Clinical utility of bronchoalveolar lavage cell phenotype analyses in the postoperative monitoring of lung transplant recipients

The CD8+ T cell content of transbronchial biopsies from patients with a first episode of clinically stable grade A1 cellular rejection is associated with future chronic lung allograft dysfunction

BACKGROUND

T cells drive acute cellular rejection (ACR) and its progression to chronic lung allograft dysfunction (CLAD) following lung transplantation. International Society for Heart and Lung Transplantation grade A1 ACR without associated allograft dysfunction is often untreated, yet some patients develop progressive graft dysfunction. T-cell composition of A1 ACR lesions may have prognostic value; therefore, protein-level and epigenetic techniques were applied to transbronchial biopsy tissue to determine whether differential T-cell infiltration in recipients experiencing a first episode of stable grade A1 ACR (StA1R) is associated with early CLAD.

METHODS

Sixty-two patients experiencing a first episode of StA1R were divided into those experiencing CLAD within 2 years (n = 13) and those remaining CLAD-free for 5 or more years (n = 49). Imaging mass cytometry (IMC) was used to profile the spectrum and distribution of intragraft T cell phenotypes on a subcohort (n = 16; 8 early-CLAD and 8 no early-CLAD). Immunofluorescence was used to quantify CD4+, CD8+, and FOXP3+ cells. Separately, CD3+ cells were fluorescently labeled, micro-dissected, and the degree of Treg-specific demethylated region methylation was determined.

RESULTS

PhenoGraph unsupervised clustering on IMC revealed 50 unique immune cell subpopulations. Methylation and immunofluorescence analyses demonstrated no significant differences in Tregs between early-CLAD and no early-CLAD groups. Immunofluorescence revealed that patients who developed CLAD within 2 years of lung transplantation showed greater CD8+ T cell infiltration compared to those who remained CLAD-free for 5 or more years.

CONCLUSIONS

In asymptomatic patients with a first episode of A1 rejection, greater CD8+ T cell content may be indicative of worse long-term outlook.

Fungal Tracheobronchitis in Lung Transplant Recipients: Incidence and Utility of Diagnostic Markers

Fungal tracheobronchitis caused by Aspergillus and Candida spp. is a recognized complication after lung transplantation, but knowledge of the incidence of Candida tracheobronchitis is lacking. The diagnosis relies on fungal cultures in bronchoalveolar lavage fluid (BALF), but cultures have low specificity. We aimed to evaluate the one-year incidence of fungal tracheobronchitis after lung transplantation and to assess the utility of diagnostic markers in serum and BALF to discriminate fungal tracheobronchitis from colonization. Ninety-seven consecutively included adult lung-transplant recipients were prospectively followed. BALF and serum samples were collected at 1, 3 and 12 months after transplantation and analyzed for betaglucan (serum and BALF), neutrophils (BALF) and galactomannan (BALF). Fungal tracheobronchitis was defined according to consensus criteria, modified to include Candida as a mycologic criterion. The cumulative one-year incidence of Candida and Aspergillus tracheobronchitis was 23% and 16%, respectively. Neutrophils of >75% of total leukocytes in BALF had 92% specificity for Candida tracheobronchitis. The area under the ROC curves for betaglucan and galactomannan in BALF to discriminate Aspergillus tracheobronchitis from colonization or no fungal infection were high (0.86 (p < 0.0001) and 0.93 (p < 0.0001), respectively). To conclude, the one-year incidence of fungal tracheobronchitis after lung transplantation was high and dominated by Candida spp. Diagnostic markers in BALF could be useful to discriminate fungal colonization from tracheobronchitis.

Effector immune cells in Chronic Lung Allograft Dysfunction: a Systematic Review

Chronic lung allograft dysfunction (CLAD) remains the major barrier to long‐term survival after lung transplantation and improved insight into its underlying immunological mechanisms is critical to better understand the disease and to identify treatment targets. We systematically searched the electronic databases of PubMed and EMBASE for original research publications, published between January 2000 and April 2021, to comprehensively assess current evidence on effector immune cells in lung tissue and bronchoalveolar lavage fluid from lung transplant recipients with CLAD. Literature search revealed 1351 articles, 76 of which met the criteria for inclusion in our analysis. Our results illustrate significant complexity in both innate and adaptive immune cell responses in CLAD, along with presence of numerous immune cell products, including cytokines, chemokines and proteases associated with tissue remodelling. A clear link between neutrophils and eosinophils and CLAD incidence has been seen, in which eosinophils more specifically predisposed to restrictive allograft syndrome. The presence of cytotoxic and T‐helper cells in CLAD pathogenesis is well‐documented, although it is challenging to draw conclusions about their role in tissue processes from predominantly bronchoalveolar lavage data. In restrictive allograft syndrome, a more prominent humoral immune involvement with increased B cells, immunoglobulins and complement deposition is seen. Our evaluation of published studies over the last 20 years summarizes the complex multifactorial immunopathology of CLAD onset and progression. It highlights the phenotype of several key effector immune cells involved in CLAD pathogenesis, as well as the paucity of single cell resolution spatial studies in lung tissue from patients with CLAD.

