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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 Sjogren's Syndrome.

ABSTRACT: OBJECTIVE: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. METHODS: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. RESULTS: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. CONCLUSION: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.

SUBMITTER: Koelsch KA

PROVIDER: S-EPMC6019603 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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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.

Koelsch Kristi A KA Cavett Joshua J Smith Kenneth K Moore Jacen S JS Lehoux Sylvain D SD Jia Nan N Mather Tim T Quadri Syed M S SMS Rasmussen Astrid A Kaufman C Erick CE Lewis David M DM Radfar Lida L Scordino Teresa A TA Lessard Christopher J CJ Kurien Biji T BT Cummings Richard D RD James Judith A JA Sivils Kathy L KL Farris A Darise AD Scofield R Hal RH

Arthritis & rheumatology (Hoboken, N.J.) 20180511 7

<h4>Objective</h4>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 s ...[more]

PMID: 29457375

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Project description:BACKGROUND:The cell-cycle inhibitor and tumor suppressor cyclin dependent kinase inhibitor, p16ink4a, is one of the two gene products of the ink4a/ARF (cdkn2a) locus on chromosome 9q21. Up-regulation of p16ink4a has been linked to cellular senescence, and findings from studies on different mammalian tissues suggest that p16ink4a may be a biomarker of organismal versus chronological age. OBJECTIVE:The aim of this study was to examine the immunolocalization pattern of p16ink4a in human labial salivary gland (LSG) tissue, and to analyze whether its expression level in LSGs is a peripheral correlate of cognitive decline in late midlife. METHODS:The present study was a part of a study of causes and predictors of cognitive decline in middle-aged men in a Danish birth cohort. It is based on data from 181 male participants from the Danish Metropolit birth cohort, born in 1953, who were examined for age-associated alterations in cognition, dental health, and morphological and autonomic innervation characteristics of the LSGs. The participants were allocated to two groups based on the relative change in cognitive performance from young adulthood to late midlife. LSG biopsies were analyzed by qRT-PCR for the expression level of p16ink4a. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded sections of LSGs. RESULTS:p16ink4a immunoreactivity was observed in LSG ductal, myoepithelial, and stromal cells, but not in acinar cells. The mean relative expression of p16ink4a in LSGs was higher in the group of participants with decline in cognitive performance. A logistic regression analysis revealed that the relative p16 expression was predictive of the participant's group assignment. A negative correlation was found between relative p16ink4a expression and the participant's standardized regression residuals from early adulthood to late midlife cognitive performance scores. CONCLUSIONS:p16ink4a expression in human LSGs may constitute a potential peripheral correlate of cognitive decline. Human labial salivary glands seem suitable for studies on organismal as opposed to chronological age.

Dataset Information

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 Sjogren's Syndrome.

Publications

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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