Abnormal peripheral blood T-lymphocyte subsets in a subgroup of patients with COPD

Causal Role of Immune Cells in Chronic Obstructive Pulmonary Disease: A Two-Sample Mendelian Randomization Study

Accumulating evidence has highlighted the importance of immune cells in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, the understanding of the causal association between immunity and COPD remains incomplete due to the existence of confounding variables. In this study, we employed a two-sample Mendelian randomization (MR) analysis, utilizing the genome-wide association study database, to investigate the causal association between 731 immune-cell signatures and the susceptibility to COPD from a host genetics perspective. To validate the consistency of our findings, we utilized MR analysis results of lung function data to assess directional concordance. Furthermore, we employed MR-Egger intercept tests, Cochrane's Q test, MR-PRESSO global test, and "leave-one-out" sensitivity analyses to evaluate the presence of horizontal pleiotropy, heterogeneity, and stability, respectively. Inverse variance weighting results showed that seven immune phenotypes were associated with the risk of COPD. Analyses of heterogeneity and pleiotropy analysis confirmed the reliability of MR results. These results highlight the interactions between the immune system and the lungs. Further investigations into their mechanisms are necessary and will contribute to inform targeted prevention strategies for COPD.

The predictive value of baseline symptom score and the peripheral CD4CD8 double-positive T cells in patients with AECOPD

BACKGROUND

Accurate prediction of acute exacerbation helps select patients with chronic obstructive pulmonary disease (COPD) for individualized therapy. The potential of lymphocyte subsets to function as clinical predictive factors for acute exacerbations of chronic obstructive pulmonary disease (AECOPD) remains uncertain.

METHODS

In this single-center prospective cohort study with a 2-year follow-up, 137 patients aged 51 to 79 with AECOPD were enrolled. We examined the prognostic indicators of AECOPD by analyzing lymphocyte subsets and baseline symptom score. Furthermore, a predictive model was constructed to anticipate the occurrence of respiratory failure in patients experiencing AECOPD.

RESULTS

The COPD Assessment Test (CAT) score combined with home oxygen therapy and CD4+CD8+ T cells% to predict respiratory failure in AECOPD patients were the best (the area under the curves [AUC] = 0.77, 95% CI: 0.70-0.86, P < 0.0001, sensitivity: 60.4%, specificity: 86.8%). The nomogram model, the C index, calibration plot, decision curve analysis, and clinical impact curve all indicate the model's good predictive performance. The observed decrease in the proportions of CD4+CD8+ T cells appears to be correlated with more unfavorable outcomes.

CONCLUSIONS

The nomogram model, developed to forecast respiratory failure in patients with AECOPD, utilizing variables such as home oxygen therapy, CAT score, and CD4+CD8+ T cells%, demonstrated a high level of practicality in clinical settings. CD4+CD8+ T cells serve as a reliable and readily accessible predictor of AECOPD, exhibiting greater stability compared to other indices. It is less susceptible to subjective influences from patients or physicians. This model facilitated personalized estimations, enabling healthcare professionals to make informed decisions regarding preventive interventions.

Ebselen prevents cigarette smoke-induced gastrointestinal dysfunction in mice

Gastrointestinal (GI) dysfunction is a common comorbidity of chronic obstructive pulmonary disease (COPD) for which a major cause is cigarette smoking (CS). The underlying mechanisms and precise effects of CS on gut contractility, however, are not fully characterised. Therefore, the aim of the present study was to investigate whether CS impacts GI function and structure in a mouse model of CS-induced COPD. We also aimed to investigate GI function in the presence of ebselen, an antioxidant that has shown beneficial effects on lung inflammation resulting from CS exposure. Mice were exposed to CS for 2 or 6 months. GI structure was analysed by histology and immunofluorescence. After 2 months of CS exposure, ex vivo gut motility was analysed using video-imaging techniques to examine changes in colonic migrating motor complexes (CMMCs). CS decreased colon length in mice. Mice exposed to CS for 2 months had a higher frequency of CMMCs and a reduced resting colonic diameter but no change in enteric neuron numbers. Ten days cessation after 2 months CS reversed CMMC frequency changes but not the reduced colonic diameter phenotype. Ebselen treatment reversed the CS-induced reduction in colonic diameter. After 6 months CS, the number of myenteric nitric-oxide producing neurons was significantly reduced. This is the first evidence of colonic dysmotility in a mouse model of CS-induced COPD. Dysmotility after 2 months CS is not due to altered neuron numbers; however, prolonged CS-exposure significantly reduced enteric neuron numbers in mice. Further research is needed to assess potential therapeutic applications of ebselen in GI dysfunction in COPD.

Glucagon-like peptide-1 receptor (GLP-1R) signaling ameliorates dysfunctional immunity in COPD patients

Background

The glucagon-like peptide-1 receptor (GLP-1R) agonist – liraglutide (LIR) – is an insulin secretagogue for the treatment of diabetes and has been proven to have therapeutic potential in the treatment of COPD. Evidence suggested that activating GLP-1R signaling might have immunomodulating and anti-inflammatory effects. COPD is characterized by dysregulation of immunity, oxidative stress, and excessive inflammation responses. The aim of this study was to investigate whether GLP-1R signaling had a regulatory role in COPD immunity.

Patients and methods

Fifty-seven COPD patients in a stable condition and 51 age-, sex-, and smoking history-matched non-COPD subjects provided blood samples for isolation of peripheral blood mononuclear cells (PBMCs). GLP-1R expression was measured, and its association with clinical parameters and plasma cytokines was analyzed. T cell function was assessed at baseline and after regulating GLP-1R expression.

Results

GLP-1R expression decreased in circulating PBMCs of COPD patients, which was associated with decreased interferon (IFN)-γ expression. Reduced IFN-γ production stimulated by phytohemagglutinin (PHA) and increased programmed cell death protein 1 (PD-1) expression on T cells were observed in COPD patients compared with non-COPD subjects. Treatment with LIR could upregulate the GLP-1R expression, and this was observed to restore the antigen-stimulated IFN-γ production and downregulate PD-1 expression in T cells.

