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Arthritis Rheumatol. 2018 Jul;70(7):1102-1113. doi: 10.1002/art.40458. Epub 2018 May 11.

Evidence of Alternative Modes of B Cell Activation Involving Acquired Fab Regions of N-Glycosylation in Antibody-Secreting Cells Infiltrating the Labial Salivary Glands of Patients With Sjögren's Syndrome.

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University of Oklahoma Health Sciences Center, Oklahoma Medical Research Foundation, and Department of Veterans Affairs Medical Center, Oklahoma City, Oklahoma.
Oklahoma Medical Research Foundation, Oklahoma City.
Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
University of Oklahoma Health Sciences Center and Oklahoma Medical Research Foundation, Oklahoma City.
University of Oklahoma Health Sciences Center, Oklahoma City.
University of Oklahoma College of Dentistry, Oklahoma City.



To better understand the role of B cells, the potential mechanisms responsible for their aberrant activation, and the production of autoantibodies in the pathogenesis of Sjögren's syndrome (SS), this study explored patterns of selection pressure and sites of N-glycosylation acquired by somatic mutation (acN-glyc) in the IgG variable (V) regions of antibody-secreting cells (ASCs) isolated from the minor salivary glands of patients with SS and non-SS control patients with sicca symptoms.


A novel method to produce and characterize recombinant monoclonal antibodies (mAb) from single cell-sorted ASC infiltrates was applied to concurrently probe expressed genes (all heavy- and light-chain isotypes as well as any other gene of interest not related to immunoglobulin) in the labial salivary glands of patients with SS and non-SS controls. V regions were amplified by reverse transcription-polymerase chain reaction, sequenced, and analyzed for the incidence of N-glycosylation and selection pressure. For specificity testing, the amplified regions were expressed as either the native mAb or mutant mAb lacking the acN-glyc motif. Protein modeling was used to demonstrate how even an acN-glyc site outside of the complementarity-determining region could participate in, or inhibit, antigen binding.


V-region sequence analyses revealed clonal expansions and evidence of secondary light-chain editing and allelic inclusion, of which neither of the latter two have previously been reported in patients with SS. Increased frequencies of acN-glyc were found in the sequences from patients with SS, and these acN-glyc regions were associated with an increased number of replacement mutations and lowered selection pressure. A clonal set of polyreactive mAb with differential framework region 1 acN-glyc motifs was also identified, and removal of the acN-glyc could nearly abolish binding to autoantigens.


These findings support the notion of an alternative mechanism for the selection and proliferation of some autoreactive B cells, involving V-region N-glycosylation, in patients with SS.

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