Background Exhausted CD4⁺ T cells are recognised by low proliferation, increased cell death and high expression the inhibitory co-receptor programmed cell death-1 (PD-1). CD4⁺ T cells in patients with rheumatoid arthritis (RA) have recently been reported to show signs of exhaustion.¹ Exhaustion of CD4⁺ in experimental infection was associated with expression of interferon (IFN) response genes,² referred to as the IFN signature. In human, the IFN signature has been suggested to predict rheumatoid arthritis (RA).³

We investigated if CD4⁺ T cells with an exhausted phenotype and IFN signature are accumulating in peripheral blood of RA patients. We study a connexion between CD4⁺ T cell exhaustion and survivin expression in RA.

Materials and methods IFN response genes, PD-1 and survivin expression were analysed in peripheral blood of RA patients and healthy women with different smoking status using flow cytometry and qPCR. The role of survivin in the formation of exhausted CD4⁺ T cells was studied in the collagen-induced arthritis model, where mice where treated with nicotine or vaccinated with survivin peptides.

Results High frequency of exhausted PD-1⁺CD4⁺ cells was found in smoking RA patients. The numbers of PD1⁺CD4⁺ cells correlated inversely with the PD-1 expression by cytotoxic CD8⁺CD107⁺ cells (r=−0.62, p=0.01). Additionally, the frequency of PD-1⁺CD4⁺ cells increased with reduction of the CD4⁺ population (r=−0.71, p=0.002). The IFN signature was found exclusively among smoking RA patients. The patients with the IFN signature all had CD4⁺ cells with low survivin production. Sorted Th17 cells from RA patients with high serum levels of survivin had higher transcription of exhaustion related genes compared to healthy controls. CD4⁺ cells with high survivin expression were negative for PD-1. In mice, the survivin^hiPD-1^- population of CD4⁺ cells was reduced in nicotine-treated mice (p=0.03) and in response to activation of survivin targeting cells through vaccination (p=0.009).

Conclusions We show that smoking associates with exhaustion of CD4⁺ T cells in RA. Smoking increases the frequency of PD-1⁺CD4⁺ cells with the IFN signature by activating survivin targeting mechanisms.

References

1. Frenz, T, et al, CD4+ T cells in patients with chronic inflammatory rheumatic disorders show distinct levels of exhaustion. Journal of Allergy and Clinical Immunology, 2016;138(2):p.586–589.e10.

2. Crawford, A, et al, Molecular and Transcriptional Basis of CD4+ T Cell Dysfunction during Chronic Infection. Immunity2014;40(2):p.289–302.

3. Lübbers, J, et al, The type i IFN signature as a biomarker of preclinical rheumatoid arthritis. Annals of the Rheumatic Diseases2013;72(5):p.776–780.