Chronic Lung Allograft Dysfunction: Review of CT and Pathologic Findings

Chronic lung allograft dysfunction (CLAD) is the most common cause of mortality in lung transplant recipients after the 1st year of transplantation. CLAD has traditionally been classified into two distinct obstructive and restrictive forms: bronchiolitis obliterans syndrome and restrictive allograft syndrome. However, CLAD may manifest with a spectrum of imaging and pathologic findings and a combination of obstructive and restrictive physiologic abnormalities. Although the initial CT manifestations of CLAD may be nonspecific, the progression of findings at follow-up should signal the possibility of CLAD and may be present on imaging studies prior to the development of functional abnormalities of the lung allograft. This review encompasses the evolution of CT findings in CLAD, with emphasis on the underlying pathogenesis and pathologic condition, to enhance understanding of imaging findings. The purpose of this article is to familiarize the radiologist with the initial and follow-up CT findings of the obstructive, restrictive, and mixed forms of CLAD, for which early diagnosis and treatment may result in improved survival. Supplemental material is available for this article. © RSNA, 2021.

Emerging biomarkers in chronic lung allograft dysfunction

Introduction: Lung transplantation remains an important treatment for patients with end stage lung disease. Chronic lung allograft dysfunction (CLAD) remains the greatest limiting factor for long term survival. As the diagnosis of CLAD is based on pulmonary function tests, significant lung injury is required before a diagnosis is feasible, likely when irreversible damage has already occurred. Therefore, research is ongoing for early CLAD recognition, with biomarkers making up a substantial amount of this research.Areas covered: The purpose of this review is to describe available biomarkers, focusing on those which aid in predicting CLAD and distinguishing between different CLAD phenotypes. We describe biomarkers presenting in bronchial alveolar lavage (BAL) as well as circulating in peripheral blood, both of which offer an appealing alternative to lung biopsy.Expert opinion: Development of CLAD involves complex, multiple immune and nonimmune mechanisms. Therefore, evaluation of potential CLAD biomarkers serves a dual purpose: clinically, the goal remains early detection and identification of patients at increased risk. Simultaneously, biomarkers offer insight into the different mechanisms involved in the pathophysiology of CLAD, leading to the development of possible interventions. The ultimate goal is the development of both preventive and early intervention strategies for CLAD to improve the overall survival of our lung transplant recipients.

Update in Chronic Lung Allograft Dysfunction

Chronic lung allograft dysfunction (CLAD) is the major limitation to posttransplant survival. This review highlights the evolving definition of CLAD, risk factors, treatment, and expected outcomes after the development of CLAD.

Diagnostic value of plasma and bronchoalveolar lavage samples in acute lung allograft rejection: differential cytology

Diagnosis of acute lung allograft rejection is currently based on transbronchial lung biopsies. Additional methods to detect acute allograft dysfunction derived from plasma and bronchoalveolar lavage samples might facilitate diagnosis and ultimately improve allograft survival. This review article gives an overview of the cell profiles of bronchoalveolar lavage and plasma samples during acute lung allograft rejection. The value of these cells and changes within the pattern of differential cytology to support the diagnosis of acute lung allograft rejection is discussed. Current findings on the topic are highlighted and trends for future research are identified.

T-lymphocyte subsets in lung transplant recipients: association between nadir CD4 T-cell count and viral infections after transplantation

BACKGROUND

Little is known about the kinetics of T-cell subsets in lung transplant recipients (LTR) and their association with the occurrence of opportunistic infections (OI).

OBJECTIVES

To analyze the kinetics of T-lymphocyte subsets in LTR and the association between nadir CD4 T-cell count and viral infections after transplantation.

STUDY DESIGN

Serial measurements of peripheral blood CD4 and CD8 T-cell counts obtained during the first year post-transplantation from 83 consecutive LTR and their correlation with both viral OI and community-acquired infections post-transplantation were retrospectively analyzed.

RESULTS

LTR with a nadir CD4 T-cell count <200 cells/μl had consistently lower CD4 and CD8 T-cell counts than LTR with a nadir CD4 T-cell count >200 cells/μl (p<0.001). In LTR with a nadir CD4 T-cell count <200 cells/μl, the cumulative incidence of viral infections detected in peripheral blood and in bronchoalveolar lavage (BAL) samples was higher than in LTR with a nadir CD4 T-cell count >200 cells/μl (p=0.0012 and p=0.0058, respectively). A nadir CD4 T-cell count <200 cells/μl within the first three months post-transplantation predicted a higher frequency of viral infectious episodes in BAL samples within the subsequent six month period (p=0.0066).

CONCLUSIONS

Stratification of patients according to nadir CD4 T-cell count may represent a new and simple approach for early identification of patients at risk for subsequent virus infections.

