Interstitial and airspace granulation tissue reactions in lung transplant recipients

Chronic Lung Allograft Dysfunction: Clinical Manifestations and Immunologic Mechanisms

The term "chronic lung allograft dysfunction" has emerged to describe the clinical syndrome of progressive, largely irreversible dysfunction of pulmonary allografts. This umbrella term comprises 2 major clinical phenotypes: bronchiolitis obliterans syndrome and restrictive allograft syndrome. Here, we discuss the clinical manifestations, diagnostic challenges, and potential therapeutic avenues to address this major barrier to improved long-term outcomes. In addition, we review the immunologic mechanisms thought to propagate each phenotype of chronic lung allograft dysfunction, discuss the various models used to study this process, describe potential therapeutic targets, and identify key unknowns that must be evaluated by future research strategies.

Esophageal Evaluation for Patients Undergoing Lung Transplant Evaluation: What Should We Do for Evaluation and Management

Lung transplantation is a high-risk, but lifesaving, procedure for patients with end-stage lung disease. Although 1-year survival is high, long-term survival is not nearly as high, due mainly to acute and chronic rejection. Bronchiolitis obliterans syndrome is the most common type of chronic rejection and often leads to poor outcomes. For this reason, esophageal testing in the lung transplant population has become a major issue, and this article discusses the evidence behind esophageal testing, the importance of esophageal dysmotility gastroesophageal reflux disease, both acidic and nonacidic reflux, and aspiration and the treatment of these findings.

Up-to-date role of biologics in the management of respiratory syncytial virus

INTRODUCTION

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease in young children and a substantial contributor to respiratory tract disease throughout life. Despite RSV being a high priority for vaccine development, there is currently no safe and effective vaccine available. There are many challenges to developing an RSV vaccine and there are limited antiviral drugs or biologics available for the management of infection. In this article, we review the antiviral treatments, vaccination strategies along with alternative therapies for RSV.

AREAS COVERED

This review is a summary of the current antiviral and RSV vaccination approaches noting strategies and alternative therapies that may prevent or decrease the disease severity in RSV susceptible populations.

EXPERT OPINION

This review discusses anti-RSV strategies given that no safe and efficacious vaccines are available, and therapeutic treatments are limited. Various biologicals that target for RSV are considered for disease intervention, as it is likely that it may be necessary to develop separate vaccines or therapeutics for each at-risk population.

Bone Marrow-derived Mesenchymal Stem Cells and Chronic Allograft Disease in a Bronchiolitis Obliterans Animal Model

INTRODUCTION

Bronchiolitis obliterans (BO) is the most common expression of chronic allograft dysfunction in lung transplantation. Moreover, BO represents the major cause of death in the long-term after this procedure. On the other hand, mesenchymal stem cells have been tested in animal models of BO aiming to interfere in its development. The aim of this experimental study is to explore the role of bone-marrow derived stem cells (BMSCs) as a preventive intervention of BO occurrence.

MATERIALS AND METHODS

This an experimental randomized study. A bronchiolitis obliterans animal model in rats was reproduced: heterotopical tracheal transplant model in lung parenchyma. Five of these animals were used as control group. After setting up the model, individuals were divided in 3 groups of treatment (n=15), in which BMSCs were administered in 3 different time points after the tracheal transplant (tracheal transplantation and BMSCs administration occurred the same day, group G0; after 7 days, group G7; after 14 days, group G14. In addition, within each group, BMSCs were administered through 3 different routes: endotracheally, endovascular and topically in the lung parenchyma). Animals were sacrificed at 21 days. Histology, fluorescence in situ hybridization and immunohistochemistry techniques were performed for identifying stem cells.

RESULTS

Compared to control group, animals receiving BMSCs showed large neovessels in a loose fibrous matrix. Group G7 showed less fibrosis (p<0.033) and edema (p<0.028). Moreover, G7 animals receiving stem cells endotracheally showed no fibrosis (p<0.008). Alveolar-like patches of tissue were observed among all groups (53.4%, 46.7% and 40% in G0, G7 and G14 respectively), consisting of cells expressing both stem and alveolar cells biomarkers.

CONCLUSION

BMSCs modify the course of bronchiolitis obliterans and differentiate into alveolar cells. Endotracheal administration of BMSCs 7 days after the heterotopical tracheal transplant might be considered an effective way to prevent BO in this animal model.

