Significant association of CX3CR1+CD8 T cells with aging and distinct clinical features in Sjögren's syndrome and IgG4-related disease.

Objectives: Recent studies have implicated cytotoxic CD4 and CD8 T cells in primary Sjögren's syndrome (pSS) and IgG4-related disease (IgG4-RD), but their association with immune aging and organ-specific clinical features remain unclear. CX3CR1 is expressed on cytotoxic CD4 and CD8 T cells. The aim of this study was to determine associations of peripheral CX3CR1+CD4 and CX3CR1+CD8 T cells with aging and clinical features.

Methods: Whole blood samples were freshly obtained from consecutive patients with active, treatment-naïve pSS (n=57), IgG4-RD (n=54), and healthy individuals (n=40) and analysed by flow cytometry for CX3CR1+CD4 and CX3CR1+CD8 proportions. Associations of those T cells with aging and clinical features were determined.

Results: CX3CR1+CD4 and CX3CR1+CD8 T cells selectively expressed perforin and granzyme B. Proportions of CX3CR1+CD4 and CX3CR1+CD8 T cells were significantly higher in pSS and IgG4-RD than in healthy individuals. Higher proportions of CX3CR1+CD8 T cells were associated with aging in pSS and IgG4-RD but not in healthy individuals. Sex differences were not associated with proportions of CX3CR1+CD8 T cells. Furthermore, patients with pSS with interstitial lung disease showed higher proportions of CX3CR1+CD8 T cells than those without interstitial lung disease. IgG4-RD patients with retroperitoneal fibrosis and/or aortitis exhibited higher proportions of CX3CR1+CD8 T cells compared with those with Mikulicz's disease. Moreover, proportions of CX3CR1+CD8 T cells were decreased following glucocorticoid treatment in paralleled with clinical improvements in IgG4-RD.

Conclusions: CX3CR1+CD8 T cells might be involved in immune aging and distinct clinical phenotypes of patients with pSS or IgG4-RD.