Background/Purpose: Resident memory T cells (TRM) are site-specific memory T cells that take up long-term residence in peripheral tissues and aid in pathogen defense. Dysregulated TRM cells have also been implicated in autoimmune diseases by driving localized recurrent inflammation. As RA and JIA are characterized by recurrent joint inflammation, we asked whether TRM cells can be identified in human RA synovium.

Methods: Multicolored tyramide-based immunostaining was performed on formalin-fixed paraffin embedded synovium tissue obtained from RA patients. Tissues were stained with antibodies against CD3, CD8, CD4, CD45RO, CD69 and CD103 surface antigens. Nuclei were visualized with DAPI staining. Immunofluorescence was assessed by immunofluorescence microscopy using the Mantra quantitative pathology imaging and analysis platform. TRM cells were identified by their cell surface expression signature. To identify whether T cells in RA synovium shared a transcriptome signature with TRM cells, we utilized 10X Genomics droplet-based single cell RNA sequencing technology to evaluate gene expression of individual T cells. Leukocytes were harvested from disaggregated RA synovial tissue and memory T cells (CD3+CD45RO+) were enriched by FACS sorting prior to 10X sequencing. We utilized immune cell repertoire profiling that integrates a step into the 10X workflow for targeted amplification of full-length VDJ sequences with primers for the T cell receptor constant regions of both alpha and beta chains.

Results: Using Mantra multispectral immunofluorescence imaging, we visualized synovial cells bearing a signature consistent with TRM cells (CD3+CD45RO+CD69+CD103+) in RA synovium. Single-cell RNA sequencing data of memory T cells isolated from RA synovium revealed a subset of cells with a gene expression signature that is consistent with TRM cells. These CD8-expressing cells demonstrated a transcriptome consistent with immune cell activation and chemokine signaling and displayed a restricted TCR expression profile within the top 0.5% of predominant T cell clones.

Conclusion: We identified T cells with a cell surface expression profile consistent with TRM cells in human RA synovium, across multiple donors. Single-cell RNA sequencing showed that a subpopulation of memory T cells isolated from RA synovium have a transcriptomic signature that is consistent with TRM cells identified in other tissues. These cells are restricted in their TCR sequences and represent some of the most abundant T cell clones in RA synovium. They also express genes involved in immune cell activation and recruitment, suggesting an active role in inflammation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/resident-memory-t-cells-in-human-ra-synovium-display-restricted-tcr-clones/