Background:CD4+ T cells with cytotoxic functions (CD4+ CTL) have gained attention in recent years. Accumulating evidence supports their importance in defense against human viral infections such as CMV1, EBV2, dengue3, HIV4, 5 and SARS-CoV-26. Moreover, expansion of so called CD28null cytotoxic CD4+ T cells have been reported in the blood of patients with rheumatic diseases such as rheumatoid arthritis (RA)7, myositis8 and vasculitis9 as well as in cardiovascular diseases10.Objectives:Here, we aimed to investigate the presence and clonal expansion of CD4+ CTL in the peripheral blood (PB) and synovial fluid (SF) of RA patients using single cell technologies.Methods:We assessed the expression of cytotoxic effector molecules and transcription factors in CD4+ T cells in synovial fluid (n=21) and paired peripheral blood (n=16) from ACPA- and APCA+ RA patients by multi-parameter flow cytometry. We performed single cell sequencing, in combination with 5´ TCRab sequencing, on purified CD4+ T cells from the peripheral blood (PB) and synovial fluid (SF) of ACPA+ RA patients (n=7).Results:Flow cytometry experiments show that Granzyme-B+ Perforin-1+ CD4+ CTL are significantly increased in the SF of ACPA+ RA patients as compared to ACPA- RA patients (p=0.0072). The presence of CD4+ CTL could be confirmed by single cell sequencing in SF of each ACPA+ RA patient tested (n=7). Moreover, we found that the adhesion G-protein coupled receptor GPR56 is selectively expressed on the recently described peripheral helper (TPH) T-cell subset11 and associates with the expression of tissue resident memory markers LAG-3, CXCR6 and CD69. In blood, we confirmed a previous report12 showing that GPR56 delineates cytotoxic CD4+ T cells. Finally, expanded TCR clones expressing cytotoxic effector molecules were identified in synovial fluid of ACPA+ RA patients and, for some patients, in their corresponding peripheral blood.Conclusion:We identified GPR56 as a marker of TPH cells in SF of ACPA+ RA patients that associates with tissue residency receptors. The combination of single cell sequencing and multi-parameter flow cytometry highlights the importance of CD4+ CTL in ACPA+ RA and suggests a potential therapeutic target (Figure 1).References:[1]Casazza J. P. et al., J Exp Med2006,203 (13), 2865-77.[2]Landais E. et al., Blood2004,103 (4), 1408-16.[3]Kurane I. et al. J Exp Med1989,170 (3), 763-75.[4]Appay V. et al. J Immunol2002,168 (11), 5954-8.[5]Juno J. A. et al. Front Immunol2017,8, 19.[6]Meckiff B. J. et al. Cell2020,183 (5), 1340-1353 e16.[7]Schmidt D. et al. J Clin Invest1996,97 (9), 2027-37.[8]Fasth A. E. et al. J Immunol2009,183 (7), 4792-9.[9]Moosig F. et al. Clin Exp Immunol1998,114 (1), 113-8.[10]Sato K. et al. J Exp Med2006,203 (1), 239-50.[11]Rao D. A., et al. Nature2017,542 (7639), 110-114.[12]Peng Y. M. et al. J Leukoc Biol2011,90 (4), 735-40.Acknowledgements:We thank the patients who donated samples and the medical staff at the Rheumatology Clinic of Karolinska University Hospital. Julia Boström, Gloria Rostvall, and Susana Hernandez Machado are acknowledged for organizing the sampling, storage, and administration of biomaterial. This study is supported by grants from Dr. Margaretha Nilssons, the Nanna Svartz, the Ulla and Gustaf af Ugglas foundations and the Swedish association against rheumatism.Disclosure of Interests:Alexandra Argyriou: None declared, Marc H Wadsworth II Employee of: Pfizer, Inc, Cambridge, MA 02139, United States, Adrian Lendvai: None declared, Stephen Christensen Employee of: Pfizer, Inc, Cambridge, MA 02139, United States, Aase Hensvold: None declared, Christina Gerstner: None declared, Kellie Kravarik Employee of: Pfizer, Inc, Cambridge, MA 02139, United States, Aaron Winkler Employee of: Pfizer, Inc, Cambridge, MA 02139, United States, Vivianne Malmström: None declared, Karine Chemin: None declared
Landscape of Infiltrating T Cells in Liver Cancer Revealed by Single-Cell Sequencing