Conclusion

PBMCs of COPD patients showed defective GLP-1R signaling and functional T-lymphocyte abnormalities that could be rescued by LIR treatment.

Immune cell response to strenuous resistive breathing: comparison with whole body exercise and the effects of antioxidants

Background/hypothesis

Whole body exercise (WBE) changes lymphocyte subset percentages in peripheral blood. Resistive breathing, a hallmark of diseases of airway obstruction, is a form of exercise for the inspiratory muscles. Strenuous muscle contractions induce oxidative stress that may mediate immune alterations following exercise. We hypothesized that inspiratory resistive breathing (IRB) alters peripheral blood lymphocyte subsets and that oxidative stress mediates lymphocyte subpopulation alterations following both WBE and IRB.

Patients and methods

Six healthy nonathletes performed two WBE and two IRB sessions for 45 minutes at 70% of VO₂ maximum and 70% of maximum inspiratory pressure (Pi_max), respectively, before and after the administration of antioxidants (vitamins E, A, and C for 75 days, allopurinol for 30 days, and N-acetylcysteine for 3 days). Blood was drawn at baseline, at the end of each session, and 2 hours into recovery. Lymphocyte subsets were determined by flow cytometry.

Results

Before antioxidant supplementation at both WBE end and IRB end, the natural killer cell percentage increased, the T helper cell (CD3+ CD4+) percentage was reduced, and the CD4/CD8 ratio was depressed, a response which was abolished by antioxidants only after IRB. Furthermore, at IRB end, antioxidants promoted CD8+ CD38+ and blunted cytotoxic T-cell percentage increase. CD8+ CD45RA+ cell percentage changes were blunted after antioxidant supplementation in both WBE and IRB.

Conclusion

We conclude that IRB produces (as WBE) changes in peripheral blood lymphocyte subsets and that oxidative stress is a major stimulus predominantly for IRB-induced lymphocyte subset alterations.

A Low Peripheral Blood CD4/CD8 Ratio Is Associated with Pulmonary Emphysema in HIV

OBJECTIVES

The prevalence of emphysema is higher among HIV-infected (HIV+) individuals compared to HIV-uninfected persons. While greater tobacco use contributes, HIV-related effects on immunity likely confer additional risk. Low peripheral blood CD4+ to CD8+ T-lymphocyte (CD4/CD8) ratio may reflect chronic inflammation in HIV and may be a marker of chronic lung disease in this population. Therefore, we sought to determine whether the CD4/CD8 ratio was associated with chronic obstructive pulmonary disease (COPD), particularly the emphysema subtype, in a cohort of HIV+ subjects.

METHODS

We performed a cross-sectional analysis of 190 HIV+ subjects enrolled in the Examinations of HIV Associated Lung Emphysema (EXHALE) study. Subjects underwent baseline laboratory assessments, pulmonary function testing and chest computed tomography (CT) analyzed for emphysema severity and distribution. We determined the association between CD4/CD8 ratio and emphysema, and the association between CD4/CD8 ratio and pulmonary function markers of COPD.

RESULTS

Mild or greater emphysema (>10% lung involvement) was present in 31% of subjects. Low CD4/CD8 ratio was associated with >10% emphysema in multivariable models, adjusting for risk factors including smoking, current and nadir CD4 count and HIV RNA level. Those with CD4/CD8 ratio <0.4 had 6.3 (1.1-39) times the odds of >10% emphysema compared to those with a ratio >1.0 in fully adjusted models. A low CD4/CD8 ratio was also associated with reduced diffusion capacity (DLCO).

CONCLUSIONS

A low CD4/CD8 ratio was associated with emphysema and low DLCO in HIV+ subjects, independent of other risk factors and clinical markers of HIV. The CD4/CD8 ratio may be a useful, clinically available, marker for risk of emphysema in HIV+ subjects in the antiretroviral therapy (ART) era.

Timely blockade of ICAM-1.LFA-1 interaction prevents disease onset in a mouse model of emphysema

AIM

It is becoming apparent that emphysema is partly driven by self-reactive T cells inducing inflammatory damage. Thus, T cells become targets for therapy similar to other autoimmune diseases. Costimulatory blockade therapy targets disease-specific T cells, rendering them ineffective by blocking a necessary costimulatory event on the T-cell surface. This therapy is tested here in mouse emphysema.

MATERIALS & METHODS

Peptides representing contact domains of counter receptors LFA-1 and ICAM-1 were used as blockade therapy in elastase-induced emphysema.

RESULTS

When administered during the first week after disease induction, blockade prevented lung destruction, reduced leukocyte infiltration and inhibited the decrease in T-cell CD4:CD8 ratio, also common in human emphysema.

CONCLUSION

Costimulatory blockade therapy can affect the progress of emphysema.

Peripheral Blood T-Cell Populations in COPD, Asymptomatic Smokers and Healthy Non-Smokers in Indian subpopulation- A Pilot Study

BACKGROUND

COPD is a major global health problem affecting 4-10% of Indian adult male population. Immunological processes have been implicated in the pathogenesis of COPD. As compared to healthy smokers, COPD patients have airway inflammation indicated by the presence of CD8+ T cells in the lung. This predominant increase in CD8+ T cells in the lung may be reflected in the peripheral blood. In an attempt to understand why only some smokers develop COPD, we compared the peripheral T-cell markers in COPD patients with that of asymptomatic smokers, and healthy nonsmokers.

METHODS

Twenty healthy non-smokers (HNS), 19 asymptomatic smokers (AS) and 21 COPD male patients (age and pack year-matched) were identified after clinical evaluation and spirometry. Blood CD3+, CD4+, CD8+ T-cell populations were measured.