Organizing pneumonia secondary to Pneumocystis jirovecii infection in a kidney transplant recipient: Case report and review of literature

Organizing pneumonia (OP), previously known as bronchiolitis obliterans OP, is a diffuse parenchymal lung disease affecting the distal bronchioles, alveolar ducts, and alveolar walls. Pulmonary infections, especially bacterial and viral diseases, are known to be associated with the secondary form of OP. OP secondary to fungal infections is less common. Here, we report a case of OP associated with pneumocystis pneumonia (PCP) in a kidney transplant recipient on tacrolimus-based triple immunosuppression. The index case had developed new lung consolidation toward the end of trimethoprim-sulfamethoxazole therapy for PCP. Spontaneous clinical and radiographic resolution was seen without any increment in the dose of corticosteroids. We review the literature and present a summary of all reported cases of OP associated with PCP to date.

Combined diffusing capacity for nitric oxide and carbon monoxide as predictor of bronchiolitis obliterans syndrome following lung transplantation

BACKGROUND

There is a need for non-invasive parameters that are sensitive to the development of the bronchiolitis obliterans syndrome (BOS) in lung transplantation (LTx) patients. We studied whether the pulmonary diffusing capacity for inhaled nitric oxide is capable of detecting BOS stages.

METHODS

Sixty-one LTx patients were included into this cross-sectional study (19/29/7/3/3 in BOS stages 0/0-p/1/2/3). For analysis stages 0/0-p versus 1/2/3 ("BOS binary-early"), and stages 0/0-p/1 versus 2/3 ("BOS binary-late") were summarized. Measurements of the combined diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO) were compared with spirometry and bodyplethysmography, and their relative importance was evaluated by discriminant analysis.

RESULTS

Regarding the recognition of "BOS binary-early", among spirometric parameters forced expiratory volume in 1 s (FEV1) was best, among bodyplethysmographic parameters airway resistance, and among diffusing parameters DLNO. Regarding "BOS binary-late", DLNO was inferior to bodyplethysmographic parameters.

CONCLUSION

Although the study comprised only measurements at a single time point and no follow-up, DLNO outperformed FEV1, the time course of which is used in detecting BOS. Together with its pathophysiological plausibility, this result suggests that the measurement of DLNO, possibly over time, could be an easily applicable tool for the monitoring of LTx patients and should be evaluated in larger studies.

Azithromycin Fails to Prevent Accelerated Airway Obliteration in T-bet-/- Mouse Lung Allograft Recipients

BACKGROUND

Cellular and molecular mechanisms of acute and chronic lung allograft rejection have yet to be clearly defined, and obliterative bronchiolitis (OB) remains the primary limitation to survival in lung transplant recipients (LTRs). We have previously shown that T-bet-deficient recipients of full major histocompatibility complex (MHC)-mismatched, orthotopic left lung transplants develop accelerated obliterative airway disease (OAD) in the setting of acute cellular rejection characterized by robust alloimmune CD8⁺ interleukin (IL)-17 and interferon (IFN)-γ responses that are attenuated with neutralization of IL-17. Azithromycin has been shown to be beneficial in some LTRs with bronchiolitis obliterans syndrome/OB. Here, we evaluated the effects of azithromycin on rejection pathology and T-cell effector responses in T-bet^-/- recipients of lung transplants.

METHODS

Orthotopic left lung transplantation was performed in BALB/c → B6 wild type or BALB/c → B6 T-bet^-/- strain combinations as previously described. Mice treated with azithromycin received 10 mg/kg or 50 mg/kg subcutaneously daily. Lung allograft histopathology was analyzed at day 10 or day 21 post-transplantation, and neutrophil staining for quantification was performed using anti-myeloperoxidase. Allograft mononuclear cells were isolated at day 10 for T-cell effector cytokine response assessment using flow cytometry.

RESULTS

We show that while azithromycin significantly decreases lung allograft neutrophilia and CXCL1 levels and attenuates allospecific CD8⁺ IL-17 responses early post-transplantation, OAD persists in T-bet-deficient mice.

CONCLUSIONS

Our results indicate that lung allograft neutrophilia is not essential for the development of OAD in this model and suggest allospecific T-cell responses that remain despite marked attenuation of CD8⁺ IL-17 are sufficient for obliterative airway inflammation and fibrosis.

Critical Care Aspects of Lung Transplant Patients

Major strides have been made in lung transplantation during the 1990s and it has become an established treatment option for patients with advanced lung disease. Due to improvements in organ preservation, surgical techniques, postoperative intensive care, and immunosuppression, the risk of perioperative and early mortality (less than 3 months after transplantation) has declined [1]. The transplant recipient now has a greater chance of realizing the benefits of the long and arduous waiting period.

Despite these improvements, suboptimal long-term outcomes continue to be shaped by issues such as opportunistic infections and chronic rejection. Because of the wider use of lung transplantation and the longer life span of recipients, intensivists and ancillary intensive care unit (ICU) staff should be well versed with the care of lung transplant recipients.

