AB0149 PERIPHERAL T HELPER SUBSET PROFILING DIFFERS IN VARIOUS SUBSETS OF IDIOPATHIC INFLAMMATORY MYOSITIS
Authors: A. Anuja, H. Singh, D. Misra, V. Agarwal, L. Gupta
Journal: Annals of the Rheumatic Diseases (2020)

Background: There is dearth of biomarkers in Idiopathic Inflammatory Myositis(IIM) to identify ongoing inflammation in the muscle and distinguish it from inactivity or damage. Objectives: Since myositis is autoantibody mediated and tertiary lymphoid organogenesis (TLO) reported in the diseased muscles, we investigated peripheral blood T helper subset profiling as a reflection of ongoing muscle inflammation. Methods: Twenty-six patients of IIM (ACR EULAR criteria) were compared with 15 healthy controls (HC) and 21 patients with sarcoidosis (Table 1). Peripheral blood mononuclear cells were stained with combinations of antibodies to identify Th1, Th17, Th17.1 and Treg cells after stimulation assays (BD Biosciences). Myositis Specific and Associated autoantibodies were tested by the line immunoassay (Euroimmune, Germany). Table 1. Baseline characteristics of patients with inflammatory myositis Characteristics Demographic details (n, % or median, IQR) Healthy Control (median, IQR) Age 37±25.25 26.0±32 Gender(M:F) 5 vs. 21 12 vs. 3 Diagnosis PM 3 DM 15 OM 4 ASS 4 Disease course Monocyclic 5 Polycyclic 7 Chronic continuous 1 Undefined 13 Clinical Profile Myositis 4 (15.3%) ILD 5 (19.23%) Rash 3 (11.53%) Arthritis 6 (23.07%) Other 16 (23.69) Disease duration (years) 1.3 ± 6.91 Disease activity Active 12 [PM(1), OM(1), ASS(4), DM(5)] Inactive 14 [PM(2),OM(2),ASS(0),DM(8)] Antinuclear Antibodies Positive Nuclear Speckled 9 (34.61%) Homogenous 4 (15.38%) Nucleolar 1 (3.8%) Other 5 (19.23%) Cytoplasmic 3 (11.53%) Negative 4 (15.38%) Myositis Specific Antibodies Positive ARS 2(7.6%) Mi-2 3(11.53%) SAE-1 2(7.6%) NXP2 2(7.6%) MDA5 0 MAA Ku 1(3.8%) dsDNA 0 U1RNP 0 Ro52 4(15.38%) Negative 12(46.15%) Results: All T helper subsets were higher in myositis as compared with healthy controls (figure 1A a-d). Between various IIM subsets, polymyositis had higher Th1 and Treg cells (Figure 1B b, c) while Th17 and Th17.1 cells(c) were higher in Overlap Myositis (Figure 1B a, d) as compared with healthy controls. Patients with sarcoidosis had similar subset profiling as myositis.(Figure 5a-f) Figure 1 A. Representative plot depicting all T helper subsets quantified were higher in myositis as compared with healthy controls1B: Representative plot comparing %T cell subsets in various subsets of myositis with healthy controls showing that % Th1 cells (a) and Tregs (d) are highest in Polymyositis than controls while % Th17 (b) and % Th17.1 cells (c) are higher in Overlap Myositis Patients who were had either arthritis or were positive for myositis specific autoantibodies had higher Th17.1 cells (Figure 3 a(iii) &amp; b(iii)) than those negative for MSA. There was no difference in T cell profile between the various autoantibody subsets (Figure 6a-d). There was no difference in subsets between active and inactive disease although active disease had lower Th1/Treg, Th17/Treg and Th17.1/Treg ratios. Conclusion: T Helper cell subsets are distinct from HC but similar to sarcoidosis patients. However, they differ in various subsets of myositis, suggesting different pathogenic mechanisms are operative. Autoantibody positivity is associated with elevated Th17.1 population suggesting plasticity in TLO which needs to be explored further. However, T cell profiling cannot distinguish active from inactive disease limited predictive potential as a biomarker. Figure 2 A. Comparisons between various phenotypic subsets suggest patients positive for MSA had higher Th17.1 cells (Figure 2A a(iii)) than those negative for MSA. Similarly, patients with arthritis had higher Th17.1 cells(Figure 2A b (iii)). 2B Representative dot plot of T cell subsets ratio (Th1, Th17 &amp; Th17.1) with Treg subsets (a) Th17/Treg ratio observed higher in lower cells in active as compared with inactive disease. 2C Representative dot plot T cell subsets in Sacodosis and myositis2D Representative dot plot comparing percentage of T cell subsets in various antibody subsets of myositis Acknowledgments: The authors thank APLAR for funding Myositis antibody testing. Disclosure of Interests: None declared