isolated using cell sorter. mRNA expression of RANKL, osteoprotegerin, tumor necrosis factor (TNF)-α, and Blimp-1 was analyzed by quantitative real-time polymerase chain reaction. Levels of RANKL, CD80, CD86, and CXCR3 were analyzed using flow cytometry. Functional analysis of osteoclastogenesis was carried out in the co-culture system using macrophage RAW264 reporter cells.


RESULTS
RANKL expression was accentuated in CD80(+)CD86(+) B cells, a highly activated B-cell subset more abundantly observed in patients with rheumatoid arthritis. Upon activation via B-cell receptor and CD40, switched-memory B cells predominantly expressed RANKL, which was further augmented by interferon-γ (IFN-γ) but suppressed by interleukin-21. Strikingly, IFN-γ also enhanced TNF-α expression, while it strongly suppressed osteoprotegerin expression in B cells. IFN-γ increased the generation of CXCR3(+)RANKL(+) effector B cells, mimicking the synovial B cell phenotype in patients with rheumatoid arthritis. Finally, RANKL(+) effector B cells in concert with TNF-α facilitated osteoclast differentiation in vitro.


CONCLUSIONS
Our current findings have shed light on the generation mechanism of pathogenic RANKL(+) effector B cells that would be an ideal therapeutic target for rheumatoid arthritis in the future.
['Ota|Yuri|Y|', 'Niiro|Hiroaki|H|', 'Ota|Shun-Ichiro|S|', 'Ueki|Naoko|N|', 'Tsuzuki|Hirofumi|H|', 'Nakayama|Tsuyoshi|T|', 'Mishima|Koji|K|', 'Higashioka|Kazuhiko|K|', 'Jabbarzadeh-Tabrizi|Siamak|S|', 'Mitoma|Hiroki|H|', 'Akahoshi|Mitsuteru|M|', 'Arinobu|Yojiro|Y|', 'Kukita|Akiko|A|', 'Yamada|Hisakata|H|', 'Tsukamoto|Hiroshi|H|', 'Akashi|Koichi|K|']
D000328:Adult D000368:Aged D000369:Aged, 80 and over D001172:Arthritis, Rheumatoid D016175:B-Lymphocyte Subsets D002454:Cell Differentiation D002469:Cell Separation D018920:Coculture Techniques D005260:Female D006801:Humans D007156:Immunologic Memory D008297:Male D008875:Middle Aged D010010:Osteoclasts D053245:RANK Ligand D060888:Real-Time Polymerase Chain Reaction D055815:Young Adult
B cells Rheumatoid arthritis RANKL