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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.

Author information

1
University of Oklahoma Health Sciences Center, Oklahoma Medical Research Foundation, and Department of Veterans Affairs Medical Center, Oklahoma City, Oklahoma.
2
Oklahoma Medical Research Foundation, Oklahoma City.
3
Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
4
University of Oklahoma Health Sciences Center and Oklahoma Medical Research Foundation, Oklahoma City.
5
University of Oklahoma Health Sciences Center, Oklahoma City.
6
University of Oklahoma College of Dentistry, Oklahoma City.

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.

PMID:
29457375
PMCID:
PMC6019603
DOI:
10.1002/art.40458
[Indexed for MEDLINE]
Free PMC Article

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