Patients with Primary Sjögren's Syndrome Have Alterations in Absolute Quantities of Specific Peripheral Leucocyte Populations

Abstract

An accurate dissection of peripheral blood enumeration is lacking in primary Sjögren's syndrome (pSS). The purpose of this study was to quantify different leucocyte populations in peripheral blood of patients with pSS. Numbers of specific leucocyte subsets were determined in 86 pSS patients and 74 healthy donors quantifying 21 distinct subtypes by flow cytometry. Subgroups of pSS patients were stratified based on presence of extraglandular manifestations (EGMs) and SSA/SSB autoantibodies. Overall, pSS patients manifested decreased lymphocyte subpopulations compared to healthy donors. Such decreases were more pronounced in SSA/SSB positive patients and patients with EGM. Granulocyte and monocyte subpopulations were increased in pSS patients compared to healthy donors, with the greatest increases in SSA/SSB positive patients. Unsupervised hierarchal clustering based on cell quantities was used to further subgroup the pSS patients into four clusters. One of the clusters characterized by higher concentrations of NKT cells, CD56hi NK cells, CD20⁺ CD38^- B cells and CD8⁺ CD38^- T cells was associated with weaker clinical symptoms than the other clusters, possibly marking a milder disease phenotype. In conclusion, our analyses indicate significant alterations in the cellular profiles of peripheral blood leucocytes in patients with pSS and may help to stratify the patients according to disease severity.