Background Characteristic changes in the distribution of peripheral B cell subsets and differences in use of immunoglobulin-variable region genes are features of Sjögren's Syndrome (SS). Studies on Hepatitis C virus infected (HCV+) mixed Cryoglobulinemia (MC) patients have revealed B cell clonal expansion expressing stereotypical Rheumatoid Factor (RF) encoded by the immunoglobulin genes VH1-69 and Vk 3-20. G6 antibody specific for VH1-69 can identify the RF- expressing B cells in HCV+MC patients.Since some SS patients have been known to develop lymphomas bearing VH1-69 encoded antibodies, we hypothesized that SS patients might have clonal expansions of VH1-69-bearing B cells.
Objectives Identify B lymphocyte characteristics in patients with Sjogren's syndrome
Methods We obtained blood samples from 13 patients diagnosed with SS at a teaching hospital rheumatology clinic, serving a large inner city population. Further processing of the blood samples from these patients was done at Rockefeller University and the Peripheral Blood Mononuclear Cells (PBMCs) were cryopreserved. Fluorescent- labeled Ro/SS-A (52,60kDA) and La-SS-B antigens were obtained. The purpose was to label B cells that make SS-A antibody so they could be seen by flow cytometry.
Results Preliminary flow cytometric analysis of B cells in 8 of the blood samples showed a B cell phenotype different from that seen in HCV-associated MC. The memory B cells were high in CD-21, unlike those seen in HCV-associated MC. Few VH1-69 + B cells were seen in 4/8 patients analyzed. The other blood samples showed very few cells binding SS-A.
Conclusions Unraveling the association between autoimmunity and lympoproliferation in SS patients will have clinical value, and B cell gene expression data may be able to predict susceptibility to lymphoma in these individuals. The abnormally expanded B cells should be studied at the transcriptional, proteomic and functional levels. The lack of direct comparison between the B cell repertoire in the blood and that in the parotids and/or minor salivary glands has prevented drawing of firm conclusions. The long term goal would be to clone, sequence and characterize autoantibodies produced in SS.
Disclosure of Interest : None declared
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