Bronchoalveolar lavage as a tool to predict, diagnose and understand bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS), a condition of irreversible small airway fibrosis, is the principal factor limiting long-term survival after lung transplantation. Bronchoscopy and bronchoalveolar lavage (BAL), techniques central to lung transplant clinical practice, provide a unique opportunity to interrogate the lung allograft during BOS development and identify potential disease mechanisms or biomarkers. Over the past 20 years, numerous studies have evaluated the BAL cellular composition, cytokine profiles and protein constituents in lung transplant recipients with BOS. To date, however, no summative evaluation of this literature has been reported. We developed and applied objective criteria to qualitatively rank the strength of associations between BAL parameters and BOS in order to provide a comprehensive and systematic assessment of the literature. Our analysis indicates that several BAL parameters, including neutrophil count, interleukin-8, alpha defensins and MMP-9, demonstrate highly replicable associations with BOS. Additionally, we suggest that considerable opportunity exists to increase the knowledge gained from BAL analyses in BOS through increased sample sizes, covariant adjustment and standardization of the BAL technique. Further efforts to leverage analysis of BAL constituents in BOS may offer great potential to provide additional in-depth and mechanistic insights into the pathogenesis of this complex disease.

Pulmonary immune changes early after laparoscopic antireflux surgery in lung transplant patients with gastroesophageal reflux disease

BACKGROUND

The biologic mechanisms by which laparoscopic antireflux surgery (LARS) might influence the inflammatory process leading to bronchiolitis obliterans syndrome are unknown. We hypothesized that LARS alters the pulmonary immune profile in lung transplant patients with gastroesophageal reflux disease.

METHODS

In 8 lung transplant patients with gastroesophageal reflux disease, we quantified and compared the pulmonary leukocyte differential and the concentration of inflammatory mediators in the bronchoalveolar lavage fluid (BALF) 4 weeks before LARS, 4 weeks after LARS, and 12 months after lung transplantation. Freedom from bronchiolitis obliterans syndrome (graded 1-3 according to the International Society of Heart and Lung Transplantation guidelines), forced expiratory volume in 1 second trends, and survival were also examined.

RESULTS

At 4 weeks after LARS, the percentages of neutrophils and lymphocytes in the BALF were reduced (from 6.6% to 2.8%, P = 0.049, and from 10.4% to 2.4%, P = 0.163, respectively). The percentage of macrophages increased (from 74.8% to 94.6%, P = 0.077). Finally, the BALF concentration of myeloperoxide and interleukin-1β tended to decrease (from 2109 to 1033 U/mg, P = 0.063, and from 4.1 to 0 pg/mg protein, P = 0.031, respectively), and the concentrations of interleukin-13 and interferon-γ tended to increase (from 7.6 to 30.4 pg/mg protein, P = 0.078 and from 0 to 159.5 pg/mg protein, P = 0.031, respectively). These trends were typically similar at 12 months after transplantation. At a mean follow-up of 19.7 months, the survival rate was 75% and the freedom from bronchiolitis obliterans syndrome was 75%. Overall, the forced expiratory volume in 1 second remained stable during the first year after transplantation.

CONCLUSIONS

Our preliminary study has demonstrated that LARS can restore the physiologic balance of pulmonary leukocyte populations and that the BALF concentration of pro-inflammatory mediators is altered early after LARS. These results suggest that LARS could modulate the pulmonary inflammatory milieu in lung transplant patients with gastroesophageal reflux disease.

Respiratory Tract and Mediastinum

Normal cytology, abnormal and atypical cells, non-cellular components, and infectious cell changes are largely described together with benign, malignant, and neuroendocrine lesions regarding exfoliative and aspiration cytology of the lung. A separate section broadly addresses diagnostic findings and differential diagnoses in bronchoalveolar washings.

The section ‘Fine needle aspiration biopsy of mediastinal disorders’ covers in particular biopsy techniques, accuracy of liquid-based cytology, and the complex lesions of the thymus gland. Cytodiagnostic algorithms of the major benign and malignant pulmonary and mediastinal lesions and their respective differential diagnoses are additionally presented in synoptic setups.

Usefulness of exhaled nitric oxide to guide risk stratification for bronchiolitis obliterans syndrome after lung transplantation

The aim of this study was to assess fractional exhaled nitric oxide (FeNO) for the early diagnosis of bronchiolitis obliterans syndrome (BOS) after lung transplantation (LTX). 611 FeNO measurements in 166 consecutive patients were classified depending on BOS stage at the time of assessment and course during minimum follow-up of 3 months: (1) stable non-BOS, (2) unstable non-BOS, (3) stable BOS and (4) unstable BOS. Unstable course was defined as new onset of BOS≥1 or progression of BOS. FeNO before unstable course was significantly increased in comparison to their stable counterparts (non-BOS: 28.9 ± 1.2 ppb, n = 40 vs. 16.4 ± 0.8 ppb, n = 131 and BOS: 32.5 ± 1.3 ppb, n = 35 vs. 15.3 ± 0.8 ppb, n = 26; p = 0.01 each). Average time from FeNO reading to onset of deterioration was 117 ± 9 days in non-BOS and 136 ± 9 days in BOS patients. The positive and negative predictive value of FeNO >20 ppb for BOS was 69.0% and 96.9%, respectively. Serial measurements demonstrated significantly lower mean individual variation in stable recipients as compared to stable patients switching to unstable course (3.2 ± 0.3 ppb vs. 12.7 ± 1.4 ppb, p = 0.02). In particular, the excellent negative predictive value of persistently low FeNO readings for future BOS make FeNO assessments a useful tool for continuous risk stratification after LTX.