In this clinical review, issues related to organ donation will be briefly mentioned. The remaining focus will be on the critical care aspects of lung transplant recipients in the posttransplant period, particularly ICU management of frequently encountered conditions. First, the groups of patients undergoing transplantation and the types of procedures performed will be outlined. Specific issues directly related to the allograft, including early graft dysfunction from ischemia-reperfusion injury, airway anastomotic complications, and infections in the setting of immunosuppression will be emphasized. Finally nonpulmonary aspects of posttransplant care and key pharmacologic points in the ICU will be covered.

ALN-RSV01 for prevention of bronchiolitis obliterans syndrome after respiratory syncytial virus infection in lung transplant recipients

BACKGROUND

Respiratory syncytial virus (RSV) infection in lung transplant (LTx) patients is associated with an increased incidence of bronchiolitis obliterans syndrome (BOS). ALN-RSV01 is a small interfering RNA targeting RSV replication that was shown in an earlier Phase 2a trial to be safe and to reduce the incidence of BOS when compared with placebo.

METHODS

We performed a Phase 2b randomized, double-blind, placebo-controlled trial in RSV-infected LTx patients to examine the impact of ALN-RSV01 on the incidence of new or progressive BOS. Subjects were randomized (1:1) to receive aerosolized ALN-RSV01 or placebo daily for 5 days.

RESULTS

Of 3,985 symptomatic patients screened, 218 were RSV-positive locally, of whom 87 were randomized to receive ALN-RSV01 or placebo (modified intention-to-treat [mITT] cohort). RSV infection was confirmed by central laboratory in 77 patients (ALN-RSV01, n = 44; placebo, n = 33), which comprised the primary analysis cohort (central mITT [mITTc]). ALN-RSV01 was found to be safe and well-tolerated. At Day 180, in ALN-RSV01-treated patients, compared with placebo, in the mITTc cohort there was a trend toward a decrease in new or progressive BOS (13.6% vs 30.3%, p = 0.058), which was significant in the per-protocol cohort (p = 0.025). Treatment effect was enhanced when ALN-RSV01 was started <5 days from symptom onset, and was observed even without ribavirin treatment. There was no significant impact on viral parameters or symptom scores.

CONCLUSIONS

These results confirm findings of the earlier Phase 2a trial and provide further support that ALN-RSV01 reduces the risk of BOS after RSV in LTx recipients.

Update on Bronchiolitis Obliterans Syndrome in Lung Transplantation

Lung transplantation has become an important therapeutic option for patients with end-stage organ dysfunction; however, its clinical usefulness has been limited by the relatively early onset of chronic allograft dysfunction and progressive clinical decline. Obliterative bronchiolitis is characterized histologically by luminal fibrosis of the respiratory bronchioles and clinically by bronchiolitis obliterans syndrome (BOS) which is defined by a measured decline in lung function based on forced expiratory volume (FEV₁). Since its earliest description, a number of risk factors have been associated with the development of BOS, including acute rejection, lymphocytic bronchiolitis, primary graft dysfunction, infection, donor specific antibodies, and gastroesophageal reflux disease. However, despite this broadened understanding, the pathogenesis underlying BOS remains poorly understood and once begun, there are relatively few treatment options to battle the progressive deterioration in lung function.

Expression of calcineurin activity after lung transplantation: a 2-year follow-up

The objective of this pharmacodynamic study was to longitudinally assess the activity of calcineurin during the first 2 years after lung transplantation. From March 2004 to October 2008, 107 patients were prospectively enrolled and their follow-up was performed until 2009. Calcineurin activity was measured in peripheral blood mononuclear cells. We report that calcineurin activity was linked to both acute and chronic rejection. An optimal activity for calcineurin with two thresholds was defined, and we found that the risk of rejection was higher when the enzyme activity was above the upper threshold of 102 pmol/mg/min or below the lower threshold of 12 pmol/mg/min. In addition, we report that the occurrence of malignancies and viral infections was significantly higher in patients displaying very low levels of calcineurin activity. Taken together, these findings suggest that the measurement of calcineurin activity may provide useful information for the management of the prevention therapy of patients receiving lung transplantation.

A review of bronchiolitis obliterans syndrome and therapeutic strategies

Lung transplantation is an important treatment option for patients with advanced lung disease. Survival rates for lung transplant recipients have improved; however, the major obstacle limiting better survival is bronchiolitis obliterans syndrome (BOS). In the last decade, survival after lung retransplantation has improved for transplant recipients with BOS. This manuscript reviews BOS along with the current therapeutic strategies, including recent outcomes for lung retransplantation.

Fibroblast phenotypes and their activity are changed in the wound healing process after lung transplantation

BACKGROUND

Lung transplantation (LTx) is established as a life-saving treatment in end-stage lung disease. However, long-term survival is hampered by the development of chronic rejection, almost synonymous with bronchiolitis obliterans syndrome (BOS). The rejection is characterized by deposition of extracellular matrix in small airways. Fibroblasts/myofibroblasts are the main producers of extracellular matrix molecules such as proteoglycans. This study compared fibroblast phenotype and activity in the wound healing process at different points after LTx in patients who later did, or did not, develop BOS.

