Background/Purpose: Biologics have transformed the management of axial spondyloarthritis (axSpA). Currently, it is challenging to identify patients who would benefit from early biologics, resulting in trial-and-error use of NSAIDs followed by a response evaluation over months before initiating biologics. This study aimed to characterize patients requiring early biologics through single-cell RNA sequencing (scRNA-seq) analysis of peripheral blood mononuclear cells (PBMCs) obtained from newly diagnosed axSpA patients.

Methods: PBMCs were collected at baseline from axSpA patients newly diagnosed. Patients initiating biologics within six months were categorized as early biologics users, while those who did not were categorized as non-early biologics users. Single-cell RNA sequencing data were processed using Cell Ranger, and quality control was performed using Seurat. Differences in cell proportions were analyzed with scProportionTest, and differentially expressed genes (DEGs) were identified using the Wilcoxon Rank Sum test. Pathway enrichment analyses were conducted using KEGG and GO terms.

Results: Nineteen patients with axSpA were enrolled, of whom seven were categorized as early biologics users and twelve as non-early biologics users. A total of 157,029 single cells passed quality control and were included in subsequent analyses. Differential cell proportion analysis revealed marked differences between early and non-early biologics users. Specifically, early biologics users exhibited a significant increase in monocyte proportions, along with a decrease in NK and CD8+ T cells, suggesting an altered balance in both innate and adaptive immunity. Monocytes had the highest number of differentially expressed genes (DEGs), highlighting the potential importance of monocytes in determining early treatment responses (Figure 1).Enrichment analyses of monocyte-specific DEGs indicated significant activation of pathways closely linked to the pathogenesis of axSpA, including NF-κB signaling, the Toll-like receptor signaling pathway, the response to tumor necrosis factor, and MAPK signaling (Figure 2). In CD8+ T cells, DEGs were enriched in the HIF signaling pathway in the KEGG gene set. These findings are consistent with previous reports emphasizing the necessity of increased glycolysis in supporting CD8+ T cell activation and differentiation. Similarly, NK cells in early biologics users displayed DEGs such as FPR1, XCL2, CYBB, CD14, FOS, LYZ, S100A9, AIF1, and S100A8, which are enriched in inflammatory response pathways. NK cells have been implicated in several immune-mediated diseases, and these results suggest that their dysregulation may contribute to the early disease process in axSpA.

Conclusion: These data indicate that early biologics users exhibit a distinct immunological profile characterized by enhanced monocyte-driven inflammation and concurrent alterations in CD8+ T cell and NK cell populations. These findings underscore the critical role of innate immunity, particularly through monocyte-mediated pathways, in identifying patients who may benefit from early biologics therapy, offering a basis for personalized therapeutic strategies.

Figure 1. Single-cell proportion test results. To compare cell type proportions between early and non-early users, a single-cell proportion test was performed using the R package scProportionTest.

Figure 2. Results of the enrichment analysis. Enrichment analyses using (a) GO Biological Process and (b) KEGG gene sets.

« Back to ACR Convergence 2025

ACR Meeting Abstracts - https://acrabstracts.org/abstract/single-cell-rna-sequencing-highlights-the-role-of-innate-immunity-in-identifying-candidates-for-early-biologics-treatment-in-axial-spondyloarthritis/