Graduate Korea Advanced Institute of Science and Technology Daejeon, United States
Disclosure(s):
Woogil Song, PharmD: No financial relationships to disclose
Introduction/Rationale: Pathologic programs of human Th17 cells remain incompletely defined. Profiling memory CD4⁺ T cells from healthy controls (HC) and patients with psoriasis (PS), rheumatoid arthritis (RA), and ankylosing spondylitis (AS), we identified a PDE4D hi Th17 subset (P_Th17) whose features suggested arthritis-predominant biology and potential antigenic convergence.
Methods: We performed 5′ scRNA-seq with paired scTCR-seq on magnetic bead–sorted memory CD4⁺ T cells from 64 donors (HC, PS, RA, AS; n=16 each). Condition-enriched states were mapped by unsupervised clustering, MiloR neighborhood testing, and cNMF program analysis. PDE4D isoforms were quantified with our pipeline. Synovial fluid/tissue (including spatial) datasets were analyzed to localize disease signals. Gain-of-function was tested by overexpressing short PDE4D isoforms (PDE4D1/2) in human memory CD4⁺ T cells.
Results: P_Th17 were increased in disease, with an AP-1–high subset specifically elevated in RA/AS. In patient synovial fluid, polyfunctional Th17 also exhibited high PDE4D. Isoform-resolved analysis showed selective upregulation of short isoforms (PDE4D1/2) within P_Th17; not all isoforms rose. The pathologic Th17 NMF program correlated strongly with short-isoform burden. TCR repertoire analysis revealed focused clonal expansions and shared CDR3β motifs within P_Th17, indicating antigen-driven selection consistent with tissue specificity. Upon anti-CD3/CD28 stimulation, Th17 cells with high P_Th17 features increased at the RNA level. Overexpression of PDE4D1/2 in human memory CD4 T cells enhanced activation and polyfunctional cytokine potential, supporting a short-isoform–dependent mechanism.
Conclusion: Arthritis is marked by a PDE4Dhi, AP-1–linked Th17 state with short-isoform dependency that aligns with polyfunctional Th17 signatures in inflamed synovium. Isoform-specific PDE4D regulation and arthritis-specific P_Th17 markers emerge as actionable axes for mechanistic dissection and therapeutic targeting.
