Single cell transcriptome and surface protein expression analysis identify OX40 + GITR + pathogenic T helper 17 in ankylosing spondylitis.

OBJECTIVES: To demonstrate the immune landscape of blood and synovial cells in AS through both single cell transcriptome and surface protein expression analysis to unveil the molecular characteristics of pathogenic Th17 cells (pTh17) METHODS: 40 active AS, 20 stable AS, 40 active RA patients, and 20 healthy control were included in the study. Surface phenotype and intracellular staining after T cell receptor stimulation of peripheral blood mononuclear cells and synovial fluid mononuclear cells were assessed using flow cytometr. Single cell transcriptome of six patients with active AS were studied along with and cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq). We also assessed the outcome of targeting OX40 and GITR on the cell surface of Th17 cells in the curdlan-injected SKG mouse model using anti-GITRL and/or anti-OX40L.

RESULTS: We identified pTh17 cells as polyfunctional IL-17A and IFN-γ-producing memory CD4+ T cells, with clinically supporting evidence for their pathogenic roles at the inflammatory site of AS. Transcriptome and flow cytometric analysis found that the co-expression of TNFRSF4 (OX40) and TNFRSF18 (GITR, glucocorticoid-induced TNF receptor) is increased in pTh17 cells. In vivo suppression of ligand-receptor interactions via OX40 and GITR effectively suppressed clinical arthritis and decreased pTh17 cells in the curdlan-injected SKG mouse model.

CONCLUSIONS: Our results have implications for understanding pTh17 cells in AS and suggest potential therapeutic targets.