Identification of Novel CD4+ T Cell Subsets in the Target Tissue of Sjögren’s Syndrome and Their Differential Regulation by the Lymphotoxin/LIGHT Signaling Axis

Abstract

Despite being one of the most common rheumatologic diseases, there is still no disease-modifying drug for primary Sjögren's syndrome (pSS). Advancing our knowledge of the target tissue has been limited by the low dimensionality of histology techniques and the small size of human salivary gland biopsies. In this study, we took advantage of a molecularly validated mouse model of pSS to characterize tissue-infiltrating CD4 T cells and their regulation by the lymphotoxin/LIGHT signaling axis. Novel cell subsets were identified by combining highly dimensional flow and mass cytometry with transcriptomic analyses. Pharmacologic modulation of the LTβR signaling pathway was achieved by treating mice with LTβR-Ig, a therapeutic intervention currently being tested in pSS patients (Baminercept trial NCT01552681). Using these approaches, we identified two novel CD4 T cell subsets characterized by high levels of PD1: Prdm1 effector regulatory T cells expressing immunoregulatory factors, such as Il10, Areg, Fgl2, and Itgb8, and Il21 effector conventional T cells expressing a pathogenic transcriptional signature. Mirroring these observations in mice, large numbers of CD4PD1 T cells were detected in salivary glands from Sjögren's patients but not in normal salivary glands or kidney biopsies from lupus nephritis patients. Unexpectedly, LTβR-Ig selectively halted the recruitment of PD1 naive, but not PD1, effector T cells to the target tissue, leaving the cells with pathogenic potential unaffected. Altogether, this study revealed new cellular players in pSS pathogenesis, their transcriptional signatures, and differential dependency on the lymphotoxin/LIGHT signaling axis that help to interpret the negative results of the Baminercept trial and will guide future therapeutic interventions.

BAFF overexpression increases lymphocytic infiltration in Sjögren's target tissue, but only inefficiently promotes ectopic B-cell differentiation

“…The second limitation resides in the duration of the study which was terminated when mice reached 16 weeks of age. At this time-point, NOD mice have a well-established immune infiltration that is stable in terms of cellular composition and number of infiltrating cells [36]. Nonetheless, one cannot exclude that longer exposure to increased BAFF levels could further increase the frequency and number of GC B cells within the glandular tissue.…”

“…In this study, we aimed at answering this question using the NOD mouse model of pSS, which is one of the best-studied and validated models of pSS [41]. Specifically, integrated analysis of publically-available mouse and human pSS datasets showed that 58% of the human pSS transcriptional gene signature (derived from the analysis of parotid and minor salivary glands from pSS patients) was upregulated in the target tissue from 16-week old male NOD mice [36], indicating that the NOD strain is a relevant model to study the human disease from a molecular standpoint. Nonetheless, this model does not recapitulate all features of the human disease.…”

“…Given that the exocrine tissue of both pSS patients and the NOD mouse model share 58% of their transcriptional profiles, which are publically-available, curated and readily available as gene lists [36], one strategy for future studies will be to focus on the proinflammatory factors uniquely expressed in the target tissue from pSS patients and lacking in the NOD target tissue to identify putative pathogenic factors driving ectopic B cell differentiation in pSS.…”

“…Figure 2, panel A), revealing their transcriptional proximity and confirming the follicular nature of glandular B cells. In contrast, glandular CD4 + T cells clustered away from their splenic counterparts, reflecting a significant transcriptional divergence which is analyzed in detail in a companion manuscript [36]. Lacrimal gland-infiltrating B cells expressed accordingly signature genes of follicular B cells such as Cd55, Dpp4, S1pr1, Sell, Zfp318 whereas GC-specific genes such as Aicda, Ccna2, Mybl1, Ncapg, Stil or Top2a were either not expressed or expressed at lower levels in lacrimal gland B cells than in splenic B cells (Suppl.…”

RNA-Seq and CyTOF immuno-profiling of regenerating lacrimal glands identifies a novel subset of cells expressing muscle-related proteins

“…Mass cytometry has been used to characterize immune subsets in the target tissue and blood of both mouse models of Sjögren’s syndrome and patients with primary Sjögren’s syndrome [9, 10]. RNA-Seq transcriptomic analyses were reported in various diseases, such as Crohn’s disease, renal injury, chronic periodontitis, and many others [11–14].…”