Background/Purpose:

The presence of ACPA in RA indicates that an immune response directed toward citrullinated synovial antigens participates in disease development or persistence. Research from our group have identified T cell targets derived from the auto-antigens aggrecan, vimentin, fibrinogen, alpha-enolase, and cartilage intermediate layer protein (CILP). In this study, we visualized peripheral antigen-specific CD4+ T cells using a multiplexed flow-cytometry based HLA class II tetramer assay in a cross-sectional cohort of 80 RA and 30 matched healthy control subjects to understand their relevance to RA disease progression and response to therapy.

Methods:

All subjects were DRB1*04:01. RA subjects were CCP positive and represented a range of characteristics including time from diagnosis, disease activity and treatment at the time of blood draw. Antigen-specific T cells were visualized by directly staining peripheral blood mononuclear cells (PBMC) with multiple tetramers corresponding to different antigens. Frequencies and phenotypic features of antigen-specific CD4+ T cells were assessed for correlation with clinical characteristics.

Results:

Ex-vivo analysis of PBMC revealed an increase in synovial targeted CD4 T cells when compared to matched healthy DRB1*04:01 subjects. When analyzed by individual antigen CD4 T cells, aggrecan, vimentin and fibrinogen were increased in RA, and by contrast cartilage-intermediate-layer-protein (CILP) and enolase specific T cells were reduced in comparison to healthy subjects, suggesting that the characteristics of the CD4+ T cells response to synovial epitopes may be unique to antigen specificity.

Within this patient cohort we found a lower frequency of synovial specific T cells in individuals on TNF therapies sampled within 5 years of diagnosis. These differences were most pronounced in the CD4 T cells specific for aggrecan, vimentin and fibrinogen, and showed alterations in chemokine receptor and activation marker expression in the treated group.

Ongoing studies will determine if frequency, phenotype and specificity of synovial specific CD4 T cells correlate directly with disease duration, therapeutic duration, and clinical diagnostic values such as level of RF, CCP, CRP, and disease severity.

Conclusion:

We have shown that a multiplexed tetramer assay can define the breadth and character of the T cell response to synovial antigens. Characterizing a relatively large cohort of subjects, we demonstrate differences in the phenotype and frequency of the T cells that respond to a diverse set of synovial antigens thought to be important targets in RA. In particular, we show that synovial specific T cell frequency is influenced by therapeutic interventions. Better understanding the interplay of antigen specificities and phenotypes in RA is vital to understanding disease pathogenesis, response to therapy and ultimately developing antigen specific therapies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cross-sectional-analysis-of-citrullinated-synovial-antigen-specific-cd4-t-cells-in-an-ra-cohort-demonstrates-antigen-based-differences-in-t-cell-frequency-phenotype-and-the-influence-of-immunotherap/