Th104 - Synovium CD4+HLADR+ T Effectors with Antigenic Reactivity That Sustain Inflammation and Resist Regulatory Control in Juvenile Idiopathic Arthritic Patients

Pavanish Kumar – Translational Immunology Institute – Singhealth/Duke-NUS Academic Medical Centre; Shi Huan Tay – Translational Immunology Institute – Singhealth/Duke-NUS Academic Medical Centre; Gerdien Mijnheer – Center for Translational Immunology – University Medical Center Utrecht; Joo Guan Yeo – Division of Medicine – KK Women’s and Children’s Hospital; Sharifah Nur Hazirah – Translational Immunology Institute – Singhealth/Duke-NUS Academic Medical Centre; Amanda Jin Mei Lim – Translational Immunology Institute – Singhealth/Duke-NUS Academic Medical Centre; Camillus Chua – Translational Immunology Institute – Singhealth/Duke-NUS Academic Medical Centre; Phyllis Chen – Translational Immunology Institute – Singhealth/Duke-NUS Academic Medical Centre; Alessandro Consolaro – Second Paediatric Division – University of Genoa and G Gaslini Institute; Marco Gattorno – Second Paediatric Division – University of Genoa and G Gaslini Institute; Femke van Wijk – Center for Translational Immunology – University Medical Center Utrecht; Alberto Martini – Second Paediatric Division – University of Genoa and G Gaslini Institute; Thaschawee Arkachaisri – Division of Medicine – KK Women’s and Children’s Hospital; Salvatore Albani – Translational Immunology Institute – Singhealth/Duke-NUS Academic Medical Centre

Abstract Text: Systemic CD4+HLADR+ effectors and Tregs from arthritic patients have been shown to exhibit immunological and TCR profiles resembling synovium counterparts. Notably, circulatory CD4+HLADR+ effectors were elevated in arthritic individuals non-responsive to TNFi treatments. Why synovium CD4+HLADR+ effectors continue to sustain inflammation despite presence of Tregs and its relationship with analogous CD4+HLADR+ Tregs remains unknown. We employed CyToF to interrogate the CD4 memory landscape of JIA patients, and revealed the elevated presence of CD4+HLADR+ effectors expressing TNFa, IFNg and IL-21 within the synovium. CD4+HLADR+ effectors and Tregs positively correlated strongly across the circulatory and synovium compartments. To unravel their relationships and understand their functional properties, we sorted CD4+HLADR+/- subsets and performed deep RNAsequencing. CD4+HLADR+ effectors and Tregs displayed strong transcriptomic convergence, higher TCR clonatype sharing and were enriched for 7 key pathways, including MHC-II and IFNg signalling. While synovium CD4+HLADR+ Tregs presented stable FoxP3 promoter methylation profiles and were competent suppressors, CD4+HLADR+ effectors were able to resist their regulatory control. CD4+HLADR+ Tregs were unstable in the presence of Th-1 polarising and mitotic conditions, decreasing FoxP3 levels, as compared with CD4+HLADR- Tregs. Furthermore, CD4+HLADR+ effectors responded to disease relevant antigens (HSP60) independent of APCs. In summary, this study has shown the pathogenic mechanisms through which CD4+HLADR+ effectors could contribute to persistent autoimmunity in JIA patients. Specific targeting of CD4+HLADR+ effectors in JIA may present as a potential therapeutic avenue.