Background: Chronic obstructive pulmonary disease (COPD) is characterized by an enhanced and persistent innate and acquired immune response to tobacco smoking. Myeloid-derived suppressor cells (MDSCs) modulate T-cell responses by down-modulating the T cell receptor ζ chain (TCR ζ) through the catabolism of l-arginine. The effects of smoking on MDSCs and their potential participation in COPD immunopathogenesis have not been explored so far.
Methods: To investigate it, we compared the level of circulating Lineage-/HLA-DR-/CD33+/CD11b+ MDSCs, the serum concentration of arginase I (ARG I) and the expression of peripheral T-cell receptor ζ chain (TCR ζ) in never smokers, smokers with normal spirometry and COPD patients. Flow cytometry was used to quantify circulating MDSCs and TCR ζ expression. Serum ARG I levels were determined by ELISA.
Results: The main findings of this study were that: (1) current smoking upregulates and activates circulating MDSCs both in smoker controls and COPD patients; and, (2) at variance with the smokers with normal spirometry, in patients with COPD this effect persists after quitting smoking and is accompanied by a significant and specific down-regulation of the TCR ζ chain expression in circulating T lymphocytes.
Conclusion: Smoking modulates circulating MDSCs. Their regulation appears altered in patients with COPD.
Keywords: ARG I; Arginase I; COPD; Chronic inflammation; Chronic obstructive pulmonary disease; MDSCs; Myeloid cells; Myeloid derived suppressor cells; PBMCs; Peripheral blood mononuclear cells; T-cell receptor ζ chain; TCR ζ.
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