METHODS

Distally derived fibroblasts from patients 6 and 12 months after LTx and from healthy controls were analyzed for production of the proteoglycans versican, perlecan, biglycan, and decorin, with and without transforming growth factor (TGF)-β(1). Fibroblast migration and proliferation were also studied.

RESULTS

At 6 and 12 months after LTx, versican production was higher in fibroblasts from LTx patients (p < 0.01 p < 0.01) than from controls. Fibroblasts from patients who later developed BOS were more responsive to TGF-β(1)-induced synthesis of versican and biglycan than patients without signs of rejection (p < 0.05). Production of perlecan and decorin was negatively correlated with fibroblast proliferation in fibroblasts at 6 months after LTx. In a more detailed case study of 2 patients, one with and one without BOS, the altered proteoglycan profile was associated with impaired lung function.

CONCLUSIONS

LTx changes the phenotype of fibroblasts to a non-proliferative but extracellular matrix-producing cell due to wound healing involving TGF-β(1). If not controlled, this may lead to development of BOS.

Organizing pneumonia as a manifestation of Pneumocystis jiroveci immune reconstitution syndrome in HIV-positive patients: report of 2 cases

Organizing pneumonia (OP) is a nonspecific response to various forms of lung injury. Although patients with human immunodeficiency virus (HIV) infection tend to develop several respiratory disorders, especially infections and malignances, the association of HIV infection and OP is unusual. Pneumocystis jiroveci infection is also rarely associated with OP. We describe the radiologic findings in 2 HIV-positive patients who shortly after introduction of highly active antiretroviral therapy, presented with clinical and radiologic deterioration, despite elevation of the CD4 cell count and viral load decrease. In both patients, clinical and radiologic features were consistent with OP and lung biopsy revealed OP associated with P. jiroveci infection. These findings are consistent with immune reconstitution syndrome due to P. jiroveci.

Revision of the 1996 working formulation for the standardization of nomenclature in the diagnosis of lung rejection

In 1990, an international grading scheme for the grading of pulmonary allograft rejection was adopted by the International Society for Heart and Lung Transplantation (ISHLT) and was modified in 1995 by an expanded group of pathologists. The original and revised classifications have served the lung transplant community well, facilitating communication between transplant centers with regard to both patient management and research. In 2006, under the direction of the ISHLT, a multi-disciplinary review of the biopsy grading system was undertaken to update the scheme, address inconsistencies of use, and consider the current knowledge of antibody-mediated rejection in the lung. This article summarizes the revised consensus classification of lung allograft rejection. In brief, acute rejection is based on perivascular and interstitial mononuclear infiltrates, Grade A0 (none), Grade A1 (minimal), Grade A2 (mild), Grade A3 (moderate) and Grade A4 (severe), as previously. The revised (R) categories of small airways inflammation, lymphocytic bronchiolitis, are as follows: Grade B0 (none), Grade B1R (low grade, 1996, B1 and B2), Grade B2R (high grade, 1996, B3 and B4) and BX (ungradeable). Chronic rejection, obliterative bronchiolitis (Grade C), is described as present (C1) or absent (C0), without reference to presence of inflammatory activity. Chronic vascular rejection is unchanged as Grade D. Recommendations are made for the evaluation of antibody-mediated rejection, recognizing that this is a controversial entity in the lung, less well developed and understood than in other solid-organ grafts, and with no consensus reached on diagnostic features. Differential diagnoses of acute rejection, airway inflammation and chronic rejection are described and technical considerations revisited. This consensus revision of the working formulation was approved by the ISHLT board of directors in April 2007.

A randomized trial of inhaled cyclosporine in lung-transplant recipients

BACKGROUND

Conventional regimens of immunosuppressive drugs often do not prevent chronic rejection after lung transplantation. Topical delivery of cyclosporine in addition to conventional systemic immunosuppression might help prevent acute and chronic rejection events.

METHODS

We conducted a single-center, randomized, double-blind, placebo-controlled trial of inhaled cyclosporine initiated within six weeks after transplantation and given in addition to systemic immunosuppression. A total of 58 patients were randomly assigned to inhale either 300 mg of aerosol cyclosporine (28 patients) or aerosol placebo (30 patients) three days a week for the first two years after transplantation. The primary end point was the rate of histologic acute rejection.