RESULTS

Smokers with COPD had severe airflow limitation (FVC, 69.8+16.7%; FEV1, 47.47+16.9%; FEV1/FVC, 53.1+13.3%). The BMI was found to be significantly lower among patients with COPD (19.1+4.8kg/m(2)) as compared to AS (23+4.3kg/m(2)) and HNS (23.7+4.0kg/m(2)) (p value = 0.003 HS). The mean CD3+T-cell absolute count in COPD patients (1154.3+582.2), showed a marked decline as compared to that of AS (1251.9+491.6) and HNS (1424.9+352.2). The mean CD4+T-cell counts in COPD patients (652.7+340.5) were also lower when compared to AS (745.7+313.8) and HNS (832.5+220.7). The mean CD8+T-cell counts among COPD patients (424.7+264.3) were, similar to the counts observed among AS (426.9+193.2) and HNS (500.4+191). Though not statistically significant, the absolute counts of CD3+, CD4+ and CD8+ lymphocytes among COPD patients tended to be lower. No significant difference in the CD4+/CD8+ lymphocyte ratio between the patient groups was observed.

CONCLUSION

Our study indicates that BMI is related to the severity of COPD, hence proving a systemic component to its pathogenesis. However, we found similar percentages of CD8+Tcells in all the study groups suggesting that predominant CD8+ T cells in the airways may be due to its de novo origin rather than recruitment from blood. However, larger studies are needed to clarify the effect of disease severity, beedi smoking and ethnicity.

Increased cytokines response in patients with tuberculosis complicated with chronic obstructive pulmonary disease

Objectives

To explore the change and its significance of cytokines in patients with pulmonary tuberculosis complicated with COPD.

Methods

The immune function of 152 cases of pulmonary tuberculosis with COPD was detected to compare with 150 cases of patients with pulmonary tuberculosis, 157 cases of patients with COPD and 50 cases of healthy volunteers who were in the hospital during the same period. T lymphocyte cell population in peripheral blood was detected by flow cytometry. The serum levels of sIL-2R, IL-6, IFN-γ, TNF-α were measured using ELISA.

Results

The percentage of CD4+ T cells in TB patients with or without COPD and COPD patients without TB was significantly lower than that in control group. The percentage of CD4+ T cells in patients with TB and COPD was significantly lower than that in the non-COPD TB patients. The percentage of CD8+ T cells was higher in the TB patients group than that in control group. The CD4+/CD8+ ratio in the TB patients group was significantly lower than that in control group. The concentrations of sIL-2R, IL-6, TNF-α, IFN-γ in TB patients with or without COPD and COPD patients without TB were significantly higher than those in control group. In addition, sIL-2R, IL-6, TNF-α concentrations in the patients with TB and COPD were higher than those in the non-COPD TB patients. The concentrations of sIL-2R, IL-6, TNF-α, IFN-γ in COPD patients with TB were significantly higher than those in COPD patients without TB. There was a significant negative correlation between serum levels of TNF-α, IL-6 and FEV1 (%, predicted) in COPD without TB group.

Conclusions

The patients with pulmonary tuberculosis complicated with COPD were impaired in cellular immunity, and its extent of immune impairment is more serious than those of the patients with pulmonary tuberculosis and the patients with COPD.

Differential activation of killer cells in the circulation and the lung: a study of current smoking status and chronic obstructive pulmonary disease (COPD)

BACKGROUND

CD8(+) T-lymphocytes, natural killer T-like cells (NKT-like cells, CD56(+)CD3(+)) and natural killer cells (NK cells, CD56(+)CD3(-)) are the three main classes of human killer cells and they are implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Activation of these cells can initiate immune responses by virtue of their production of inflammatory cytokines and chemokines that cause lung tissue damage, mucus hypersecretion and emphysema. The objective of the current study was to investigate the activation levels of human killer cells in healthy non-smokers, healthy smokers, ex-smokers with COPD and current smokers with COPD, in both peripheral blood and induced sputum.

METHODS/PRINCIPAL FINDINGS

After informed consent, 124 participants were recruited into the study and peripheral blood or induced sputum was taken. The activation states and receptor expression of killer cells were measured by flow cytometry. In peripheral blood, current smokers, regardless of disease state, have the highest proportion of activated CD8(+) T-lymphocytes, NKT-like cells and NK cells compared with ex-smokers with COPD and healthy non-smokers. Furthermore, CD8(+) T-lymphocyte and NK cell activation is positively correlated with the number of cigarettes currently smoked. Conversely, in induced sputum, the proportion of activated killer cells was related to disease state rather than current smoking status, with current and ex-smokers with COPD having significantly higher rates of activation than healthy smokers and healthy non-smokers.

CONCLUSIONS

A differential effect in systemic and lung activation of killer cells in COPD is evident. Systemic activation appears to be related to current smoking whereas lung activation is related to the presence or absence of COPD, irrespective of current smoking status. These findings suggest that modulating killer cell activation may be a new target for the treatment of COPD.

Imbalance of circulating T-lymphocyte subpopulation in COPD and its relationship with CAT performance

Chronic obstructive pulmonary disease (COPD) is associated with systemic effects, and T-cell-mediated immunity was involved in the COPD. COPD Assessment Test (CAT) could provide a valid, reliable, and standardized measure of COPD health status. The objective of this study was determination of lymphocyte subpopulation in patients with stable COPD (n = 52) and to ascertain if a relationship existed between T-lymphocyte subpopulation and CAT performance. The stable COPD patients were assessed with CAT, and divided into four groups with score >30 (n = 8), 20< score ≤30 (n = 16), 10< score ≤20 (n = 20), and score ≤10 (n = 8). Spearman's rank correlation was used to determine the relationship between proportion of T lymphocyte and CAT score. We found an elevated proportion of CD8(+) cells in COPD patients of the group with score >30 compared to other groups. Proportion of CD4(+) cells was significantly lower in the groups with score >30 and 20< score ≤30 when compared to groups with 10< score ≤20 and score ≤10. The CD4(+) :CD8(+) ratio was also significantly lower in the groups with score >30 and 20< score ≤30. Of note are the correlations of proportion of CD8(+) cells and CD4(+) :CD8(+) ratio with CAT performance when score >20. No correlations existed between proportion of CD4(+) , CD8(+) cells, CD4(+) :CD8(+) ratio, and CAT performance when score ≤20. Our results show that the determinants of T-lymphocyte subpopulation in COPD patients were value to assess physical conditions. We considered CD4(+) and CD8(+) T lymphocytes to be a representative and stable parameter in grading of health status in COPD patients.

