The Imbalance Of Th17 And Treg In Patients With Chronic Obstructive Pulmonary Disease

BackgroundRecently, regulatory T cells (Tregs) and Th17 cells have been identified as two distinct CD4+T cell subsets from Thl and Th2 cells. Tregs express CD4 and CD25 on the cell surfaces, and they are identified by the nuclear expression of the characteristic transcription factor forkhead box P3 (FoxP3), while Th17 cells express retinoic acid-related orphan receptor C2 (RORC2). Tregs can limit the strength of the immune response of inflammatory cells by contact-dependent suppression or releasing anti-inflammatory cytokine interleukin-10(IL-10) and transforming growth factorβ(TGF-β), and have been shown to play an essential role in the induction and maintenance of peripheral tolerance, while Th17 cells possess very strong inflammatory properties by secretion of proinfammatory cytokines IL-17, IL-22, IL-23 and et al, and have been shown to play an critical role in a number of inflammatory diseases. So the imbalance of Th17 cells and Tregs(Th17/Treg imbalance) is supposed to play a pathogenic role in many inflammatory and autoimmune diseases, and this has been confirmed in lupus nephritis psoriasis, rheumatoid arthritis, idiopathic dilated cardiomyopathy, nasal polyposis, and et al. As a definite inflammatory disease, COPD may also be involved in the pathogenesis of this imbalance.ObjectiveThe objective of this study was to evaluate whether the Th17/Treg balance was broken in patients with COPD in both peripheral blood and local airways as well as to explore its significance in the pathogenesis of COPD.MethodsThe present study involved 21 patients with COPD,21 healthy smokers with normal lung function(HS)and 21 healthy non-smokers(HNS). In the peripheral blood, flow cytometry analysis was used to detect Th17 and Treg frequencies, however, in the sputum, there were not enough cells for flow cytometry analysis, and instead, we used real-time PCR to detect their characteristic transcription regulators, RORC2 and Foxp3 to analyze Th17 and Treg expression level. The concentrations of Th17 and Treg associated cytokines(IL-17, IL-10, TGF-β, IL-6) were detected in both serum and sputum with enzyme-linked immunoadsordent assay(ELISA).Results1. In the sputum from COPD patients, Th17/Treg was imbalanced at the characteristic transcription regulator level as well as cytokine level The level of RORC2 in sputum cells from COPD patients was higher than those from both HS group and HNS group, and the RORC2 mRNA was also higher in HS group than that of HNS group. However, up-regulation of Foxp3 mRNA was seen only in HS group. Sputum IL-17 was also upregulated while IL-10 failed.2. In the peripheral blood from COPD patients, Th17/Treg was also imbalanced at the characteristic transcription regulator levelIn the peripheral blood, Th17 cell frequencies and Treg cell frequencies were both up-regulated COPD patients. The level of RORC2 in PBMC from COPD patients, RORC2 mRNA and Foxp3 mRNA were unregulated in COPD group, and the ratio of RORC2 to Foxp3 was also higher than those in HS group and HNS group. Plasma IL-17 showed an increasing tendency (P=0.125) when compared with healthy non-smokers group, while a higher IL-10 concentration was seen.3. In COPD patients, higher levels of TGF-βand IL-6 were seen in both sputum and plasma when compared with those from HNS group4. Significant correlations(1) In smokers, the level of RORC2 insputum cells was positively correlated with smoking frequency.(2) The level of RORC2 in sputum cells was positively correlated with sputum TGF-β.(3) The level of sputum IL-17 positively correlated with that of sputum IL-6. (4) Both the level of RORC2 in sputum cells and sputum IL-17 were negatively correlated with FEV1 (pred%) and FEV1/FVC (%) separately.ConclusionOur study explored Thl7/Treg balance status in both airways and peripheral blood in COPD patients. In the local airways, Thl7/Treg was imbalanced, and inhibition by Treg was not sufficient, thus RORC2 activities and IL-17 was upregulated, which might play pathogenic roles in promoting airway inflammation, mucus hypersecretion as well as airway remodeling, and we found a negative correlation between IL-17and FEV1pred% or FEV1/FVC. in the peripheral blood, there was a relatively balanced status in Thl7/Treg cell frequencies, however, Thl7/Treg was imbalanced at the characteristic transcription regulator level, and this imblance might play a role in systemic damage. TGF-βand IL-6 were important points in regulating Th17/Treg balance status, however, the exact mechanism needed to be explored furtherly.