Cell profile of BAL fluid in children and adolescents with and without lung disease

The objective of this study was to review the literature on bronchoalveolar lavage fluid cell profiles in healthy children and adolescents, as well as on the use of BAL as a diagnostic and follow-up tool for lung disease patients in this age bracket. To that end, we used the Medline database, compiling studies published between 1989 and 2009 employing the following MeSH descriptors (with Boolean operators) as search terms: bronchoalveolar lavage AND cytology OR cell AND child. In healthy children, the cell profile includes alveolar macrophages (> 80%), lymphocytes (approximately 10%), neutrophils (approximately 2%) and eosinophils (< 1%). The profile varies depending on the disease under study. The number of neutrophils is greater in wheezing children, especially in non-atopic children, as well as in those with pulmonary infectious and inflammatory profiles, including cystic fibrosis and interstitial lung disease. Eosinophil counts are elevated in children/adolescents with asthma and can reach high levels in those with allergic bronchopulmonary aspergillosis or eosinophilic syndromes. In a heterogeneous group of diseases, the number of lymphocytes can increase. Evaluation of the BAL fluid cell profile, when used in conjunction with clinical and imaging findings, has proven to be an essential tool in the investigation of various lung diseases. Less invasive than transbronchial and open lung biopsies, BAL has great clinical value. Further studies adopting standard international protocols should be carried out. Such studies should involve various age groups and settings in order to obtain reference values for BAL fluid cell profiles, which are necessary for a more accurate interpretation of findings in children and adolescents with lung diseases.

Surgical correction of gastroesophageal reflux in lung transplant patients is associated with decreased effector CD8 cells in lung lavages: a case series

BACKGROUND

Lung transplantation is associated with a high incidence of gastroesophageal reflux disease (GERD). The presence of GERD is considered a risk factor for the subsequent development of obliterative bronchiolitis (OB), and surgical correction of GERD by gastric fundoplication (GF) may be associated with increased freedom from OB. The mechanisms underlying a protective effect from OB remain elusive. The objective of this study was to analyze the flow cytometric properties of BAL cells in patients who have undergone GF early after transplant.

METHODS

In a single-center lung transplant center, eight patients with GERD who were in the first transplant year underwent GF. Prior to and immediately following GF, BAL cells were analyzed by polychromatic flow cytometry. Spirometry was performed before and after GF.

RESULTS

GF was associated with a significant reduction in the frequency of BAL CD8 lymphocytes expressing the intracellular effector marker granzyme B, compared with the pre-GF levels. Twenty-six percent of CD8 cells were granzyme Bhi pre-GF compared with 12% of CD8 cells post-GF (range 8%-50% pre-GF, 2%-24% post-GF, P = .01). In contrast, GF was associated with a significant interval increase in the frequency of CD8 cells with an exhausted phenotype (granzyme Blo, CD127lo, PD1hi) from 12% of CD8 cells pre-GF to 24% post-GF (range 1.7%-24% pre-GF and 11%-47% post-GF, P = .05). No significant changes in spirometry were observed during the study interval.

CONCLUSIONS

Surgical correction of GF is associated with a decreased frequency of potentially injurious effector CD8 cells in the BAL of lung transplant recipients.

Acute rejection and humoral sensitization in lung transplant recipients

Despite the recent introduction of many improved immunosuppressive agents for use in transplantation, acute rejection affects up to 55% of lung transplant recipients within the first year after transplant. Acute lung allograft rejection is defined as perivascular or peribronchiolar mononuclear inflammation. Although histopathologic signs of rejection often resolve with treatment, the frequency and severity of acute rejections represent the most important risk factor for the subsequent development of bronchiolitis obliterans syndrome (BOS), a condition of progressive airflow obstruction that limits survival to only 50% at 5 years after lung transplantation. Recent evidence demonstrates that peribronchiolar mononuclear inflammation (also known as lymphocytic bronchiolitis) or even a single episode of minimal perivascular inflammation significantly increase the risk for BOS. We comprehensively review the clinical presentation, diagnosis, histopathologic features, and mechanisms of acute cellular lung rejection. In addition, we consider emerging evidence that humoral rejection occurs in lung transplantation, characterized by local complement activation or the presence of antibody to donor human leukocyte antigens (HLA). We discuss in detail methods for HLA antibody detection as well as the clinical relevance, the mechanisms, and the pathologic hallmarks of humoral injury. Treatment options for cellular rejection include high-dose methylprednisolone, antithymocyte globulin, or alemtuzumab. Treatment options for humoral rejection include intravenous immunoglobulin, plasmapheresis, or rituximab. A greater mechanistic understanding of cellular and humoral forms of rejection and their role in the pathogenesis of BOS is critical in developing therapies that extend long-term survival after lung transplantation.

