Background/Purpose:

Heavy and light chain gene usage and mutational analyses of the Ig variable regions (V-regions) enable the identification of gene usage within B cell populations. Within the context of antibody secreting cells (ASC) isolated from the minor salivary glands of Sjogren’s syndrome (SS) patients it may give clues to the loss of tolerance that leads to the genesis of autoreactive cells described in these patients.

Methods:

Fourteen subjects were included in this study. Each had symptomatic dry eyes and mouth; 8 subjects met American/European Consensus Group (AECG) primary SS criteria and 1 subject also met the American College of Rheumatology criteria for SLE. Six subjects that did not meet the SS classification criteria (DNMC) served as sicca controls. Labial salivary glands were collected, ASCs were isolated and single-cell sorted using a new method that allows for probing of both kappa and lambda light chains within in the same single cells in rare populations. Cells were sequenced and analyzed for V-region gene usage.

Results:

We identified a total of 83 unique heavy/light chain pairs from the SS patient group and 21 from the DNMC control group. No significant differences in the VH- or JH- gene-family usage were noted between SS or DNMC. The Ig V_H family usage in both the SS patient and DNMC control groups was dominated by the V_H3 and V_H4 gene families and J_H4 was the predominant J_H gene family used by both groups. The light chain analysis revealed that kappa variable region (Vκ) gene families, Vκ1 and Vκ3, were the most frequently used in both groups. The kappa joining (Jκ) gene analysis revealed that J-genes, Jκ-1 through Jκ-5, were represented in sequences from both groups. The light chain sequence analyses also revealed the incidence of secondary light chain editing in the sequences from 2 pSS subjects and one DNMC, indicated by clonally related heavy chains with different light chain usage. These light chain sequences were unique and not found in any of the other pairs utilized by any of the other subjects. In addition, allelic inclusion, or 1 heavy chain with 2 distinct light chains within the same cell, was identified in 2 instances from the ASCs isolated from one pSS patient. In each case, both a kappa and a lambda light chain sequence were amplified from the same cell.

Conclusion:

In summary, we have developed an improved method for the isolation, characterization and mAb production for rare B cells populations, which has provided data suggesting ASC light chain editing and allelic inclusion not previously reported in SS.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/secondary-light-chain-editing-and-allelic-inclusion-in-antibody-secreting-cells-from-the-minor-salivary-gland/