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Based on evidence that low-dose interleukin-2 (IL-2) increases CD4+CD25+FOXP3+ Treg (CD4Treg) cells in patients with graft-versus-host disease, induction of autoimmune tolerance has been proposed as a treatment.1 However, evidence-based guidelines for the management of primary Sjögren’s syndrome (pSS) are lacking.2 Using a modified method of flow cytometry, we aimed to revaluate the exact levels of Th17 and CD4Treg cells in the peripheral blood (PB) of patients with pSS and explore the effects of short-term and low-dose IL-2.3 4
A total of 190 patients with pSS (169, treated with immunosuppressants; 21, new-onset (sampled as treated or new pSS patients below)) consented at enrolment to donate PB samples for comprehensive immunophenotyping (see online supplementary table S1 and figure S1). In the study, BD Trucount tubes were used to determine the absolute counts of total CD4+ T cells in the PB, and then, the absolute number of CD4+ T subsets, such as CD4Treg cells, were calculated. Detailed methods and statistical analysis is in online version (see online supplementary text).
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Among the CD4+ T subsets in the PB of the healthy control group, Th1 cells had the highest absolute number, and CD4Treg cells were sixfold more abundant than Th17 cells (see online supplementary table S3 and figure 1A–D). Both treated and new pSS patients had significantly fewer absolute CD4Treg cells in their PB (p<0.01) than healthy patients (see figure 1C). CD4Treg cells were the only cell subset with a significant difference in absolute numbers. Notably, neither the absolute number nor proportion of Th17 cells was increased (figure 1A,B). In addition, no significant changes were found in CD4 +CD25+T cells or the percentage of CD4Treg cells (figure 1F,G).5
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When all patients with pSS were divided into low (0≤ EULAR Sjögren’s syndrome disease activity index (ESSDAI)<5), moderate (5≤ESSDAI≤14) and high (ESSDAI >14) disease activity groups (see online supplementary figure S2), the smallest absolute number of CD4Treg cells in PB were identified in patients with high disease activity (figure 2B). However, no significant difference in levels of Th17 cell was observed among the groups (figure 2A,C).
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After low-dose IL-2 treatment, all CD4 +T cells were increased (see online supplementary figure S3), but CD4Treg cells were greatly amplified (fourfold increase) (see online supplementary figure S5, figure 2E). Although the absolute number of Th17 cells also increased, the ratio of Th17/Treg decreased to normal levels (figure 2D,F). Although no obvious improvement in disease activity was found in IL-2 group compared with non-IL-2 group during short-term observation (supplementary figure S4), we observed significant reductions in glucocorticoid and disease-modifying antirheumatic drugs (DMARDS) usage (unpublished data) during long-term observation. No obviously abnormal indicators of laboratory examination were observed during treatment, except for a few cases of rashes around the injection sites and influenza-like symptoms (see online supplementary tables S5–S7). It is possible that low-dose IL-2 can induce antigen-specific CD4+ Treg cells during the treatment process.1 6
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In conclusion, our study demonstrates that the absolute number of circulating CD4Treg cells in patients with pSS is significantly lower than that in healthy patients; however, the absolute number and proportion of Th17 cells are not significantly different. Notably, low-dose IL-2 treatment restores CD4Treg cells and the ratio of Th17/Treg which are helpful for controlling disease activity.7–10 Our findings strengthen the concept of immunoregulation but not immunosuppression in the treatment of pSS.1
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Ruijie Wu collected the information of outpatients. Qi Wu finished procedures of sampling preparation.
Handling editor Josef S Smolen
Contributors All of the authors were involved in the drafting of the article or critical revision of the important intellectual content, and all of the authors approved the final version to be published.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Ethics Committee of the Second Hospital of Shanxi Medical University.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The data that support the findings of this study are available from the corresponding.