RESULTS

The rates of acute rejection of grade 2 or higher were similar in the cyclosporine and placebo groups: 0.44 episode (95 percent confidence interval, 0.31 to 0.62) vs. 0.46 episode (95 percent confidence interval, 0.33 to 0.64) per patient per year, respectively (P=0.87 by Poisson regression). Survival was improved with aerosolized cyclosporine, with 3 deaths among patients receiving cyclosporine and 14 deaths among patients receiving placebo (relative risk of death, 0.20; 95 percent confidence interval, 0.06 to 0.70; P=0.01). Chronic rejection-free survival also improved with cyclosporine, as determined by spirometric analysis (10 events in the cyclosporine group and 20 events in the placebo group; relative risk of chronic rejection, 0.38; 95 percent confidence interval, 0.18 to 0.82; P=0.01) and histologic analysis (6 vs. 19 events, respectively; relative risk, 0.27; 95 percent confidence interval, 0.11 to 0.67; P=0.005). The risks of nephrotoxic effects and opportunistic infection were similar for patients in the cyclosporine group and the placebo group.

CONCLUSIONS

Inhaled cyclosporine did not improve the rate of acute rejection, but it did improve survival and extend periods of chronic rejection-free survival. (ClinicalTrials.gov number, NCT00268515.).

Cytomegalovirus infection presenting as bronchial polyps in lung transplant recipients

BACKGROUND

Cytomegalovirus (CMV) is the most important opportunistic pathogen in lung transplant recipients and is associated with direct and indirect morbidity. Infection or disease with CMV is often diagnosed through detection of the virus in the blood, culture of bronchoalveolar lavage fluid, or histologic examination of lung tissue obtained on transbronchial biopsy. Endobronchial lesions involving the virus have received little attention, however.

METHODS

We reviewed the records of 76 endobronchial biopsies obtained at our institution from January 1999 through October 2004 and performed a detailed examination of the specimens and clinical histories for all patients with biopsy evidence of bronchial CMV infection.

RESULTS

We identified three patients with endobronchial CMV infection, manifested in each case as an endobronchial polyp. On histologic examination of the endobronchial biopsy specimens, cells with cytopathic effects characteristic or suggestive of CMV infection were present in two cases, and immunohistochemical staining confirmed the presence of CMV in all three. All patients were clinically well with normal chest X-rays before biopsy. Two of three patients had multiple subsequent episodes of CMV disease.

CONCLUSIONS

To our knowledge, this is the first report of endobronchial polypoid CMV disease in lung transplant recipients. Our results suggest that biopsy of endobronchial lesions in pulmonary allografts should be pursued to establish a definitive etiology.

Lung Transplantation Biopsy Specimens With Bronchiolitis Obliterans or Bronchiolitis Obliterans Organizing Pneumonia Due to Aspiration

Context.—Bronchiolitis obliterans (BO) is generally thought to be a marker of chronic airway rejection in patients who have undergone lung transplantation. Bronchoscopic biopsy specimens, by virtue of their small size, may sample only BO and not a lesion of bronchiolitis obliterans organizing pneumonia (BOOP). A role for ongoing chronic infection or aspiration has also been suggested, and the distinction of these etiologies may be difficult clinically and pathologically.

Objective.—To investigate the etiology of BO and BOOP in lung transplantation patients who had chronic aspiration.

Design.—This is a clinicopathologic study of 7 patients who had undergone lung transplantation in which biopsy findings suggested the possibility of chronic airway rejection but in which aspiration was subsequently proven as a cause of the bronchiolar disease.

Results.—All patients were men, who ranged in age from 19 to 57 years. A clinical diagnosis of aspiration was considered based on history, acid reflux testing, and radiographic findings in all 7 patients. Three patients had BO and 4 patients had BOOP. Histiocytic giant cells or foreign material was absent. The interval from transplantation to BO ascribed to aspiration ranged from 2.5 months to 7 years. The patients were treated aggressively with medication for gastroesophageal reflux disease. Their respiratory function and chest radiography results improved.

Conclusion.—Although BO may be a manifestation of rejection, it may also be a manifestation of aspiration. Because the latter is potentially correctable, aspiration should be considered etiologically in lung transplantation patients with either BO or BOOP. Reliable distinction between aspiration-related or rejection-related BO and BOOP cannot be made on morphologic grounds alone. Clinical and radiologic correlations are indicated to establish the distinction.

Bronchiolitis obliterans

PURPOSE OF REVIEW

Bronchiolitis obliterans (BO) occurs in both post-lung transplant and nontransplant-related individuals, and is characterized by mainly irreversible airflow obstruction that is often ultimately progressive.

RECENT FINDINGS

While post-lung transplant BO is a major cause of lung allograft dysfunction, and hence is better characterized than nontransplant-related BO, it is likely that many similarities in pathogenesis and treatment apply to both categories.

SUMMARY

Optimal management for BO remains to be established, and the role of retransplantation in this disease requires further consensus. Minimization of risk factors for BO and earlier detection in the form of methacholine challenge testing and HRCT scans of the chest amongst other forms of detection, may help in the stabilization and possible resolution of early BO.