Correlation between peripheral blood T-cell profiles and clinical and inflammatory parameters in stable COPD

BACKGROUND

Recent studies suggest that Tc1/Tc2 imbalances are implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). The purpose of this study was to clarify the relationship between peripheral blood T-cell profiles and pulmonary function or inflammatory parameters.

METHODS

Thirty-one patients with stable COPD (median age 70 years, 30 males, 15 current smokers and 16 ex-smokers) and 30 healthy control subjects were enrolled in this study. The subjects underwent blood tests, exhaled nitric oxide (eNO) measurement, pulmonary function tests, and sputum induction. Tc1/Tc2 and Th1/Th2 were determined by analyzing intracellular cytokine staining for IFN-gamma and IL-4 in peripheral blood CD8+ and CD4+ T cells using flow cytometry after stimulation with phorbol 12-myristate 13-acetate and ionomycin.

RESULTS

There was a significantly increased proportion of IFN-gamma-producing and IL-4-producing CD8+ T cells in patients with COPD compared with control subjects (median [IQR] 73.6% [63.9%-80.7%] vs 62.0% [45.6%-73.8%], p=0.004; and 2.6% [1.1%-6.9%] vs 1.1% [0.6%-2.2%], p=0.002, respectively). In addition, the proportion of IFN-gamma-producing CD4+ T cells was significantly higher in patients with COPD compared with control subjects (25.7% [21.2%-38.0%] vs 22.8% [15.6%-29.2%], p=0.027). The proportion of IFN-gamma-producing CD8+ T cells was correlated negatively with single-breath carbon monoxide transfer coefficient (Kco)(rho=-0.45, p=0.033) and positively with eNO (rho=0.50, p=0.012). The proportion of IL-4-producing CD8+ T cells was positively correlated with body mass index (rho=0.42, p=0.023) and Kco (rho=0.47, p=0.026).

CONCLUSIONS

It is suggested that Tc1 cells have a detrimental role and that Tc2 cells have a protective role in disease progression.

Altered effector function of peripheral cytotoxic cells in COPD

Background

There is mounting evidence that perforin and granzymes are important mediators in the lung destruction seen in COPD. We investigated the characteristics of the three main perforin and granzyme containing peripheral cells, namely CD8⁺ T lymphocytes, natural killer (NK; CD56⁺CD3^-) cells and NKT-like (CD56⁺CD3⁺) cells.

Methods

Peripheral blood mononuclear cells (PBMCs) were isolated and cell numbers and intracellular granzyme B and perforin were analysed by flow cytometry. Immunomagnetically selected CD8+ T lymphocytes, NK (CD56⁺CD3^-) and NKT-like (CD56⁺CD3⁺) cells were used in an LDH release assay to determine cytotoxicity and cytotoxic mechanisms were investigated by blocking perforin and granzyme B with relevant antibodies.

Results

The proportion of peripheral blood NKT-like (CD56⁺CD3⁺) cells in smokers with COPD (COPD subjects) was significantly lower (0.6%) than in healthy smokers (smokers) (2.8%, p < 0.001) and non-smoking healthy participants (HNS) (3.3%, p < 0.001). NK (CD56⁺CD3^-) cells from COPD subjects were significantly less cytotoxic than in smokers (16.8% vs 51.9% specific lysis, p < 0.001) as were NKT-like (CD56⁺CD3⁺) cells (16.7% vs 52.4% specific lysis, p < 0.001). Both cell types had lower proportions expressing both perforin and granzyme B. Blocking the action of perforin and granzyme B reduced the cytotoxic activity of NK (CD56⁺CD3^-) and NKT-like (CD56⁺CD3⁺) cells from smokers and HNS.

Conclusion

In this study, we show that the relative numbers of peripheral blood NK (CD56⁺CD3^-) and NKT-like (CD56⁺CD3⁺) cells in COPD subjects are reduced and that their cytotoxic effector function is defective.

Peripheral T cell functions correlate with the severity of chronic obstructive pulmonary disease

Adaptive immune processes have been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). We hypothesized that peripheral T cell abnormalities may be present in afflicted patients. We tested this hypothesis by characterizing circulating T cells in COPD patients and correlated these findings with disease severity, smoking status, and use of inhaled glucocorticosteroids (ICS). Compared with normal controls, a lesser proportion of peripheral CD4 T cells from COPD subjects produced IL-10, whereas the CD8 T cells from these patients were more often activated and more frequently produced both IFN-gamma and IL-4. COPD severity was significantly and inversely associated with the proportion of circulating CD4 T cells and directly correlated with CD4 production of IL-2, as well as frequency of CD8 T cell activation and CD8 IFN-gamma production. Adjustments for current smoking status and ICS use by linear regression showed independent, and generally inhibitory, effects of these clinical variables on the abnormal T cell functions of these patients. We conclude that circulating T cells from COPD patients are abnormally activated and elaborate proinflammatory mediators with admixed features of Th1 and Th2 responses. Furthermore, many of these effector processes are significantly correlated with disease severity. These findings further implicate adaptive immune processes in COPD progression and indicate that facile assays of peripheral lymphocytes may provide useful insights into disease mechanisms. Current smoking and ICS use had independent effects on T cell functions among the COPD subjects, illustrating the importance of controlling for clinical parameters as covariates in immunological studies of patients afflicted with this disease.

