Background/Purpose: Dermatomyositis (DM) and polymyositis (PM) are rare chronicinflammatory disorders with significant associated morbidityand mortality despite treatment, characterized by subacute onset of proximal muscle weakness, elevated muscle enzymes, and inflammatory infiltrates on muscle biopsy. Although several hypotheses have been proposed for triggers of inflammation in the diseases, growing evidences have focused on the immune disorders. However, the quantitative changes of lymphocyte subsets in DM/PM are unclear and whether low-dose IL-2 could rebalance the lymphocyte subsets and further benefit to remission disease activity of DM/PM patients is unknown. This study aimed to investigate the quantitative status of peripheral blood lymphocyte subsets in the patients for the exploration of pathogenesis and evaluate the safety and efficacy of low-dose IL-2 therapy in patients with DM/PM.

Methods: From February 2016 to October 2018, total 147 patients with PM/DM and 128  gender and age matched healthy individuals were enrolled in this study. The absolute numbers of T, B, NK, CD4+T, CD8+T, Th1, Th2, Th17 and Treg cells in peripheral blood of these individuals were detected by flow cytometry combined with standard absolute counting beads. Patients in IL-2 group (n=31) were not only given traditional treatments, but injected subcutaneously human IL-2 (aldesleukin) at 50 WIU per day for a 5-day course. The demographic features, clinical manifestations and laboratory indicators were compared before and after the treatment.

Results: Patients with PM/DM had lower levels of Treg cells as well as T, CD4+T, CD8+T, Th1, Th2, and Th17 compared with those of the healthy controls (P < 0.05), which was correlated with disease activity(P < 0.05). After IL-2 administration, the absolute numbers of peripheral lymphocyte subsets in patients were significantly increased (P < 0.05), leading to a better remission compared with the patients received conventional therapy (P < 0.05).

Conclusion: The difference status of peripheral lymphocyte subsets, especially Tregs, between PM/DM patients and healthy individuals suggests that lymphocyte subsets may be involved in and play an important role in the pathogenesis of patients. Low-dose IL-2 can effectively increase the level of Treg cells as well as other lymphocytes to some degree and maintain the immunologic balance, which may help for PM/DM patients’ symptoms remission without over-treatment and evaluated side effect. But long-term benefits of IL-2 therapy are required to further study.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/multiple-subpopulations-of-lymphocytes-were-absolutely-decreased-in-dermatomyositis-polymyositis-patients-and-restored-by-low-dose-il-2/