Background/Purpose

CCR6 has been associated with rheumatoid arthritis (RA) in genome-wide association studies. CCR6 expression characterises Th17 cells recruited to inflamed joints of RA patients.  The purpose of this study was to characterize gene transcription in the peripheral lymphocytes in RA patients.

Methods

CCR6⁺CD4⁺ cells were isolated from peripheral blood leukocytes of 14 RA patients and 6 healthy controls by magnetic beads. The isolated cells consisted of 85% CCR6⁺CXCR3^–cells and had a viability of 94%. Cells were stimulated with PMA/ionomycine for 4h, supernatants were collected for cytokine analysis and cell pellets were used for gene expression analysis using nCounter Analysis System (NanoString Technologies).

Results

Transcription analysis showed that 140 genes had significant (p<0.05) ≥1.5-folds difference between CCR6⁺CD4⁺ cells of RA patients and healthy controls. As expected, RA patients CCR6⁺CD4⁺ cells were also CCR5^–CXCR3^–. Despite the intense immunosuppression with methotrexate and TNF-inhibitors, RA lymphocytes had had higher transcription of Th17 cytokines (IL17F, IL17A, IL22). Also Th17 (Rorc) and Th1 (Tbx21 and Egr-2) differentiation genes were enhanced, while other genes regulating IL-22 production (Ahr and NFAT1) were repressed. Genes controlling the formation of Th17(Beta) and Th17(23) subtypes were increased, and inhibitors of this formation were repressed. Transcription of IL23 receptor complex genes (IL23R, Jak2, e.g.) was up-regulated and production of IL23A and CCL20 was increased.

RA lymphocytes had a significant increase in the follicular T helper cell profile, characterized by the surface markers CXCR5 and ICOS, and the master transcription regulator Bcl-6. CXCR5 expression was combined with higher CCR6 and lower CXCR3. The enrichment of CXCR5⁺CCR6⁺CXCR3^– phenotype was supported by expression of cytokine IL21. The cytokines activating the gp130-receptor family (IL31, IL35 and Lif), were increased. Interestingly, gp130-associated signalling in the CCR6+CD4+ cells was dampened by low IL27R, low STAT signal (reduced STAT1, STAT3, STAT4) and low transcriptional regulator AhR, suggesting that the gp130 activation occurs on a cell populations different from the studied, e.g.B-cells.

Conclusion

This study demonstrates that CCR6⁺CD4⁺ T cells of RA patients have features of proliferative, proinflammatory and IL17 producing cells controlled through TGFb and IL23 mediated signalling. CCR6⁺CD4⁺ T cells are a source of CXCR5⁺ Tfh cells efficient producers of IL21 cytokine presumably stimulating autoantibody production in RA patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/ccr6cd4-cells-are-counterparts-of-follicular-t-cells-supporting-autoantibody-production-in-rheumatoid-arthritis/