Enhanced acute responses in an experimental exposure model to biomass smoke inhalation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary diseases (COPD) may increase air pollution-related mortality. The relationship of immune mechanisms to mortality caused by fine particulates in healthy and COPD populations is incompletely understood. The objective of this study was to determine whether fine particulates from a single biomass fuel alter stress and inflammation biomarkers in people with COPD. Healthy and COPD subjects were exposed to smoke in a controlled indoor setting. Immune responses were quantified by measuring cell surface marker expression with flow-cytometric analysis and mRNA levels with quantitative reverse transcriptase-polymerase chain reactions in whole blood before and after exposure. Preexposure COPD subjects had more leukocytes, mainly CD14(+) monocytes and neutrophils, but fewer CD3(+) T cells. Fifty-seven of 186 genes were differentially expressed between healthy and COPD subjects' peripheral blood mononuclear cells (PBMCs). Of these, only nuclear factor (NF)-kappa B1, TIMP-1, TIMP-2, and Duffy genes were up-regulated in COPD subjects. At 4 hours post smoke exposure, monocyte levels decreased only in healthy subjects. Fifteen genes, particular to inflammation, immune response, and cell-to-cell signaling, were differentially expressed in COPD subjects, versus 4 genes in healthy subjects. The authors observed significant differences in subjects' PBMCs, which may elucidate the adverse effects of air pollution particulates on people with COPD.

Killer cells in chronic obstructive pulmonary disease

COPD (chronic obstructive pulmonary disease) is a treatable and preventable disease state, characterized by progressive airflow limitation that is not fully reversible. It is a current and growing cause of mortality and morbidity worldwide, with the WHO (World Health Organization) projecting that total deaths attributed to COPD will increase by more than 30% in the next 10 years. The pathological hallmarks of COPD are destruction of the lung parenchyma (pulmonary emphysema), inflammation of the central airways (chronic bronchitis) and inflammation of the peripheral airways (respiratory bronchiolitis). The destructive changes and tissue remodelling observed in COPD are a result of complex interactions between cells of the innate and adaptive immune systems. The focus of the present review is directed towards the role of CD8(+) T-lymphocytes, NK (natural killer) cells and NKT cells (NK T-cells). These three classes of killer cell could all play an important part in the pathogenesis of COPD. The observed damage to the pulmonary tissue could be caused in three ways: (i) direct cytotoxic effect against the lung epithelium mediated by the activities of perforin and granzymes, (ii) FasL (Fas ligand)-induced apoptosis and/or (iii) cytokine and chemokine release. The present review considers the role of these killer cells in COPD.

Frontiers in emphysema research

Chronic obstructive pulmonary disease (COPD) is a complex inflammatory disease with a myriad of pulmonary and nonpulmonary disease manifestations. COPD is a heterogeneous disease consisting of emphysematous destruction, airway inflammation, remodeling, and obstruction. Once conceptualized as a unidimensional disease isolated to the lung, it is now recognized to have significant systemic manifestations, such as osteoporosis, cardiovascular disease, and skeletal muscle wasting. As the clinical phenotypic expressions of COPD become more precisely characterized, so does the pathogenesis of this disease. Great strides are now being made in our understanding of genetic susceptibility, airway inflammation, the immune response to cigarette smoke, and inflammatory biomarkers. This review will discuss the most recent progress on selected topics in COPD pathogenesis, inflammation, and genetics. With time, we hope to expand our current understanding to predict who will develop disease and who will not, and why some patients develop particular disease phenotypes. In addition, we hope to clarify the inflammatory mechanisms involved in order to develop novel therapies and identify disease biomarkers that will lead to better tools for monitoring disease activity. Finally, we hope to develop treatments aimed at lung regeneration and repair, to reverse lung damage that has already occurred. We are optimistic that novel therapies like gene therapy and advanced antiinflammatory agents will be in our future. Judging by the progress made in the last decade, these tools may soon become a reality.

Pathogenesis of chronic obstructive pulmonary disease

The pathogenesis of chronic obstructive pulmonary disease (COPD) encompasses a number of injurious processes, including an abnormal inflammatory response in the lungs to inhaled particles and gases. Other processes, such as failure to resolve inflammation, abnormal cell repair, apoptosis, abnormal cellular maintenance programs, extracellular matrix destruction (protease/antiprotease imbalance), and oxidative stress (oxidant/antioxidant imbalance) also have a role. The inflammatory responses to the inhalation of active and passive tobacco smoke and urban and rural air pollution are modified by genetic and epigenetic factors. The subsequent chronic inflammatory responses lead to mucus hypersecretion, airway remodeling, and alveolar destruction. This article provides an update on the cellular and molecular mechanisms of these processes in the pathogenesis of COPD.

Acute exacerbations of chronic bronchitis in elderly patients: pathogenesis, diagnosis and management

Chronic bronchitis (CB) is a disorder that is characterised by chronic mucus production. This disorder is called chronic obstructive pulmonary disease (COPD) when airflow obstruction is present. The majority of patients with COPD, which often goes undiagnosed or inadequately treated in the elderly, have symptoms consistent with CB. The clinical course of CB is usually punctuated by periodic acute exacerbations linked to infections caused by viral and typical or atypical bacterial pathogens. Acute exacerbations of chronic bronchitis (AECB) often lead to a decline in lung function and poor quality of life in association with increased risk of mortality and a significant economic impact on the healthcare system and society because of the direct costs of hospitalisations. In elderly individuals with COPD, co-morbidities play a vital role as determinants of health status and prognosis. Failure to eradicate infecting pathogens contributes to persistence of infection and inflammation that requires repeated courses of therapy and hospitalisation. Stratifying patients with AECB according to symptoms, degree of pulmonary function impairment and risk factors for poor outcome can help clinicians choose empirical antimicrobial chemotherapy regimens that are most likely to result in treatment success. Failure to cover likely pathogens associated with episodes of AECB can lead to lengthy hospital admissions and significant declines in functional status for elderly patients. Fluoroquinolones may provide the best therapeutic option for elderly patients with COPD who have complicated underlying CB but who are sufficiently stable to be treated in the outpatient setting. Optimised treatment for stable outpatients with CB may diminish the frequency of AECB, and effective antimicrobial therapy for AECB episodes can significantly diminish healthcare costs and maintain quality of life in the elderly patient.

