Low number of memory B cells in the salivary glands of patients with primary Sjögren's syndrome

Abstract

We have previously shown that patients with primary Sjögren's Syndrome (pSS) show a significant reduction of autoantigen specific CD27⁺ memory B cells and an abnormally elevated level of autoantibody producing plasma cells in peripheral blood (PB) compared to controls. Because both memory B cells and plasma cells have been detected in salivary glands (SG) of pSS patients, we aimed to study the B cell pattern in SG biopsies. Double immunohistochemical staining of CD20 and CD27 was carried out on paraffin-embedded SG tissue from 10 pSS patients to distinguish CD20⁺/CD27⁺ memory B cells, and identify the CD20⁺ glandular B cell zones (BCZ). Given that plasma blasts and plasma cells are CD27⁺⁺ and CD20⁻ , additional CD138 single staining of serial sections allowed the distinction of CD27⁺⁺/CD138⁻ plasma blasts located within the BCZ from CD27⁺⁺/CD138⁺ plasma cells that were found mostly on the periphery of the BCZ and also observed interstitially. Both BCZ and the memory B cell populations were then quantified. Contrary to what has been reported earlier through immunoflourescent staining of memory B cells in SG tissue, we have shown that there is a low number of memory B cells located within the glandular BCZ. Plasma blasts and plasma cells, however, were more abundant in the SG. Together our findings suggest that these low numbers of memory B cells in both PB and SG of pSS patients may be the result of activation of these cells into plasma cells at the site of inflammation.

Keywords::

• Autoimmunity
• B cell zones
• memory B cells
• plasma cells
• salivary glands
• Sjögren's syndrome

Acknowledgements

We gratefully acknowledge Professor Johan G. Brun from The Department of Rheumatology, Haukeland University Hospital for providing us with clinical information on the subjects and patients included in the study, Professor Anne Christine Johannessen at Section for Pathology-The Gade Institute for the routine histological assessment of the salivary gland sections and Gunnvor Øijordsbakken for excellent technical assistance.

Declaration of interest: The study was supported by The Faculty of Medicine and Dentistry at the University of Bergen, The Broegelmann Foundation, Western Norway Regional Health Authority, and Astrid og Edvard Riisøens legat. The authors declare that they have no competing interests. The authors alone are responsible for the content and writing of the paper.