Aspergillus and endobronchial abnormalities in lung transplant recipients

STUDY OBJECTIVE

To determine the relationship between aspergillus recovery from the airways of lung transplant recipients and the development of endobronchial abnormalities.

DESIGN

Retrospective case series.

SETTING

Tertiary-care hospital.

PATIENTS

All patients who underwent lung transplantation between December 1991 and June 1999.

MEASUREMENTS AND RESULTS

The study cohort included 38 patients. The primary end point was the bronchoscopic identification of an endobronchial abnormality. Aspergillus was isolated from the lungs of nine patients (23.7%). Most of these isolates occurred early after transplantation (mean, 8 weeks). Endobronchial abnormalities arose in seven of the patients (18.4%) and manifested as either exuberant granulation tissue or stricture formation. Six of the 9 (66.6%) patients with aspergillus developed airway lesions, compared to 1 of the 29 patients (3.4%) without aspergillus (p = 0.0002). Endobronchial abnormalities were 19.3 times more likely to occur in patients in whom aspergillus had previously been isolated. As a screening test for the subsequent diagnosis of an airway complication, the recovery of aspergillus had a sensitivity and specificity of 85.7% and 90.3%, respectively. These aspergillus-related endobronchial abnormalities were clinically relevant as evidenced by a mean increase of 25.9% in the FEV(1) after bronchoscopic intervention.

CONCLUSION

The early isolation of aspergillus from the airways of lung transplant recipients identifies patients at increased risk for the development of clinically significant endobronchial abnormalities.

Cell death in human lung transplantation: apoptosis induction in human lungs during ischemia and after transplantation

OBJECTIVE

To examine the presence and extent of apoptosis as well as the affected cell types in human lung tissue before, during, and after transplantation.

SUMMARY BACKGROUND DATA

Apoptosis has been described in various human and animal models of ischemia-reperfusion injury, including heart, liver, and kidney, but not in lungs. Therefore, the presence of apoptosis and its role in human lungs after transplantation is not clear.

METHODS

Lung tissue biopsies were obtained from 20 consecutive human lungs for transplantation after cold ischemic preservation (1-5 hours), after warm ischemia time (during implantation), and 30, 60, and 120 minutes after graft reperfusion. To detect and quantify apoptosis, fluorescent in situ end labeling of DNA fragments (TUNEL assay) was used. Electron microscopy was performed to verify the morphologic changes consistent with apoptosis and to identify the cell types, which were lost by apoptosis.

RESULTS

Almost no evidence of apoptosis was found in specimens after immediate cold and warm ischemic periods. Significant increases in the numbers of cells undergoing apoptosis were observed after graft reperfusion in a time-dependent manner. The mean fraction of apoptotic cells at 30, 60, and 120 minutes after graft reperfusion were 16.6%, 22.1%, and 34.9% of total cells, respectively. Most of the apoptotic cells appeared to be alveolar type II pneumocytes, as confirmed by electron microscopy.

CONCLUSIONS

Programmed cell death (apoptosis) appears to be a significant type of cell loss in human lungs after transplantation, and this may contribute to ischemia-reperfusion injury during the early phase of graft reperfusion. This cell loss might be responsible for severe organ dysfunction, which is seen in 20% of patients after lung transplantation. Therefore, this work is of importance to surgeons for the future development of interventions to prevent cell death in transplantation.

Constrictive (obliterative) bronchiolitis: diagnosis, etiology, and a critical review of the literature

Constrictive bronchiolitis (CB) (or obliterative bronchiolitis) designates inflammation and fibrosis occurring predominantly in the walls and contiguous tissues of membranous and respiratory bronchioles, with resultant narrowing of their lumens. It differs from bronchiolitis obliterans-organizing pneumonia in its histopathology and clinical course. Most cases of CB occur in the setting of organ transplants, particularly lung and heart-lung transplants, but also in bone marrow transplants. Other bona fide cases are rare: infection, particularly viral infection, appears to be a well-documented precursor to CB in children, but not in immunocompetent adults. Constrictive bronchiolitis also has been reported in the course of rheumatoid arthritis, in certain other autoimmune diseases such as pemphigus vulgaris, after inhalation of toxic gases such as nitrogen oxide, after ingestion of certain drugs or medicinal agents such as Sauropus androgynous, and as a cryptogenic illness. Recent reports suggest that CB, as defined by clinical criteria (that is, bronchiolitis obliterans syndrome), is very common in lung allograft recipients who survive more than 5 years and, although it is associated with significant mortality, it also can be clinically stable. Furthermore, with the current practice of close monitoring of these patients, it appears that CB may now be diagnosed at an earlier stage, at which resolution, or at least stabilization of progression, is possible. A histopathologic diagnosis of CB in lung transplant and other patients may be difficult to make due to the patchy distribution of lesions, the technical difficulty in obtaining tissue in late lesions with extensive fibrosis, and the failure to recognize lesions. With regard to the last of these, in early stages of disease, CB may be subtle and easily missed in routine hematoxylin-eosin-stained specimens, while in advanced stages the disease may be equally difficult to diagnose if the patchy scarring in the lung is interpreted as nonspecific. The relative loss of bronchioles and the relationship of the scars to contiguous arteries should signal the need for elastic stains to look for the residual elastica of the bronchioles amidst the foci of fibrosis. Increasingly, clinical grounds, including pulmonary functions studies and high-resolution computed tomography findings, are proving to be relatively sensitive methods of detecting CB. Finally, the progressive airway destruction in chronic transplantation rejection appears to be a T-cell-mediated process. The "active" form of constrictive bronchiolitis, with attendant lymphocytic inflammation of the airways, likely precedes the "inactive" or scarred form of constrictive bronchiolitis.

