Background:Dermatomyositis and polymyositis (DM/PM) are associated with muscle weakness and inflammatory infiltration within the skeletal muscle. The numerical and functional defects of immune cells, due to long-term uses of glucocorticoids and disease-modifying anti-rheumatic drugs (DMARDs) together with immune disturbances associated with disease itself, lead to high risks in opportunistic infections, such as Epstein-Barr virus (EBV) and cytomegalovirus (CMV).1-2We want to observe changes of

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... eripheral lymphcytessubsets in PM/DM patients with EBV and/or CMV infection,especially whether there is imblance between Th17 and Treg cells.Objectives:To investigate the characteristics of peripheral lymphocyte subsets in PM/DM with EBV and/or CMV infection, especially the Th17 and Treg cells.Methods:From February 2016 to November 2019, PM/DM patients with EBV and/or CMV viremia (infection group, n=34) and without infection (non-infection group, n=31) as well as healthy adult controls (n=20) were enrolled in our study. Absolute numbers of total T, total B, NK, CD4 + T, CD8 + T cells, and CD4 + T subsets (Th1, Th2, Th17 and Treg cells) in peripheral blood by flow cytometry combined with standard absolute counting beads.Results:(1) Compared with PM/DM patients without infection, 34 PM/DM patients with EBV and/or CMV infection, including 12 patients with EBV, 20 patients with CMV, 2 patients combined EBV and CMV, the absolute number of total T lymph cells (P=0.019), total B lymph cells (P=0.037), NK cells (P=0.033), CD4 + T cells (P=0.000), Th1 cells (P=0.014), Th2 cells (P=0.003), Th17 cells (P=0.003), Treg cells (P=0.004) lower than its of (P=0.003) patients without infection, the absolute number of CD8 + T cells (P=0.427) has no obvious difference between them.(2) And its the absolute number of total T lymph cells (P=0.000), total B lymph cells (P=0.003), NK cells (P=0.000), CD4 + T cells (P=0.000), CD8 + T cells (P=0.006), Th1 cells (P=0.000), Th2 cells (P=0.001), Th17 cells (P=0.000) and Treg cells (P=0.000) significantly lower than healthy control.(3) Compared with the healthy control,the absolute number of total T lymph cells (P=0.000), NK cells (P=0.000), CD4 + T cells (P=0.031), CD8 + T cells (P=0.000), Th1 cells (P=0.002), Th2 cells (P=0.031), and Treg cells (P=0.000) in PM/DM without infection evidently lower, but there is no siginificant difference in absolute number of total B lymph cells (P=0.19) and Th17 cells (P=0.171).Conclusion:We show that the absolute number of peripheral blood lymphocytes and CD4+T subsets in patients with PM/DM with EBV and/or CMV viremia is further reduced. In addition to Treg cells, a decrease in Th17 cells may also be an important feature of EBV and/or CMV infection in DM/PM. These cell reductions may be the cause and risk indicator of viral infections.References:[1]Yang X, Hao Y, Zhang X, et al. Mortality of Chinese patients with polymyositis and dermatomyositis. Clin Rheumatol. 2020 Jan 4. doi: 10.1007/s10067-019-04910-w. [Epub ahead of print]. PMID: 31902027[2]Matsushita T,Kobayashi T, Kano M, et al. Elevated serum B-cell activating factor levels in patients with dermatomyositis: Association with interstitial lung disease. J Dermatol.2019:46:1190-6. doi:10.1111/1346-8138.15117Figure.Absolute numbers of peripheral lymphocyte subsets between healthy controls and patients were assessed by fow cytometry using oneplatform method. PM/DM infection group (n=34), PM/DM non- infection group(n=31)and healthy control group (n = 20).(*p<0.05, **p<0.01, ***p<0.001)Disclosure of Interests:None declared