Role of Innate Lymphoid Cells in primary SJÖgren*s syndrome salivary gland damage

One of the most commonly recognized characteristics of pSS, yet most poorly
understood, is that of hyposalivation. Long before presence of lymphocytic foci
that are often used to characterize pSS, when SG morphology still looks
histologically perfect, production of saliva production already drops. We have
recently shown that in the long term, this persistent hyposalivation is most
probably caused by senescence of tissue resident salivary gland stem cells
(SGSCs), in combination with the ongoing inflammatory process. Our data suggest
that proinflammatory cytokines induce this premature SGSC senescence. The
cellular origin of these proinflammatory signals remains unresolved, however.
Epithelial cells of the salivary gland may also be susceptible to signals from
innate lymphoid cells (ILCs) present in the gland, in early pSS. ILCs are a
recently described family of lymphoid effector cells who can best be viewed as
innate homologues of effector T cells, without the need for antigen
presentation via MHC complex for activation. Cytokines secreted by ILCs may
provide the first signal triggering the development of hyposalivation in pSS.

To assess the presence of absence of ILCs in preclinical (early) pSS biopsies
as well as to assess their potential interaction with epithelial cells.

Goal 1. Flow cytometric analysis of processed SG biopsies will generate a hit
list of innate lymphoid cells subsets over or under represented in early pSS
SGs, in comparison with pSS and non-SS sicca controls. Specific immune subsets
that will be examined include intraepithelial CD4+ and CD8+ T cells
(CD103+CD69+), innate lymphoid cells type 1, 2 and 3 and natural killer (NK)
cells. Goal 2 Examine the potential of identified ILCs or other tissue resident
innate immune cell populations for interaction with epithelial cells, in terms
of their transcriptome, single cell RNAseq will be performed on FACS sorted
cell subsets. Goal 3 Probe interaction of ILCs with epithelial cells by
co-culture of FACS-sorted ILC population in transwell culture system with
healthy control SGSCs.

This is a minimal risk study. As mentioned, the biopsy will be part of the
subject*s routine clinical care for diagnostic purposes. The parotid gland
tissue needed for the experiments will be collected simultaneously with the
diagnostic biopsy via the same surgical approach. Taking this extra amount of
tissue, similar to the amount of tissue needed for the diagnostic work-up, will
not increase the morbidity of the diagnostic procedure and will prolong the
routine biopsy procedure with, at most, 30 seconds. Our intervention studies
(rituximab, abatacept treatment) have shown that taking repeated biopsies
from the same parotid gland is not accompanied by increased morbidity of the
surgical procedure. Although the patient has no direct benefit from this study,
there a significant benefits for future pSS patients.