Bronchiolitis obliterans: pathogenesis, prevention, and management

Increasing early success-post lung transplant has been tempered by the long-term development of histologic bronchiolitis obliterans (OB) or of the progressive airway obstruction which is called bronchiolitis obliterans syndrome (BOS). Multiple lines of evidence suggest that OB/BOS is due to an injury directed against the epithelial cells in the airways of the donor lung by the immune system of the recipient. Acute rejection is the strongest risk factor for the subsequent development of this process. Efforts to prevent or minimize acute rejection may reduce the prevalence of OB/BOS. Results of treatment with augmented immunosuppression have been disappointing but the treatment of complicating infections in the allograft can be beneficial. Multicenter studies are needed to assess the efficacy of new immunosuppressive agents in preventing or treating OB/BOS.

Mixed (neutrophil-rich) interstitial pneumonitis in biopsy specimens of lung allografts: a clinicopathologic evaluation

STUDY OBJECTIVES

Mixed interstitial pneumonitis (MIP), defined herein as a diffuse neutrophil-rich inflammatory infiltrate within the interstitial tissues, is an uncommon finding that is not a standard manifestation of acute or chronic rejection. This study examines the clinical significance of MIP in lung allograft recipients at St. Louis University Hospital.

DESIGN

We retrospectively reviewed surgical pathology reports from a selected 50-month period, and identified MIP reported in 13 transbronchial biopsy specimens in lung transplant recipients, representing 4.7% of all lung allograft biopsy specimens seen during this 4-year period. Biopsy specimens with MIP were examined to confirm the presence of a neutrophil-rich interstitial infiltrate and other associated histopathologic findings. The culture results, cytopathologic findings, and clinical charts of the affected patients were also reviewed.

MEASUREMENTS AND RESULTS

The detection of MIP at some point in a patient's posttransplant course was found to be associated with a significantly shorter (p < 0.01) survival, when compared to lung allograft recipients who did not show this finding. A total of seven lung allograft recipients (23% of total) showed MIP at some point in their posttransplant course. Four of the seven (57%) were actively smoking following lung transplantation, compared to 0 of 22 patients who did not show MIP. Six of the 13 MIP biopsy specimens were associated with positive cultures. In no case did MIP coexist with the conventional histologic patterns of acute or chronic rejection. MIP also did not correlate with levels of immunosuppressive therapy or with the incidence of rejection at other times in the patients' posttransplant courses.

CONCLUSIONS

We found no evidence that MIP represents an unusual form of acute or chronic rejection. Instead, it appears to represent a response to acute injury, similar to other injury patterns (hyaline membranes, organizing pneumonia) in transplant recipients. Exposure to tobacco smoke is likely to have played a role in the development of MIP in at least some cases. Because patients with MIP had a significantly shorter posttransplant survival, MIP may usefully identify lung allograft recipients at risk for an adverse outcome.

Acute pulmonary allograft rejection. Mechanisms, diagnosis, and management

Rejection is a common complication following lung transplantation, and can lead to considerable short- and long-term morbidity. As numbers and survival rates of lung transplant recipients increase, it is apparent that acute rejection can occur months or years after transplantation, and may be resistant to standard therapies. Mechanisms of acute rejection have been well studied in other solid organ transplant recipients, and are beginning to be addressed in the lung recipient. This article addresses some of the common issues of diagnosis and management of acute rejection which arise frequently during the care of lung transplant recipients.

