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Detection of RANKL produced by synovial B cells of RA patients

Receptor activator of nuclear factor kappa-B ligand (RANKL) is important in bone metabolism, which is the key cytokine driving bone destruction. The expression of RANKL can be detected by flow cytometry. Peripheral blood and synovial fluid mononuclear cells were co-labelled with anti-CD19 and either isotype matched control or anti-RANKL antibody.

The results showed that only a very small proportion of B cells expressed RANKL in the peripheral blood of rheumatoid arthritis (RA) patients, a significantly higher proportion of B cells from synovial fluid samples expressed RANKL on their surface. This is the first study to report that B cells contribute to RANKL production in the inflamed rheumatoid joint, which may suggest that depletion of RANKL-expressing B cells may contribute to the inhibition of bone erosion by rituximab.

Reference: Lorraine Yeo, Kai-Michael Toellner, Mike Salmon, Andrew Filer, Christopher D Buckley, Karim Raza, Dagmar Scheel-Toellner. Cytokine mRNA profi ling identifi es B cells as a major source of RANKL in rheumatoid arthritis. British Medical Journal 2011, doi:10.1136/ard.2011.153312