Perforin, granzyme B, and FasL expression by peripheral blood T lymphocytes in emphysema

BACKGROUND

It is generally accepted that emphysematous lungs are characterized by an increase in the numbers of neutrophils, macrophages, and CD8+ T lymphocytes, the lasts having increased cytotoxic activity. Because systemic inflammation is also a component of emphysema, we hypothesize that peripheral CD8+ T lymphocytes of emphysematous smokers who show evidence of systemic inflammation will have higher expression of cytotoxic molecules.

METHODS

We assessed parameters of systemic inflammation in normal individuals (smokers or non-smokers) and in emphysematous subjects with an active smoking history by measuring serum interleukine-6, C-reactive protein, and tumor necrosis factor. Expression of perforin, granzyme B, and FasL protein by CD8+ T lymphocytes, CD4+ T lymphocytes, and natural killer cells were assessed by flow cytometry while perforin, granzyme B, and FasL mRNA expression were measured on purified systemic CD8+ T lymphocytes by real-time PCR.

RESULTS

Emphysematous smokers had higher levels of serum interleukine-6 than normal subjects. Even with the presence of systemic inflammation in emphysematous smokers, the percentage of peripheral CD8+ T lymphocytes, CD4+ T lymphocytes, and NK cells expressing perforin and granzyme B protein was not different between the three groups.

CONCLUSION

Despite evidence of systemic inflammation, peripheral T lymphocytes of emphysematous smokers did not show higher levels of cytotoxic markers, suggesting that increase of activated T lymphocytes in the emphysematous lung may be due to either activation in the lung or specific peripheral recruitment.

Aspects on pathophysiological mechanisms in COPD

Chronic obstructive pulmonary disease (COPD) is a condition which is characterized by irreversible airway obstruction due to narrowing of small airways, bronchiolitis, and destruction of the lung parenchyma, emphysema. It is the fourth most common cause of mortality in the world and is expected to be the third most common cause of death by 2020. The main cause of COPD is smoking but other exposures may be of importance. Exposure leads to airway inflammation in which a variety of cells are involved. Besides neutrophil granulocytes, macrophages and lymphocytes, airway epithelial cells are also of particular importance in the inflammatory process and in the development of emphysema. Cell trafficking orchestrated by chemokines and other chamoattractants, the proteinase-antiproteinase system, oxidative stress and airway remodelling are central processes associated with the development of COPD. Recently systemic effects of COPD have attracted attention and the importance of systemic inflammation has been recognized. This seems to have direct therapeutic implications as treatment with inhaled glucocorticosteroids has been shown to influence mortality. The increasing body of knowledge regarding the inflammatory mechanism in COPD will most likely have implications for future therapy and new drugs, specifically aimed at interaction with the inflammatory processes, are currently being developed.

Increased intracellular T helper 1 proinflammatory cytokine production in peripheral blood, bronchoalveolar lavage and intraepithelial T cells of COPD subjects

The role of T cells in the pathophysiology of chronic obstructive pulmonary disease (COPD) is not yet certain, although varying reports have shown increases in T helper 1 (Th1) and/or Th2 cytokines in peripheral blood and bronchoalveolar lavage (BAL). No studies have examined cytokine production by intraepithelial T cells obtained by bronchial brushing (BB). Intracellular cytokine analysis of T cell subsets from peripheral blood, BAL and BB from smoker and ex-smoker COPD patients, COPD patients receiving inhaled corticosteroids and smoker and non-smoker control subjects was studied using multi-parameter flow cytometry. CD4 : CD8 inversion was noted in the peripheral blood of smoker and ex-smoker COPD groups, in BAL and BB from smoker controls and BAL of COPD smokers. There was an increase in intracellular CD8(+) T cell Th1 proinflammatory cytokines in some COPD groups in the peripheral blood and in CD8(+) T cell tumour necrosis factor (TNF)-alpha in some COPD groups and smoker controls in BAL and BB. There was an increase in proinflammatory cytokines in COPD smokers compared with ex-smokers and a decrease in COPD smokers receiving inhaled corticosteroids in the airways. There was a negative correlation between forced expiratory volume in 1 s (FEV(1)) and the percentage of BAL and intraepithelial CD8(+) T cells producing TNF-alpha. COPD patients exhibit systemic inflammation as evidenced by increased intracellular Th1 proinflammatory cytokines in blood, BAL and intraepithelial CD8(+) T cells, whereas smoker controls showed localized Th1 response in the lung only. Systemic therapeutic targeting of TNF-alpha production by CD8(+) T cells may improve morbidity in COPD patients while targeting of TNF-alpha in the lung may prevent smokers progressing to COPD.

Systemic effects of smoking

Smoking is one of the major lifestyle factors influencing the health of human beings. Life-long cigarette smokers have a higher prevalence of common diseases such as atherosclerosis and COPD with significant systemic impact. The present review evaluates current knowledge concerning possible pathways through which cigarette smoking can affect human health, with special focus on extrapulmonary effects. Long-term smoke exposure can result in systemic oxidants-antioxidants imbalance as reflected by increased products of lipid peroxidation and depleted levels of antioxidants like vitamins A and C in plasma of smokers. A low-grade systemic inflammatory response is evident in smokers as confirmed by numerous population-based studies: elevated levels of C-reactive protein (CRP), fibrinogen, and interleukin-6, as well as increased counts of WBC have been reported. Furthermore, rheologic, coagulation and endothelial function markers like hematocrit, blood and/or plasma viscosity, fibrin d-dimer, circulating adhesion molecules (intracellular adhesion molecule-1, selectins), tissue plasminogen activator antigen, and plasminogen activator inhibitor type I are altered in chronic cigarette smokers. Although most of smoking-induced changes are reversible after quitting, some inflammatory mediators like CRP are still significantly raised in ex-smokers up to 10 to 20 years after quitting, suggesting ongoing low-grade inflammatory response persisting in former smokers. New longitudinal epidemiologic and genetic studies are required to evaluate the role of smoking itself and possible gene/environment interplay in initiation and development of smoking-induced common diseases affecting humans.