Bronchiolitis obliterans organizing pneumonia (BOOP) in lung transplant recipients

We reviewed all tissue specimens from 163 transplant patients (108 double lung transplant [DLT], 55 single lung transplant [SLT]) between November 1983 and January 1994 for abnormalities indicating bronchiolitis obliterans organizing pneumonia (BOOP) and found 17 cases (14 DLT and 3 SLT). Of the three SLTs, BOOP was diagnosed by open lung biopsy (OLB) in two and one was found at autopsy. Of the 14 DLTs, BOOP was diagnosed by transbronchial biopsy (TBB) specimens (9), OLB specimens (2), autopsy (1), TBB and OLB specimens (1), and OLB specimens and autopsy (1). BOOP was found between 1 and 43 months posttransplantation; time of survival from diagnosis was between 2 and 36 months with 9 patients presently alive. Concurrent pathologic diagnosis at the time of BOOP findings were as follows: acute rejection (7) (grade 1 [4] and grade 2 [3]), BO and grade 1 rejection (2), BO and grade 2 rejection (2), BO and Aspergillus infection (1), acute alveolar injury (1), acute alveolar injury and pulmonary embolus (1), acute rejection (grade 1) and Burkholderia cepacia pneumonia (1). No other pathologic diagnosis was found in 1 patient. In total, 11 of 17 patients (65%) had associated acute rejection. Of the 17 patients, 7 subsequently developed BO and 3 had BO before the finding of BOOP. Death occurred in 8 patients (5 DLT and the 3 SLT) between 2 and 6 months after the diagnosis. We conclude that BOOP is an important complication after lung transplantation; it was present in 13% of DLTs and 5% of SLTs. BOOP was most often associated with acute rejection.

Bronchiolitis obliterans organizing pneumonia-like reactions: a nonspecific response or an atypical form of rejection or infection in lung allograft recipients?

Bronchiolitis obliterans organizing pneumonia (BOOP) is a ubiquitous entity, known to occur either idiopathically or in association with various pulmonary disorders. Histologically, it is characterized by myxomatous connective tissue plugs present in the lumen of bronchioles with extension into the alveoli. Its significance in lung allograft recipients is not well documented. The authors reviewed all post-lung transplant biopsies (565 transbronchial; 19 open), explanted lungs for retransplantation (six), and autopsies (38) from 115 patients. A total of 32 patients (18 females and 14 males) showed histological evidence of BOOP-like reactions (ie, Masson bodies in 44 transbronchial and seven open lung biopsies). The mean age was 47 years (range = 14 to 69 years). Sixteen patients were recipients of single lungs, 14 received bilateral single lungs, and two had heart and double-lung transplants. BOOP-like reactions (BOOP-LRs) occurred as early as day 5 and as late as day 1,208 (40 months) posttransplantation. Twenty patients had one biopsy showing BOOP-LR, of which three patients had resolving mild acute rejection, four had ongoing minimal acute rejection, seven had ongoing mild acute rejection, one each had ongoing moderate and bronchiolar rejection, and four showed associated cytomegalovirus (CMV) pneumonitis. Seven patients had two biopsies each of BOOP-LR of which six were associated with ongoing minimal or mild acute rejection, and one had resolving mild acute rejection. Three patients had three biopsies each of BOOP-LR all associated with ongoing minimal or mild acute rejection. Two patients had four biopsies each, showing BOOP-LR, with ongoing mild or moderate acute rejection or CMV pneumonitis. Forty of the total 115 lung transplant patients (34.8%) have developed bronchiolitis obliterans syndrome (BOS) or chronic airway rejection. Twelve of these patients are from the study group, of which five have a biopsy proven histological diagnosis of obliterative bronchiolitis (OB), and the remaining seven patients have been diagnosed clinically by deteriorating lung function tests. The authors conclude that BOOP-LR in the lung transplant setting result from acute epithelial injury secondary to either allograft rejection or an ongoing infection and are not a component of, nor do they necessarily predispose to, chronic rejection.

Significance of clinically silent untreated mild acute cellular rejection in lung allograft recipients

Although acute rejection is a frequent occurrence after transplantation, the clinical behavior and pathological manifestations of untreated mild acute cellular rejection in clinically stable lung allograft recipients is poorly defined. Sixteen patients were identified who had asymptomatic mild acute rejection that was untreated but followed by subsequent pulmonary function tests and repeat transbronchial biopsy. Six patients had spontaneous resolution of their infiltrates; the condition of 10 patients worsened as observed from their biopsies or function studies. Those who worsened had more episodes of acute rejection per patient before the A2 biopsy (2.0 vs 1.3), and 50% developed bronchiolitis obliterans compared with 16% in the spontaneously regressing group. Pathological evaluation showed that patients with persistent or worsening untreated A2 rejection tended to have more large and small airway inflammation, larger numbers of eosinophils and plasma cells in their biopsies, and airway and airspace granulation tissue. These variables may be used to help determine which low grade lung rejection episodes should receive adjunctive immunosuppressive therapy.