Lung

Experiments with animals in the 1940 and 1950s demonstrated that lung transplantation was technically possible [33]. In 1963, Dr. James Hardy performed the first human lung transplantation. The recipient survived 18 days, ultimately succumbing to renal failure and malnutrition [58]. From 1963 through 1978, multiple attempts at lung transplantation failed because of rejection and complications at the bronchial anastomosis. In the 1980s, improvements in immunosuppression, especially the introduction of cyclosporin A, and enhanced surgical techniques led to renewed interest in organ transplantation. In 1981, a 45-year-old-woman received the first successful heart–lung transplantation for idiopathic pulmonary arterial hypertension (IPAH) [106]. She survived 5 years after the procedure. Two years later the first successful single lung transplantation for idiopathic pulmonary fibrosis (IPF) [128] was reported, and in 1986 the first double lung transplantation for emphysema [25] was performed.

Bronchoalveolar immunologic profile of acute human lung transplant allograft rejection

Bronchoalveolar lavage fluid (BALF) offers a potential means to diagnose acute rejection and could provide insight into the immune mechanisms responsible for lung allograft rejection. Transbronchial biopsies from 29 bronchoscopic procedures were assessed for rejection. Concurrent BALF lymphocyte subsets were examined by flow cytometry, including CD4 and CD8 T cells and their activation status by CD38 expression, natural killer (NK), NK-like T (NT), B, regulatory T, and invariant receptor NK-T cells. Percentages of CD4 were reduced, and CD8 and activation of CD4 T cells correlated with rejection. There were trends for increased NT, reduced NK, and increased B cell percentages with rejection, suggesting potential roles of these cells. Among regulatory cells, the percentages of regulatory T cells decreased and CD4/CD8 invariant NK-T cells increased during rejection, suggesting a proinflammatory profile. A unique BALF lymphocyte profile was associated with rejection and may provide insight into the pathogenesis of allograft rejection.

Acute lung transplant rejection is associated with localized increase in T-cell IFNgamma and TNFalpha proinflammatory cytokines in the airways

BACKGROUND

Allograft rejection remains a major cause of morbidity and mortality after lung transplantation and is associated with increased gene expression for proinflammatory cytokines. T cells are a major cell type involved in graft rejection. There have been no previous studies of cytokine production by T cells from blood, bronchoalveolar lavage (BAL), and intraepithelial T cells from bronchial brushings (BB) during rejection episodes; we hypothesized that T-cell proinflammatory cytokines would be increased in the airways during rejection episodes despite standard immunosuppression regimens.

METHOD

To investigate changes in cytokine profiles during rejection episodes, whole blood, BAL, and BB from stable lung transplant patients and those with acute rejection were stimulated in vitro and intracellular cytokine production by CD8- (CD4+) and CD8+ T-cell subsets determined using multiparameter flow cytometry.

RESULTS

Transforming growth factor (TGF)-beta was significantly decreased in blood CD4+ and CD8+ T cells while interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha were significantly increased in BAL CD4+ and CD8+ T cells in patients with evidence of rejection. There was no change in CD4:CD8, interleukin (IL)-2, or IL-4 between stable and rejecting groups.

CONCLUSIONS

Acute lung transplant rejection is associated with decreased intracellular T-cell TGFbeta in blood and increased intracellular IFNgamma and TNFalpha in BAL CD4+ and CD8+ T cells. Drugs that effectively reduce airway T-cell IFNgamma and TNFalpha proinflammatory cytokine production may improve current protocols for reducing acute graft rejection in lung transplant patients.

Characterization of the innate immune response to chronic aspiration in a novel rodent model

Background

Although chronic aspiration has been associated with several pulmonary diseases, the inflammatory response has not been characterized. A novel rodent model of chronic aspiration was therefore developed in order to investigate the resulting innate immune response in the lung.

Methods

Gastric fluid or normal saline was instilled into the left lung of rats (n = 48) weekly for 4, 8, 12, or 16 weeks (n = 6 each group). Thereafter, bronchoalveolar lavage specimens were collected and cellular phenotypes and cytokine concentrations of IL-1alpha, IL-1beta, IL-2, IL-4, IL-6, IL-10, GM-CSF, IFN-gamma, TNF-alpha, and TGF-beta were determined.

Results

Following the administration of gastric fluid but not normal saline, histologic specimens exhibited prominent evidence of giant cells, fibrosis, lymphocytic bronchiolitis, and obliterative bronchiolitis. Bronchoalveolar lavage specimens from the left (treated) lungs exhibited consistently higher macrophages and T cells with an increased CD4:CD8 T cell ratio after treatment with gastric fluid compared to normal saline. The concentrations of IL-1alpha, IL-1beta, IL-2, TNF-alpha and TGF-beta were increased in bronchoalveolar lavage specimens following gastric fluid aspiration compared to normal saline.

