P19 Frequencies of IL-17+CD8+ T-cells and tissue resident memory T-cells in early inflammatory arthritis
Authors: Hughes Catherine D , Steel Kathryn J. A , Ryan Sarah , Lahnunlimi Sylvine , Menon Bina , Taams Leonie S , Kirkham Bruce W 
Published: April 2020

Abstract

Background
Early inflammatory arthritis (EIA) is classically described as arthritis of ≤ 12 months duration. EIA can be sub-divided into psoriatic arthritis (PsA), other spondyloarthritides (SpA), rheumatoid arthritis (RA) or reactive arthritis (ReA). EIA is often difficult to classify. IL-17+CD8+ T-cells have previously been identified within the joints of patients with PsA. Many of these cells have properties of tissue resident memory (TRM) T-cells, a recently defined subset of CD8+ T cells which remain resident within tissues ready to respond rapidly. We sought to identify the presence and frequency of Tc17 and/ or TRM cells within the joints of patients with EIA to facilitate correct diagnosis and management.

Methods
27 EIA patient samples were collected from patients in the Rheumatology clinic setting. Consent was obtained using established ethics. Samples underwent synovial fluid mononuclear cell (SFMC) isolation and cryopreservation. After thawing, 2 million cells from each sample were stimulated for 3 hours with PMA, Ionomycin and Golgistop. Samples were stained for CD-3, CD-14, CD-4, CD-8 and cytokine expression (IL-17, IFN- γ and TNF-α). A further 2 million cells from 21 of these samples were stained using an extracellular stain for the presence of TRM cells (CD69+CD103+ CD8+ T cells). Samples were all acquired on BD Canto. Analysis was completed using FlowJo and PRISM.

Results
Patients were classified into disease groups based on clinical features and laboratory results, blinded to the SF results. Seronegative RA was subdivided based on disease pattern into RA like or oligo-arthritis like. Patient numbers per group: seropositive RA = 5, seronegative RA (RA-like) =4, seronegative RA (oligo-like) =8, PsA=4, SpA=6. The frequency of Tc17 cells was significantly increased in SF of patients with PsA compared to all other groups (ordinary one-way ANOVA p &lt; 0.0001). Specific comparisons were seropositive RA vs PsA (p = 0.003), seronegative RA vs PsA (RA like p = 0.0002, oligo IA p &lt; 0.0001) and PsA vs SpA (p = 0.0013). The frequency of TRM cells was also significantly increased in PsA compared to all other groups (ordinary one-way ANOVA p = 0.0013), and specific groups: seropositive RA and PsA (p = 0.0031), seronegative RA and PsA (RA like p = 0.0086, oligo IA p = 0.0039) and PsA and SpA P = 0.0009. In contrast, Th17 cells and IFN-γ+ CD8+ T-cells (Tc1 cells) were found in all SF with no significant difference between sub-groups.

Conclusion
This preliminary study of 27 patients with EIA shows that the frequency of Tc17 and CD69+CD103+CD8+ TRMcells are increased in the SF of patients with early PsA compared to other patient groups. Our data also show that TRM cells are present at detectable frequencies in the joints of most patients with EIA. Further work is required to establish if these cells could function as a clinical biomarker to aid diagnosis.

Disclosures
C.D. Hughes None. K.J.A. Steel None. S. Ryan None. S. Lahnunlimi None. B. Menon None. L.S. Taams None. B.W. Kirkham Consultancies; BK has worked as a consultant for Eli Lilly, Gilead, Jannsen and Novartis. Grants/research support; BK has received research support from Eli Lilly and Novartis.