T lymphocyte subset profile and serum alpha-1-antitrypsin in pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is an inflammatory disorder characterized by the presence of non-fully reversible airflow limitation. The study was undertaken to investigate the involvement of alpha-1-antitrypsin (alpha(1)AT) and T lymphocyte subsets in the pathogenesis of COPD. Blood samples of 50 subjects, including 25 healthy volunteers and 25 patients with COPD, were analysed. Serum trypsin inhibitory capacity (STIC) was determined by enzymatic assay. CD4(+) and CD8(+) T lymphocytes were enumerated in heparinized blood using a fluorescence activated cell sorter counter. The STIC in COPD patients was found to be decreased significantly than in controls (P < 0.01). In COPD patients with lower expression levels of alpha(1)AT, a highly significant decrease in the number of CD4(+) T lymphocytes (P < 0.0009) and CD4/CD8 ratio was observed compared with control subjects (P < 0.008). The mean +/- standard error of CD8(+) lymphocytes was found to be little different (only marginally decreased) in COPD patients compared to healthy controls; however, an alteration in the individual count of CD8(+) lymphocytes cells was observed in COPD patients. Using linear regression analysis, a negative correlation was observed between STIC and CD4(+) lymphocytes and CD8(+) lymphocytes (r = -0.40, P < 0.04; r = -0.42, P < 0.03, respectively) in COPD patients. An alteration in alpha(1)AT and T lymphocyte subsets in COPD patients suggested that interplay of these factors may be responsible for the progression of COPD.

Increased proportion of Fas positive CD8+ cells in peripheral blood of patients with COPD

Chronic obstructive pulmonary disease (COPD) is characterised by chronic inflammation in pulmonary tissue and is also associated with systemic effects. The objective of this study was determination of lymphocyte subpopulation and the expression of Fas receptor on lymphocytes derived from peripheral blood of patients with stable COPD (n=18) and a control group: asymptomatic smokers (n=12) and non-smokers (n=12). Flow cytometry method with monoclonal antibodies was used for evaluation of lymphocyte subsets: CD4+ and CD8+ and the expression of Fas (CD95) on T lymphocytes. We found an elevated proportion of CD8+ cells in the blood of COPD patients. Proportion of Fas+ T lymphocytes was significantly higher in patients with COPD when compared with asymptomatic smokers and non-smokers (mean: 84.4% vs. 71.6% vs. 61.0% for Fas+/ CD4+ and 88.1% vs. 73.8% vs. 58.3% for Fas+/CD8+ lymphocytes). The proportion of Fas positive CD8+ cells significantly correlated with the degree of airway obstruction and hypoxemia. The significant correlations of Fas positive CD4+ and Fas positive CD8+ with smoking history expressed as pack years smoked were observed. Our observation of an elevated proportion of circulating lymphocytes bearing Fas receptor may play a role in induction of these cells' apoptosis and indicate the role of Fas/ FasL pathway in the changes in proportion of lymphocyte subpopulations in patients with COPD.

Treatment With AM3 Restores Defective T-Cell Function in COPD Patients

BACKGROUND

Lymphocyte alterations have been associated with an increased prevalence of acute respiratory infections in COPD patients. AM3 is an oral immunomodulator that normalizes the defective functions of peripheral blood natural killer and phagocytic cells in COPD patients and improves their health-related quality of life.

OBJECTIVES

To characterize putative systemic abnormalities of the T-cell compartment in COPD patients, and to investigate whether AM3 can restore such abnormalities.

DESIGN

The study was a randomized, prospective, double-blind, placebo-controlled trial in a cohort of COPD patients. The results were also compared to those of nonsmoker and ex-smoker healthy control subjects.

SETTING

Outpatient departments of four hospitals.

PATIENTS

Seventy COPD patients were randomized to receive either AM3 or a placebo orally for 90 consecutive days. Populations of 36 healthy nonsmokers and 36 healthy ex-smokers were used as control subjects.

MEASUREMENTS

Peripheral blood mononuclear cell (PBMC) proliferation and production of interleukin (IL)-2, IL-4, IL-12p40, tumor necrosis factor-alpha, and interferon (IFN)-gamma proteins in response to the T-cell polyclonal mitogens were assessed at baseline and at the end of treatment.

RESULTS

The proliferative response was significantly decreased in COPD patients. Decreased production of IFN-gamma was the only defect in the profiles of the cytokine measures, and was selectively observed in COPD patients, but not in nonsmoker and ex-smoker healthy control subjects. Treatment with AM3 significantly restored the PBMC proliferative response to polyclonal mitogens and significantly promoted stimulated IFN-gamma production in these patients. The normalization of these proliferative responses was not related to significant variations in the numbers of peripheral blood monocytes, CD3+, CD4+, CD8+ cells or of any major naïve/memory/activated T-cell subset. The increased IFN-gamma production in the AM3 study arm was associated with an increase in the mean of number of IFN-gamma molecules produced per CD8+ T cells.

CONCLUSIONS

PBMCs of COPD patients showed clear functional T-lymphocyte abnormalities that are rescued by AM3 treatment.

Pathogenesis of chronic obstructive pulmonary disease

The current paradigm for the pathogenesis of chronic obstructive pulmonary disease is that chronic airflow limitation results from an abnormal inflammatory response to inhaled particles and gases in the lung. Airspace inflammation appears to be different in susceptible smokers and involves a predominance of CD8+ T lymphocytes, neutrophils, and macrophages. Studies have characterized inflammation in the peripheral airspaces in different stages of disease severity. Two other processes have received considerable research attention. The first is a protease-antiprotease imbalance, which has been linked to the pathogenesis of emphysema. However, the hypothesis of an increased protease burden associated with functional inhibition of antiproteases has been difficult to prove and is now considered an oversimplification. The second process, oxidative stress, has a role in many of the pathogenic processes of chronic obstructive pulmonary disease and may be one mechanism that enhances the inflammatory response. In addition, it has been proposed that the development of emphysema may involve alveolar cell loss through apoptosis. This mechanism may involve the vascular endothelial growth factor pathway and oxidative stress.

