Expansion of CD4+CD25+ helper T cells without regulatory function in smoking and COPD.

BACKGROUND: Regulatory T cells have been implicated in the pathogenesis of COPD by the increased expression of CD25 on helper T cells along with enhanced intracellular expression of FoxP3 and low/absent CD127 expression on the cell surface. METHOD: Regulatory T cells were investigated in BALF from nine COPD subjects and compared to fourteen smokers with normal lung function and nine never-smokers. RESULTS: In smokers with normal lung function, the expression of CD25+CD4+ was increased, whereas the proportions of FoxP3+ and CD127+ were unchanged compared to never-smokers. Among CD4+ cells expressing high levels of CD25, the proportion of FoxP3+ cells was decreased and the percentage of CD127+ was increased in smokers with normal lung function. CD4+CD25+ cells with low/absent CD127 expression were increased in smokers with normal lung function, but not in COPD, when compared to never smokers. CONCLUSION: The reduction of FoxP3 expression in BALF from smokers with normal lung function indicates that the increase in CD25 expression is not associated with the expansion of regulatory T cells. Instead, the high CD127 and low FoxP3 expressions implicate a predominantly non-regulatory CD25+ helper T-cell population in smokers and stable COPD. Therefore, we suggest a smoking-induced expansion of predominantly activated airway helper T cells that seem to persist after COPD development.

Cytotoxic T cells expressing the co-stimulatory receptor NKG2 D are increased in cigarette smoking and COPD.

BACKGROUND: A suggested role for T cells in COPD pathogenesis is based on associations between increased lung cytotoxic T lymphocyte (CD8+) numbers and airflow limitation. CD69 is an early T cell activation marker. Natural Killer cell group 2 D (NKG2D) receptors are co-stimulatory molecules induced on CD8+ T cells upon activation. The activating function of NKG2 D is triggered by binding to MHC class 1 chain-related (MIC) molecules A and B, expressed on surface of stressed epithelial cells. The aim of this study was to evaluate the expression of MIC A and B in the bronchial epithelium and NKG2 D and CD69 on BAL lymphocytes in subjects with COPD, compared to smokers with normal lung function and healthy never-smokers. METHODS: Bronchoscopy with airway lavages and endobronchial mucosal biopsy sampling was performed in 35 patients with COPD, 21 healthy never-smokers and 16 smokers with normal lung function. Biopsies were immunohistochemically stained and BAL lymphocyte subsets were determined using flow cytometry. RESULTS: Epithelial CD3+ lymphocytes in bronchial biopsies were increased in both smokers with normal lung function and in COPD patients, compared to never-smokers. Epithelial CD8+ lymphocyte numbers were higher in the COPD group compared to never-smoking controls. Among gated CD3+cells in BAL, the percentage of CD8+ NKG2D+ cells was enhanced in patients with COPD and smokers with normal lung function, compared to never-smokers. The percentage of CD8+ CD69+ cells and cell surface expression of CD69 were enhanced in patients with COPD and smokers with normal lung function, compared to never-smokers. No changes in the expression of MIC A or MIC B in the airway epithelium could be detected between the groups, whereas significantly decreased soluble MICB was detected in bronchial wash from smokers with normal lung function, compared to never-smokers. CONCLUSIONS: In COPD, we found increased numbers of cytotoxic T cells in both bronchial epithelium and airway lumen. Further, the proportions of CD69- and NKG2D-expressing cytotoxic T cells in BAL fluid were enhanced in both subjects with COPD and smokers with normal lung function and increased expression of CD69 was found on CD8+ cells, indicating the cigarette smoke exposure-induced expansion of activated cytotoxic T cells, which potentially can respond to stressed epithelial cells.

Influence of smoking cessation on airway T lymphocyte subsets in COPD.

The mechanisms behind airway inflammation in chronic obstructive pulmonary disease (COPD) are still not well understood. Here we investigated lymphocyte subtypes in bronchoalveolar lavage fluid, likely to be involved in the pathogenesis of COPD, as well as exploring the effect of smoking cessation. Differential cell counts and T cell subsets were determined in BAL fluid from nineteen individuals with stable COPD (seven smokers, twelve ex-smokers) compared to twelve age-matched never-smokers and thirteen smoking-matched smokers with normal lung function. COPD-patients had higher percentages of airway CD8(+) T cells compared to never-smokers. An increased population of CD4(+) T cells expressed high levels of CD25 in smokers and COPD patients compared to never-smokers, suggesting the presence of regulatory T cells. As the T cell populations in smokers with normal lung function and COPD-patients were similar, the impact of current smoking in COPD was addressed in a subgroup analysis. Activation of CD8(+) T cells was found regardless of smoking habits. In contrast, the enhanced expression of gamma/delta T cells, was mainly associated with current smoking, whilst the increase in T regulatory cells appeared related to both smoking and COPD. Regardless of smoking habits, CD8(+) T cell activation was found in COPD, supporting the contention that this T cell subset may play a role in the pathogenesis of COPD. As CD8(+) T cells coexist with immunoregulatory CD4(+) T cells in airways of COPD patients, it is likely that both cytotoxic T-cell responses and immunosuppressive mechanisms may be of importance in COPD pathogenesis.

Cigarette smoke-induced induction of antioxidant enzyme activities in airway leukocytes is absent in active smokers with COPD.