Conclusion

This represents the first description of the pulmonary inflammatory response that results from chronic aspiration. Repetitive aspiration events can initiate an inflammatory response consisting of macrophages and T cells that is associated with increased TGF-beta, TNF-alpha, IL-1alpha, IL-1beta, IL-2 and fibrosis in the lung. Combined with the observation of gastric fluid-induced lymphocyitic bronchiolitis and obliterative bronchiolitis, these findings further support an association between chronic aspiration and pulmonary diseases, such as obliterative bronchiolitis, pulmonary fibrosis, and asthma.

Transient airway colonization is associated with airway inflammation after lung transplantation

Lower airway tract colonization may trigger neutrophil-mediated airway inflammation. We investigated whether transient airway colonization influences airway inflammation and pulmonary function after lung transplantation (LTx). In this retrospective study, stable LTx patients with consecutive broncho-alveolar lavages (BAL), the first colonized and the second noncolonized, were included to create a Pooled group (P, n=32) and a Gram Negative (GN, n=14), Gram Positive (GP, n=9) and Fungi (F, n=9) subgroup. Similarly, LTx patients with consecutive, noncolonized BAL samples were included as Control group (C, n=19). BAL analysis (cell counts, IL6, IL8) and forced expiratory volume (FEV(1)) were compared between groups. In the P group and the GN subgroup, colonized BAL samples showed a significant increase in total cells, neutrophilia and IL8-concentration and a significant decrease in FEV(1), even when compared with the matched samples of the C group. A significant increase in neutrophilia was observed in the GP subgroup, but no other significant difference was found either in the GP and F subgroup or the C group. IL6 levels were not significantly different between groups. Transient airway colonization, especially with Pseudomonas-like GN bacteria, in stable LTx patients may be associated with IL8-dependent neutrophilic airway inflammation and a, albeit subtle, decrease in FEV(1).

The pH of exhaled breath condensate of patients with allograft rejection after lung transplantation

Endogenous airway acidification, as assessed by the condensate pH, has been implicated in the pathophysiology of inflammatory airway diseases such as cystic fibrosis and asthma. The aim of this study was to investigate the pH of condensate in patients after lung transplantation (LTX). From the cohort of transplanted patients at our center, 83 patients (9 heart-lung transplantation, 48 double-lung transplantation, 26 single-lung transplantation) were recruited and analyzed in a cross-sectional manner: 26 patients were diagnosed with chronic rejection or bronchiolitis obliterans syndrome (BOS), 7 patients were diagnosed with acute rejection (AR) while 50 patients had no evidence of rejection according to the International Society for Heart and Lung Transplantation criteria. The condensate pH was significantly reduced in patients with BOS and AR when compared to patients without rejection and control subjects (5.8 +/- 0.5 and 6.2 +/- 0.4 versus 6.6 +/- 0.4 and 6.5 +/- 0 .4, respectively; p < 0.05). Moreover, there was a significant correlation between condensate pH levels and the BOS grade (r =-0.62; p < 0.01), the FEV(1) (r = 0.39; p < 0.01) and the total cell and neutrophil count in bronchoalveolar lavage fluid (r =-0.39 and r =-0.56, respectively; p < 0.01). Airway acidification occurs in BOS and may directly or indirectly reflect airway inflammation in patients with allograft rejection after LTX. Measuring condensate pH might thus be a new tool for the evaluation of rejection in lung transplant patients.

Analysis of chronic lung transplant rejection by MALDI-TOF profiles of bronchoalveolar lavage fluid

While lung transplant is an effective therapy for advanced lung disease, chronic allograph rejection remains a primary basis for lower survival rates than those for other solid organ transplants. This study used carefully controlled Zip-Tip extraction of bronchoalveolar lavage fluid (BALF) followed by MALDI-TOF MS to identify biomarkers of chronic lung transplant rejection. Many differences were observed between controls, those who did not develop chronic rejection within 100 months, and patients who had developed chronic rejection, diagnosed as bronchiolitis obliterans syndrome (BOS). Intensity ratios of peaks within the same MALDI-TOF profile were used to quantify the result. One of the best identifiers of BOS was a lowered ratio of clara cell protein (CCP m/z = 15,835) to lysozyme (m/z = 14,700), which gave 94% specificity and 74% sensitivity for diagnosis. Furthermore, low values for CCP/Lysozyme (<0.3) were observed in 66% of samples taken at 1 to 15 months prior to the diagnosis of BOS. Many other components of the profile gave similar or better outcomes for diagnosis but tended to be less valuable for the prediction of future disease. Overall, this study demonstrated the feasibility of this approach for the detection of disease biomarkers.

