gms | German Medical Science

Introduction: Rheumatoid Arthritis (RA) is an autoimmune disease characterized by chronic inflammation primarily affecting the synovial membrane of the small joints. Autoreactive T cells play a decisive role and contribute to pro-inflammatory milieu in RA. We could show previously that CD4+CD8+ double-positive (DP) T cells conduce to increased disease activity and joint erosions in RA patients [1]. Hence, we are interested in functional and phenotypic characterization of DP T cells.

Methods: Peripheral blood mononuclear cells (PBMCs) from RA patients and healthy donors (HD) were isolated by density gradient centrifugation. Surface and intracellular expression of T cell markers (CD3, CD4, CD8, CD8 CD27, and CCR7) and transcriptions factors (T-Bet, Eomes, Runx3, and ThPOK) were analyzed. The proliferation rate of sorted CD4+ single positive (SP) and DP T cells was measured using CFSE proliferation assay after five days stimulation. All cells were analyzed by flow cytometry.

Results: First results show that an increased percentage of RA DP T cells (n=11) exhibit a phenotype of memory (CD27+) T cells (70.3%) and 20.1% of DP T cells are terminally differentiated (CCR7-CD27-). Naive DP (CCR7+CD27+) cells are less represented (<10%). Moreover, proliferative potential of DP T cells (n=2; 91%) was comparable to CD4+SP (>90,5%) T cells. Furthermore, comparison of the transcriptions factor expression levels revealed higher expression levels of T-bet (n=6; MFI=660.7) and Eomes (n=3; MFI=154.4) in DP, especially of CD4highCD8low T cells in comparison to CD4+SP (MFI T-bet=354.2; MFI Eomes= 98.4). Whereas CD4+SP and DP showed similar expression levels of Runx3 (n=6; CD4+SP MFI=478; DP MFI=473.5) and ThPOK (n=4; CD4+SP MFI=149.7; DP MFI=139.4). In general, HD T cells showed a higher percentage and expression level of all transcription factors in comparison to RA T cells.

Conclusion: In summary, expression of both T cell differentiation markers CD27 and CCR7 and transcription factors revealed an effector-memory T cell phenotype with a high proliferative potential that may contribute to RA inflammation because of their Th1 specific phenotype.