CHARACTERIZATION OF CCR8+ REGULATORY T CELLS IN RHEUMATOID ARTHRITIS

San Luis

Encuentro; LXXI Reunión Anual de la Sociedad Argentina de Inmunología (SAI); 2023

Sociedad Argentina de Inmunología

Rheumatoid Arthritis (RA) is a chronic autoimmune inflammatory disease characterized by joint destruction. In RA, immunoregulatory mechanisms mediated by Foxp3+ regulatory T cells may play fundamental roles but are poorly explored. The Treg compartment is heterogeneous, comprising several specialized subpopulations. Among them, CCR8+ Treg cells show enhanced suppression capacity and tissue repair functions that endows them with a detrimental role in cancer. The role of specialized Treg subsets in RA is unknown. We aimed study the phenotypic and functional characteristics of CCR8+ Treg cells in RA patients determining their protective or pathogenic role.We studied 53 patients diagnosed with RA according to ACR/EULAR 2010 classification criteria at the Hospital Nacional de Clínicas de Córdoba (24 untreated, 17 with synthetic DMARDs, 12 with biological DMARDs). Thirty healthy individuals age- and sex- matched were recruited as controls (HD). RA activity was assessed by the DAS28 index. Frequencies of Treg cells (CD3+CD4+CD25+FoxP3+) and CCR8+ Treg cells was measured by flow cytometry in cryopreserved mononuclear cells isolated from peripheral blood and synovial fluid (SF). Phenotypic characterization of CCR8+ Treg cells included the expression of regulatory molecules (CTLA-4, TIGIT, ICOS, CD39, and CD73) and tissue repair profile (GATA-3). Serum levels of CCL1, the CCR8 ligand, were measured by ELISA.We found that Treg cell frequency was slightly but significantly higher in the PBMC from patients versus controls (RA 4,41 ±1,81 vs HD 3,72 ± 1,30; p 0.046), while the frequency of the CCR8+ subset was similar between the two groups (RA 6.94 ± 3.77 vs HD 7.14 ± 2.99). Phenotypic characterization showed similar expression of CTLA-4, TIGIT, ICOS, CD39, CD73, and GATA-3 between CCR8+ Treg cells of RA and HD. Also serum levels of CCL1 were similar in RA and HD, and showed no correlation with the frequency of peripheral CCR8+ Treg cells. An initial functional evaluation determined lack of correlation between the percentages of Treg or CCR8+ Treg cells and the expression of IL-2, TNF, CD107, and CD57 in memory CD4+ and CD8+ T cells in RA and HD. Accordingly, percentages of Treg and CCR8+ Treg cells in RA showed no correlation with DAS28. Of note, CCR8+ Treg cells appeared to be increased in SF, where their frequency ranged between 18.5 and 39.4, (n=4). Altogether, we showed that, despite exhibiting increased peripheral Treg cells, RA patients present a conserved CCR8+ Treg cell frequency. No correlations were found between Treg cells and CCR8+ Treg cells frequencies and production of immune effector mediators or overall disease scores. The higher occurrence of CCR8+ Treg cells in LS suggests a likely preferential migration and enrichment in tissues. A deeper characterization of the CCR8+ Treg cell population in RA patients, including functional and transcriptomic evaluation, would allow us to better delineate the possible function of this subset in RA