Increased intracellular pro- and anti-inflammatory cytokines in bronchoalveolar lavage T cells of stable lung transplant patients

BACKGROUND

Allograft rejection remains a major cause of morbidity and mortality following lung transplantation and is associated with an increased expression of T-cell proinflammatory cytokines. We have recently shown that peripheral blood T-cell proinflammatory cytokine production was significantly reduced in stable lung transplant patients consistent with immunosuppression therapy. However, analysis of inflammatory cytokine profiles in bronchoalveolar lavage (BAL) T cells may be more relevant than peripheral blood T cells for assessing graft status.

METHODS

To investigate the immunomodulatory effects of currently used immunosuppressive regimens on BAL T-cell cytokine production, whole blood and BAL from stable lung transplant patients and control volunteers was stimulated in vitro and cytokine production by CD8+ and CD4+ T-cell subsets determined using multiparameter flow cytometry.

RESULTS

There was a significant decrease in T-cell proinflammatory cytokine production in BAL compared with blood from control subjects but not transplant patients. Anti-inflammatory cytokine IL-4 was increased in BAL compared with blood from both groups. There was a significant increase in IFNgamma, IL-2, IL-4, TGFbeta, and TNFalpha production by CD8 T cells and IFNgamma and TNFalpha production by CD4 T cells in BAL from transplant patients compared with controls.

CONCLUSIONS

We have shown decreased T-cell pro- and anti-inflammatory cytokine production in BAL compared with blood in control subjects but not in stable lung transplant patients. Current immunosuppression protocols have limited effect on T-cell proinflammatory cytokine production in BAL but do upregulate anti-inflammatory cytokines IL-4 and TGFbeta. Drugs that effectively reduce T-cell proinflammatory cytokine production in BAL may improve current protocols for reducing graft rejection in these patients.

Longitudinal Comparisons of Lymphocytes and Subtypes between Airway Wall and Bronchoalveolar Lavage after Human Lung Transplantation

BACKGROUND

T lymphocytes are crucial in lung allorejection. The contribution of lymphocyte subtypes to the pathogenesis of chronic rejection (bronchiolitis obliterans syndrome [BOS]) remains unclear.

METHODS

Twenty-nine initially healthy lung transplant recipients underwent 136 bronchoscopic assessments, including bronchoalveolar lavage (BAL) (with flow cytometry) and endobronchial biopsies (EBB) (with immunohistochemistry) over 3 years of follow-up.

RESULTS

Of the 29 patients studied over 3 years, 23 developed BOS category 0 p and 17 went on to BOS 1. Compared with controls, the BAL percentage of CD4 cells was lower and the percentage of CD8 cells was increased significantly early posttransplant. Subsequent BAL lymphocyte subtype changes with time, or with the development of BOS, were minimal. By contrast, the early posttransplant EBB lymphocyte numbers were normal (P>0.05 vs. controls); subsequently, CD3 and CD8 (but not CD4) cells were increased with time in patients who did not develop BOS (P<0.05) and, more strikingly, in patients who eventually developed BOS (P<0.01). Multivariate analyses suggested an association between BAL lymphocytes (percentage) and azathioprine dose, female gender, rejection grade A on transbronchial biopsies, and pre-BOS status, whereas EBB CD8 cell counts were associated with time posttransplant, pretransplant diagnosis, and rejection grade B on TBB.

CONCLUSIONS

There is an early, persistent low percentage of BAL CD4 T cells, high BAL CD8 T cells, and progressively increasing airway wall CD3 and CD8 T cells with time posttransplant in healthy patients (but more predominantly in BOS patients) after transplantation. These immunopathologic changes may suggest that CD8 T cells could escape current immunosuppression and participate in chronic lung rejection.

Bronchoalveolar lavage fluid characteristics in acute and chronic lung transplant rejection

BACKGROUND

The detection of graft rejection by bronchoalveolar lavage remains controversial.

METHODS

To assess the value of bronchoalveolar lavage fluid in acute and chronic rejection after lung transplantation we analyzed bronchoalveolar lavage fluid cellular differential characteristics, lymphocyte sub-types and interleukin-6 (IL-6) and interleukin-8 (IL-8) cytokine levels in patients with exclusively either acute rejection (n = 37) or bronchiolitis obliterans (BO; n = 48). Both groups were compared with a control group of lung transplantation patients without rejection or infection, matched for the time the lavage was performed after lung transplantation.

RESULTS

The bronchiolitis obliterans group showed marked neutrophilia, high IL-8 and higher CD4(+)CD25(+) and CD8(+)CD45(+) bronchoalveolar lavage fluid levels when compared with their stable controls. When using a cut-off point of >3% neutrophils in the lavage, the sensitivity for BO is 87.0%, the specificity 77.6%. The sensitivity of IL-8 for BO when using a cut-off point of >71.4 pg/ml is 74.5%, the specificity 83.3%. Bronchoalveolar lavage fluid in acute rejection was characterized by marked lymphocytosis, but showed no difference when compared with stable controls in any of the lymphocyte sub-types studied. When using a cut-off point of <==1% lymphocytes in the lavage, the sensitivity for acute rejection (AR) is 40.4%, the specificity 95.6%. The marked neutrophilia, high IL-8 cytokine level and more activated lymphocyte population in bronchiolitis obliterans may indicate ongoing local allograft rejection.

