SAT0357 LEVELS OF PERIPHERAL LYMPHOCYTE SUBPOPULATIONS IN PATIENTS WITH ANKYLOSING SPONDYLITIS AND THEIR CHANGES AFTER RECEIVING IMMUNOREGULATORY COMBINATION THERAPIES

Background: Ankylosing spondylitis is an immune-mediated inflammatory disease involving of the axial skeleton, joints, and entheses 1 . Although the homeostatic balance of effector T cells (Teffs) and regulatory T cells (Tregs) is considered to play an important role in the pathogenesis of ankylosing spondylitis(AS) 2 , it is unclear whether the levels of peripheral blood lymphocyte subpopulations in patients with ankylosing spondylitis are abnormal or not. Objectives: To explore the differences of lymphocyte subpopulations of peripheral blood (PB) between AS patients and healthy controls (HCs), and further evaluate the therapeutic effect of immunoregulatory drugs on the lymphocyte subpopulations. Methods: Total 1141 patients with AS and 206 healthy individuals were enrolled in the study and donated their blood to measure the levels of T, B, NK, CD4 + T, CD8 + T, Th1, Th2, Th17 and Tregs by flow cytometry combined with standard absolute counting beads. And 456 patients received immunoregulatory combination treatments which includes low-dose interleukin-2, rapamycin, metformin, retinoic acid etc. and donated their PB after the therapies. Data were expressed as mean ± standard deviation to the distribution. Independent-samples T test and paired-samples T test were applied. P value <0.05 were considered statistically significant. Results: Compared with HCs, AS patients had a lower absolute number of Tregs but higher numbers of peripheral T, B, CD4 + T, CD8 + T and Th17 cells ( P <0.05). Further, there was a significant increase in the percentage of B, CD4 + T and the ratios of Teffs/Tregs such as Th1/Tregs, Th2/Tregs and Th17/Tregs compared with HCs ( P <0.05)(Figure 1). Although, after receiving the immunoregulatory combination treatments, the absolute numbers of various peripheral lymphocyte subpopulations such as T, B, NK, CD4 + T, CD8 + T, Th1, Th17 and Tregs and the percentage of Tregs, Th1 and CD8 + T significantly increased ( P <0.05), the ratios of Th2/Tregs significantly decreased ( P <0.05)(Figure 2), suggesting a rebalance of immune systems. Conclusion: The insufficiency of Tregs may involve in pathogenesis of AS. Immunoregulatory combination therapies could promote the proliferation of Tregs as well as other lymphocytes to some degree, which may be a new target for AS treatment. References: [1]van der Heijde D, Song IH, Pangan AL, et al. Efficacy and safety of upadacitinib in patients with active ankylosing spondylitis (SELECT-AXIS 1): a multicentre, randomised, double-blind, placebo-controlled, phase 2/3 trial. Lancet 2019;394(10214):2108-17. doi: 10.1016/S0140-6736(19)32534-6 [published Online First: 2019/11/17] [2]Xu D, Fan J, Chen Q, et al. OP0028 Low dose IL-2 therapy can recovery TH17/TREG cell balance in patients with ankylosing spondylitis. Oral Presentations, 2017:63.1-63. Disclosure of Interests: None declared