THU0237 UNCOVERING DIFFERENCES BETWEEN THE SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) AND HEALTHY IMMUNOMES USING MULTI-PARAMETRIC INTERROGATION
Authors: K. Nay Yaung, J. G. Yeo, M. Wasser, P. Kumar, S. P. Tang, S. K. Ng, S. L. Poh, T. Arkachaisri, S. Albani
Journal: Annals of the Rheumatic Diseases (2020)

Background: Systemic lupus erythematosus (SLE) is a complex, systemic autoimmune disease that interferes with the balance between regulation and immunity, resulting in immune system dysfunction. Disease course is unpredictable due to alternating remissions and flares 1 . Disease activity and treatment response are measured with composite scores such as the SLE Disease Activity Index (SLEDAI) 2 . However, disease heterogeneity can impede reliable patient assessments. Mechanistic insights into SLE are required for better assessment. Current studies are mainly descriptive, and a complex disease like SLE is best interrogated with multi-parametric, holistic approaches such as mass cytometry (CyTOF). Objectives: (1)To characterise immune signatures of newly diagnosed SLE patients and in the process: a.Study the roles of B and T cells in SLE b.Gain a holistic understanding of the adaptive immune response (2)To compare immunological profiles of newly diagnosed SLE patients with age-matched healthy controls We hypothesise that significant differences exist between immunomes of newly diagnosed SLE and healthy subjects. Methods: Peripheral blood mononuclear cells (PBMCs) of 5 SLE subjects (median age 125 months) were tested with CyTOF. Data was uploaded to an online analytical platform, the Extended Polydimensional Immunome Characterization (EPIC) discovery tool, for comparison with 51 age-matched controls in its database. Subsequently, normalization and FlowSOM (Flow cytometry analysis by Self-Organising Maps) clustering to 50 nodes were performed with 37 functionally and phenotypically important immune markers. The Mann-Whitney U test identified significantly different cluster frequencies. Results: Correspondence analysis comparing global differences in cluster frequencies showed segregation of SLE subjects away from healthy controls. Multiple significant differences were identified (p &lt; 0.05). Notably, a memory CD4 + CD152 + PD1 + T cell subset (CD4 + CD152 + PD1 + CD45RO + CD25 - FoxP3 - ) was enriched in SLE (median: 2.17%, interquartile range: 1.66 to 7.74% of CD45+ PBMCs) versus control (1.34%, 1.06 - 1.58%; p = 0.00267). Expression of these known checkpoint inhibitors (PD1, CD152) could be important for SLE immunopathogenesis. Secondly, the innate lymphoid cell 2 (ILC2) subset (Lin - CD7 + CD25 + CD127 + GATA3 + ) was markedly depressed in SLE (0.11%, 0.1 - 0.255%) versus control (0.41%, 0.25 - 0.55%; p = 0.0293). ILC2s protect epithelial integrity; a reduction suggests impaired protective roles in SLE. Supervised cell frequencies from bivariate analysis correlate strongly with unsupervised cell frequencies, validating these results (Pearson’s correlation coefficient r = 0.9926, p &lt; 0.001 (CD4 + CD152 + PD1 + CD45RO + CD25 - FoxP3 - ); r = 0.8863, p &lt; 0.05 (ILC2)). Conclusion: With a multi-parametric, unbiased approach comparing SLE subjects to a large database of age-matched healthy controls, we identified two immune subsets of potential immunopathogenic importance. With this information, the CyTOF panel can be redesigned to probe more specifically into the SLE immunome, facilitating disease-specific interrogation. References: [1]Tsokos,G.C. (2011). Systemic lupus erythematosus. N Engl J Med 365(22), 2110-2121. [2]Bombardier, C., Gladman, D.D., Urowitz, M.B., Caron, D., Chang, C.H. (1992). Derivation of the SLEDAI. A disease activity index for lupus patients. The Committee on Prognosis Studies in SLE. Arthritis Rheum 35(6), 630-640. Disclosure of Interests: : None declared