CONCLUSIONS

In the present study we were not able to show any difference in lymphocyte sub-types when comparing acute rejection and control subjects. Cellular and soluble parameters in bronchoalveolar lavage fluid appear useful for diagnosing bronchiolitis obliterans.

Surrogate markers and risk factors for chronic lung allograft dysfunction

Obliterative bronchiolitis (OB) is the histologic correlate of chronic allograft dysfunction in pulmonary transplantation. The histologic diagnosis of OB is challenging, therefore a physiologic definition, bronchiolitis obliterans syndrome (BOS) based on pulmonary function tests has been used as a surrogate marker for OB for the last decade. BOS has proven to be the best available surrogate marker for OB and is predictive of the ultimate endpoints of graft and patient survival. Multiple other clinical markers have been reported and proposed as alternates for or complements to BOS grade, but all need further evaluation and validation in large, prospective clinical trials. Lastly, given the early occurrence and high incidence of chronic allograft dysfunction, the easily measurable endpoint of BOS grade, and our lack of understanding of ways to prevent or alter the course of BOS, lung transplant recipients represent an ideal population for clinical trials targeting prevention and treatment of chronic allograft dysfunction.

A rapid flow cytometric method for determining the cellular composition of bronchoalveolar lavage fluid cells in mouse models of asthma

Mouse models of allergic asthma are increasingly used to study the immunopathology of this complex disorder. The degree and type of airway inflammation is often studied by determination of differential cell counts on cytospins of bronchoalveolar lavage fluid (BALF) cells stained with May-Grünwald Giemsa, in which the separation of eosinophils (eos) from neutrophils (neutro) and of monocytes (mono) from activated T cells can be quite problematic. In this study, we compared differential cell counts based on morphological criteria on May-Grünwald Giemsa stained cytospins with a newly developed flow cytometric method. BAL fluid cells were identified based on forward and side scatter characteristics (FSC and SSC), autofluorescence of macrophages, and simultaneous one-step staining with antibodies for T cells (CD3-Cy-Chrome), B cells (B220-Cy-Chrome), eosinophils (CCR3-PE), and dendritic cells (DCs) (MHCII-FITC, CD11c-APC). The validity of this flow cytometric determination was tested by morphological analysis of flow-sorted cellular subsets. In an animal model of ovalbumin-induced asthma, this new method correlated very well with the differential counts based on cytospins. Flow cytometric determination of the cellular composition of BAL fluid in mouse models of asthma is a rapid and easy method that can replace differential cell counts based on morphology.

Association of humoral immunity and bronchiolitis obliterans syndrome

Animal studies have shown that blockade of complement may reduce the severity of and/or prevent the development of bronchiolitis obliterans syndrome (BOS), suggesting a role for complement activation. We explored the hypothesis that humoral immunity plays a role in the evolution of BOS. Thirteen unilateral lung transplant patients with BOS defined the patient population. Fresh frozen tissue was analyzed for deposition of C1q, C4d, C5b-9 and immunoglobulin (IgG, IgM, IgA). An indirect immunofluorescent assay was also conducted with patient serum against cytospins of the pulmonary endothelium. In each case the biopsies showed a microvascular injury syndrome involving the bronchial wall characterized by one or more of hemorrhage, fibrin deposition, and endothelial cell necrosis. Other features included bronchial epithelial and chondrocyte necrosis. The end-stage lesion was a thinned bronchial epithelial lining mural fibrosis. Immunofluorescent analysis showed deposition of C1q, C3, C4d, C5b-9, and immunoglobulin in the bronchial epithelium, chondrocytes, basement membrane zone of the bronchial epithelium, and bronchial wall microvasculature. The indirect antiendothelial cell antibody assay was positive in all tested. Humoral immunity may play a role in the pathogenesis of BOS; the antigenic targets include the bronchial wall microvasculature, bronchial epithelium, and chondrocytes.

Acute allograft rejection after lung transplantation: diagnosis and therapy

Acute rejection remains a significant problem after lung transplantation. While it generally is a treatable condition, significant resources and therapies are directed toward its prevention and resolution. Its larger significance undoubtedly rests in its contribution to the pathogenesis of BOS. Significant questions regarding the origins of AR, the role of LBB, alternative histologic appearances of acute allograft injury, and optimal therapy remain. Controversy regarding the utility of surveillance bronchoscopy and preemptive treatment of occult AR persists because of lack of conclusive evidence. Future investigations might resolve these matters and provide more efficacious and less toxic therapies that will hopefully reduce the impact of chronic rejection and improve long-term outcomes.

Critical care issues in lung and heart transplantation

Although much has been accomplished in HTx and LTx in the past few decades, much remains to be conquered. It is an ever-changing, always fascinating field. Though science and technology know no limits, the primary limitation of HTx and LTx continues to be the availability of donor organs. One can only hope that further advances in educating the public will help close the large gap between the list of those waiting and the organs available for transplantation.