Laboratory markers for COPD in “susceptible” smokers

Smoking is the major risk factor for the development of chronic obstructive pulmonary disease. Apart from the important preventive steps of smoking cessation, there are no other specific treatments for COPD that are as effective in reversing the condition. However, only a relatively small proportion of smokers-about 15%-will develop clinically relevant COPD. Allergy, airway hyper-responsiveness (AHR) to methacholine, and gender differences have been proposed to identify individuals susceptible to the development of COPD. However, variable response to cigarette smoke clearly suggests genetic susceptibility. Among the COPD candidate genes are those (a) that effect the production of proteases and antiproteases, (b) modulate the metabolism of toxic substances in cigarette smoke, (c) are involved with mucocilliary clearance, and (d) that influence inflammatory mediators. Recently, sputum cells from smokers with and without COPD were tested for Microsatellite DNA Instability (MSI) with positive results. This finding suggests that MSI can be a useful marker of genetic susceptibility and thereby indicate destabilization of the genome in the "susceptible" smoker. Nevertheless, COPD lacks established viable biomarkers to predict and monitor disease progression and outcome variables. Such monitoring tools may be induced sputum, exhaled air condensate, peripheral blood, urine, bronchial biopsies, and bronchoalveolar lavage fluid (BALF). This review summarizes recent research on potential laboratory markers in smokers and subsequent COPD development.

Systemic CD4+ T-cell activation is correlated with FEV1 in smokers

The inflammation of the lungs in chronic obstructive pulmonary disease (COPD) is characterised by increased numbers of macrophages, neutrophils and T-cells. Decline in lung function in these patients has been correlated to the number of CD8+ T-cells present in the lung as well as to a decline in the ratio of CD4+/CD8+ T-cells. Although systemic components are likely to be present, circulating lymphocyte populations in COPD patients have not been well characterised. This study aimed at correlating lung function to expression of five different T-cell activation markers on peripheral blood CD4+ and CD8+ T-cells in COPD patients and matched smokers. Furthermore, proportions of lymphocyte populations and degree of systemic T-cell activation in COPD patients were compared to that in smokers and never-smokers. Peripheral blood lymphocytes from six never-smokers, eight smokers and 17 smokers with COPD were analysed using flowcytometry. The number of lymphocytes per millilitre was higher in smokers than in never-smokers. No differences were found between the three groups in regard to proportions of lymphocyte populations, but the number of CD4+ T-cells in smokers was higher than in both never-smokers and COPD patients. The degree of T-cell activation was similar in all patient groups; however, a clear correlation between CD69 expression on CD4+ T-cells and lung function (FEV(1)% of predicted) was found when examining current smokers, with or without COPD. Elevated numbers of CD69+ CD4+ T-cells in blood thus seem to be protective against airway obstruction in smokers while still exposed to cigarette smoke, the main inducer of COPD.

Mediators of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major and increasing global health problem that is now a leading cause of death. COPD is associated with a chronic inflammatory response, predominantly in small airways and lung parenchyma, which is characterized by increased numbers of macrophages, neutrophils, and T lymphocytes. The inflammatory mediators involved in COPD have not been clearly defined, in contrast to asthma, but it is now apparent that many lipid mediators, inflammatory peptides, reactive oxygen and nitrogen species, chemokines, cytokines, and growth factors are involved in orchestrating the complex inflammatory process that results in small airway fibrosis and alveolar destruction. Many proteases are also involved in the inflammatory process and are responsible for the destruction of elastin fibers in the lung parenchyma, which is the hallmark of emphysema. The identification of inflammatory mediators and understanding their interactions is important for the development of anti-inflammatory treatments for this important disease.

Impact of tobacco smoke on interleukin-16 protein in human airways, lymphoid tissue and T lymphocytes

CD4(+) and CD8(+) lymphocytes are mobilized in severe chronic obstructive pulmonary disease (COPD) and the CD8(+) cytokine interleukin (IL)-16 is believed to be important in regulating the recruitment and activity of CD4(+) lymphocytes. In the current study, we examined whether tobacco smoke exerts an impact not only on IL-16 in the lower airways but also in CD4(+) or CD8(+) lymphocytes or in lymphoid tissue. The concentration of IL-16 protein was measured by enzyme-linked immunosorbent assay (ELISA) in concentrated bronchoalveolar lavage fluid (BALF) collected from 33 smokers with chronic bronchitis (CB), eight asymptomatic smokers (AS) and seven healthy never-smokers (NS). The concentrations of IL-16 and soluble IL-2 receptor alpha (sIL-2Ralpha) protein were also measured in conditioned medium from human blood CD4(+) and CD8(+) lymphocytes stimulated with tobacco smoke extract (TSE) in vitro. IL-16 mRNA was assessed in vitro as well, using reverse transcription-polymerase chain reaction (RT-PCR). Finally, the intracellular immunoreactivity for IL-16 protein (IL-16IR) was assessed in six matched pairs of palatine tonsils from smokers and non-smokers. BALF IL-16 was higher in CB and AS than in NS. TSE substantially increased the concentration of IL-16 but not sIL-2Ralpha in conditioned medium from CD4(+) and CD8(+) lymphocytes. There was no corresponding effect on IL-16 mRNA. IL-16IR in tonsils was lower in smokers than in non-smokers. The current findings demonstrate that tobacco smoke exerts a wide impact on the CD8(+) cytokine IL-16, in the airway lumen, in blood CD4(+) and CD8(+) lymphocytes and in lymphoid tissue. The effect on IL-16 release may be selective for preformed IL-16 in CD4(+) lymphocytes. New clinical studies are required to evaluate whether tobacco smoke mobilizes T lymphocytes via IL-16 in the lower airways and whether this mechanism can be targeted in COPD.