Characteristics of monocyte subpopulations in peripheral blood of the patients with chronic obstructive pulmonary disease

Abstract

Rationale. As the precursors of macrophages, monocytes play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Traditionally, classical (CD14++CD16–), intermediate (CD14++CD16+) and non-classical (CD14+CD16++) subpopulations of monocytes are distinguished, which differ in their functional characteristics.Aim: To study the relative amount of circulating subpopulations of monocytes in patients with COPD and to identify their possible relationship with pulmonary function and humoral inflammatory markers.Methodology and Research Methods. The study enrolled 47 patients with COPD, predominantly GOLD II-III, and 25 individuals without bronchial obstruction (control group). Monocyte subpopulations were determined by flow cytometry. Plasma cytokine concentrations were measured using a multiplex assay on a flow cytometer. Pulmonary function was assessed by spirometry.Results. A reduced number of non-classical monocytes was observed in COPD patients as compared to the control group (10.5 (6.7–15.1)% vs. 14.4 (8.3–18.4)%, p = 0.04). Higher content of classical monocytes was associated with a more pronounced decrease in bronchial patency (FEV1 ρ = –0.37, p = 0.007), while intermediate monocytes were characterized by a direct relationship with FEV1 (ρ = 0.42, p = 0.003). The number of non-classical monocytes in the main group had an inverse correlation with cytokine concentrations (IL-4 ρ = –0.30, p = 0.04; IL-2 ρ = –0.36, p = 0.01; IL-1β ρ = –0.35, p = 0.02; TNF-α ρ = –0.47, p < 0.001; IL-17A ρ = –0.34, p = 0.02; IL-6 ρ = –0.32, p = 0.03; IL-10 ρ = –0.34, p = 0.02; IFN-γ ρ = – 0.35, p = 0.01; IL-12p70 ρ = –0.30, p = 0.04; IL-8 ρ = –0.40, p = 0.004).Conclusion. The obtained results indicate a deficiency of non-classical monocytes in COPD patients, which may contribute to systemic inflammatory response, while classical forms of monocytes may be involved in the formation of bronchial obstruction.