Background The cellular characterization of the immune infiltrate in exocrine glands from patients with primary Sjögren's syndrome (pSS) has relied so far on methods with low dimensionality. As a result, our knowledge of cellular events taking place in the exocrine glands of these patients is limited.
Objectives In order to quantify cellular variations associated with pathogenesis, we used here highly multiparametric cytometry by time-of-flight (CyTOF) to analyze diagnostic biopsies from patients with pSS and non-pSS sicca controls.
Methods The CyTOF instrument combines single cell analysis used in flow cytometry with mass spectrometry detection of metal-conjugated antibodies. Using a panel of 36 antibodies, cell populations present in heterogeneous cell suspensions were characterized and correlated with clinical parameters. In parallel, paired formalin-fixed, paraffin embedded sections of labial glands from 15 individuals from this cohort were used to examine anatomic relationships between cell subsets identified by CyTOF.
Results We studied 16 pSS patients and 13 non-pSS sicca controls, among which 81% were anti-SSA+, 44% were anti-SSB+, and 63% had a focus score of 1 or more. In addition to confirming the well-characterized presence of CD4+ T cells and B cells in Sjögren's biopsies, this experimental approach revealed several additional pathologic features, among which are: (a) a dramatic accumulation of CD38++CD27+HLA-DRlow cells (up to 50% of glandular B cells); (b) an unexpected abundance of CD8+ T cells showing marks of activation; (c) the upregulation of HLA-DR on epithelial cells in pSS patients with grades ≥3, which constitutes the first direct evidence of a potential pathological contribution of the epithelium using un-manipulated, ex vivo, primary human cells.
Conclusions The CyTOF instrument is a new tool allowing precise determination of salivary gland subsets, which may generate new mechanistic hypotheses on pathogenesis of the disease.
Disclosure of Interest None declared