BACKGROUND: Oxidative injury to the airway has been proposed as an important underlying mechanism in the pathogenesis of chronic obstructive pulmonary disease (COPD). As the extent of oxidant-mediated damage is dependent on the endogenous antioxidant defences within the airways, we examined whether COPD was associated with deficiencies in the antioxidant network within the respiratory tract lining fluids (RTLFs) and resident airway leukocytes. We hypothesised that COPD would be associated with both basal depression of antioxidant defences and impaired adaptive antioxidant responses to cigarette smoke. METHODS: Low molecular weight and enzymatic antioxidants together with metal-handling proteins were quantified in bronchoalveolar lavage fluid and airway leukocytes, derived from current (n=9) and ex-smoking COPD patients (n=15), as well as from smokers with normal lung function (n=16) and healthy never smokers (n=13). RESULTS: Current cigarette smoking was associated with an increase in ascorbate and glutathione within peripheral RTLFs in both smokers with normal lung function compared with healthy never smokers and in COPD smokers compared with COPD ex-smokers. In contrast, intra-cellular antioxidant enzyme activities (glutathione peroxidase, glutathione reductase, and catalase) were only up-regulated in smokers with normal lung function compared with healthy never smokers and not in actively smoking COPD patients relative to COPD ex-smokers. CONCLUSIONS: We found no evidence of impaired basal antioxidant defences, within either the RTLFs or airway leukocytes in stable ex-smoking COPD patients compared with healthy never smoking controls. Current cigarette smoking induced an up-regulation of low molecular weight antioxidants in the RTLFs of both control subjects with normal lung function and patients with COPD. Importantly, the present data demonstrated a cigarette smoke-induced increase in intra-cellular antioxidant enzyme activities only within the smokers with normal lung function, implying that patients with COPD who continue to smoke will experience enhanced oxidative stress, prompting disease progression.

Identification of vitamin C transporters in the human airways: a cross-sectional in vivo study.

OBJECTIVES: Vitamin C is an important low-molecular weight antioxidant at the air-lung interface. Despite its critical role as a sacrificial antioxidant, little is known about its transport into the respiratory tract lining fluid (RTLF), or the underlying airway epithelial cells. While several vitamin C transporters have been identified, such as sodium-ascorbate cotransporters (SVCT1/2) and glucose transporters (GLUTs), the latter transporting dehydroascorbate, knowledge of their protein distribution within the human lung is limited, in the case of GLUTs or unknown for SVCTs. SETTING AND PARTICIPANTS: Protein expression of vitamin C transporters (SVCT1/2 and GLUT1-4) was examined by immunohistochemistry in endobronchial biopsies, and by FACS in airway leucocytes from lavage fluid, obtained from 32 volunteers; 16 healthy and 16 mild asthmatic subjects. In addition, antioxidant concentrations were determined in RTLF. The study was performed at one Swedish centre. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome measure was to establish the location of vitamin C transporters in the human airways. As secondary outcome measures, RTLF vitamin C concentration was measured and related to transporter expression, as well as bronchial epithelial inflammatory and goblet cells numbers. RESULTS: Positive staining was identified for SVCT1 and 2 in the vascular endothelium. SVCT2 and GLUT2 were present in the apical bronchial epithelium, where SVCT2 staining was predominately localised to goblet cells and inversely related to RTLF vitamin C concentrations. CONCLUSIONS: This experimental study is the first to demonstrate protein expression of GLUT2 and SVCT2 in the human bronchial epithelium. A negative correlation between SVCT2-positive goblet cells and bronchial RTLF vitamin C concentrations suggests a possible role for goblet cells in regulating the extracellular vitamin C pool.

Increased intraepithelial T-cells in stable COPD.

BACKGROUND: The airway epithelium is the first line of defence in the response to inhaled particles and irritants. Chronic obstructive pulmonary disease (COPD) is an inflammatory disease characterised by an irreversible loss of lung function, with cigarette smoking as a major risk factor. Here, we address intraepithelial T-cells in COPD, as these cells are a distinct T-cell subtype thought to have important regulatory functions. We hypothesised that intraepithelial T-cells play a role in the response to lung irritants and that the T-cell populations would be altered and associated with signs of inflammation in COPD. METHODS: Bronchoscopy with endobronchial mucosal biopsy sampling was performed in 22 patients (mean age; 57) with stable COPD (median FEV(1)% predicted: 51). Age- and smoking- matched smokers (S) with normal lung function (n=14) and age-matched non-smokers (NS) (n=15) served as controls. Airway inflammation was recorded visually using bronchitis index (BI). Biopsy specimens were processed into glycol methacrylate resin and inflammatory cells were stained immunohistochemically. RESULTS: The number of intraepithelial CD4+ T-cells were significantly higher in COPD patients compared to smokers as well as trend towards significance in non-smokers (p=0.005 and p=0.036, respectively), whereas intraepithelial CD8+ T-cells number were increased in patients with COPD compared to non-smokers (p=0.017). Both patients with COPD and smokers had a higher BI than non-smokers (p<0.001 for both). CONCLUSIONS: The present data suggest a role for intraepithelial CD4+ and CD8+ T-cells in stable COPD and indicate that T-cells are of importance in the long-term inflammatory response in COPD or, alternatively, play a regulatory role.