Does histologic acute rejection in lung allografts predict the development of bronchiolitis obliterans?

HLA-A locus mismatches and development of antibodies to HLA after lung transplantation correlate with the development of bronchiolitis obliterans syndrome

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is the most common cause of morbidity and mortality after lung transplantation (LT). A retrospective analysis of clinical and immunologic variables were done to identify those that might predict the development of BOS.

METHODS

Of 112 LT performed over a 42-month interval, 94 survived at least 3 months and form the basis of this analysis. There was a minimum of 21 months follow-up. BOS was defined on the basis of declining spirometry (FEV1 <80% of baseline) and/or the presence of histologic obliterative bronchiolitis. All variables analyzed were subjected first to a univariate analysis; those variables appearing to carry significance were then subjected to a multivariate logistic regression analysis.

RESULTS

Univariate analysis revealed the following to be predictors of the development of BOS: age (the probability of developing BOS declined with advancing age); donor/recipient HLA-A locus mismatch, with actuarial freedom from BOS being significantly greater with no A-locus mismatches versus cases with one or two mismatches (P=0.031); and development of anti-HLA antibodies after transplantation (P=0.006 vs. recipients without detectable antibodies). In multivariate analysis, only HLA locus mismatch and development of anti-HLA antibodies were significant independent predictors of the development of BOS. The remaining clinical variables (gender, type of LT, indication for LT, graft ischemic time, use of cardiopulmonary bypass, cytomegalovirus) and immunologic variables (crossmatch, frequent early acute rejection) did not correlate with the development of BOS.

CONCLUSIONS

These data suggest that BOS is the result of an immune process, that differences at the HLA-A locus may play an important role in this process, and antibody-mediated injury may play a role in BOS.

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.

Increased gelatinolytic activity in bronchoalveolar lavage fluid in stable lung transplant recipients

Proteolytic enzymes have been proposed to play a role in the pathogenesis of various inflammatory pulmonary diseases accompanied by parenchymal remodeling. To assess the role of inflammatory cells and proteolytic enzymes in the development of chronic allograft rejection after lung transplantation, bronchoalveolar lavage fluid (BALF) samples from clinically stable lung transplant (LT) recipients (i.e., without evidence of active infection or rejection), heart transplant (HT) recipients, and healthy volunteers (NL) were analyzed for total white blood cell (WBC) count and differential cell count, along with gelatinolytic/type IV collagenolytic activity. The LT group displayed a significantly increased total WBC count, neutrophil count, and percent neutrophils compared with the NL group, confirming the presence of inflammation. Furthermore, gelatin zymography revealed a significant increase in activity of the 72 and 92 kD gelatinases in the LT group compared with the NL group. A positive correlation existed between neutrophil counts and the increase in proteolytic activity. Immunosuppressive therapy did not account for the findings, since no significant difference in cell counts or proteolytic activity existed between the NL and HT control groups. These findings, together with those of others that relate chronic lung allograft dysfunction to an increase in BALF neutrophils and collagen matrix remodeling, collectively indicate that up-regulated proteolytic activity may have a role in chronic rejection after lung transplantation.

Relation between polymerase chain reaction findings and morphological changes during cytomegalovirus infection in transplanted lung

Cytomegalovirus (CMV) can be present as a latent or productive infection resulting in disease. The polymerase chain reaction (PCR) is a sensitive technique to document the presence of CMV (DNA). Negative reactions are indicative of its absence. The presence of CMV (DNA) was assessed longitudinally in 261 transbronchial lung biopsy (TBB) specimens from 37 patients over a 6-month period. The TBB specimens from six serologically CMV-negative recipients who received lungs from serologically CMV-negative donors never showed a positive CMV-PCR(DNA) reaction during the study. Based on a study of their TBB specimens, 10 serologically CMV-positive recipients who received lungs from serologically CMV-negative donors all developed a CMV-PCR(DNA)-positive reaction and five (50%) morphologically manifested CMV disease. The remaining 21 serologically CMV-positive recipients who received lungs from serologically CMV-positive donors all developed a CMV-PCR(DNA)-positive reaction and 15 (71%) developed CMV pneumonitis. The data show that development of a positive CMV-PCR(DNA) reaction in a TBB sample within the first month after transplantation indicates a greatly increased risk of developing CMV disease. In addition, a positive CMV-PCR(DNA) reaction preceded morphologically manifest disease on average by 2 weeks. Comparisons between TBB and bronchoalveolar lavage show the former to provide a more dependable template.

Risk factors for the development of bronchiolitis obliterans syndrome after lung transplantation

OBJECTIVE

This study identifies specific clinical and immunologic factors in lung transplant recipients that influence the subsequent development of chronic allograft dysfunction.

METHODS

The study group consisted of 132 consecutive patients who received lung allografts (76 single, 25 bilateral single, and 31 heart-lung) and survived at least 90 days. One hundred twenty-one patients were used in the analysis that modeled time to development of histologic obliterative bronchiolitis or bronchiolitis obliterans syndrome.

RESULTS

Variables noted to have an effect on the time to development of bronchiolitis obliterans syndrome included cytomegalovirus pneumonitis (RR = 3.2, p = 0.001), late acute rejection (RR = 1.3, p = 0.02), human leukocyte antigen mismatches at the A loci (RR = 1.8, p = 0.02), total human leukocyte antigen mismatches (RR = 1.4, p = 0.04), and absence of donor antigen-specific hyporeactivity (52% vs 100% survival free from bronchiolitis obliterans syndrome at 2 years; p = 0.005). Cytomegalovirus pneumonitis had a significant effect on time to obliterative bronchiolitis (RR = 3.6, p = 0.0005), as did donor antigen-specific hyporeactivity (52% vs 100% survival free from obliterative bronchiolitis at 2 years; p = 0.01). In multivariate analysis, cytomegalovirus pneumonitis (RR = 3.2, p = 0.02), human leukocyte antigen mismatches at the A loci (RR = 2.4, p = 0.006), and late acute rejection (RR = 1.3, p = 0.02) were identified as predictors of bronchiolitis obliterans syndrome. Cytomegalovirus pneumonitis was associated with time to development of histologic obliterative bronchiolitis (RR = 2.3, p = 0.02).

CONCLUSIONS

Several risk factors were associated with the development of chronic allograft dysfunction, which, in turn, had a significant impact on long-term survival. Early identification of lung allograft recipients with risk factors for the development of bronchiolitis obliterans syndrome may allow modification in immunosuppression and antiviral therapy to potentially decrease the prevalence of this disorder.

Decreased expression of the cystic fibrosis transmembrane conductance regulator protein in remodeled airway epithelium from lung transplanted patients

The absence or mislocalization of cystic fibrosis transmembrane conductance regulator (CFTR) is regarded as being specific for cystic fibrosis (CF). In principle, the supply of a non-CF lung transplant to a CF patient should bring up normal CFTR expression in the lower airways. Immunolocalization of CFTR and of epithelial differentiation markers (ie, cytokeratins 13, 14, and 18, and desmoplakins 1 and 2) was carried out on 21 mucosal biopsies from the upper lobe of grafts in non-CF (n = 12) and CF patients (n = 9) retrieved between days 23 and 1,608 after lung transplantation. Biopsy specimens from seven non-CF and four CF patients presented either a pseudostratified respiratory epithelium or slight basal cell hyperplasia. CFTR was distributed at the apical membrane of the ciliated cells. In remodeled epithelia with basal cell hyperplasia or squamous metaplasia, CFTR was either weakly expressed in the cytoplasm of the superficial epithelial cells or was undetectable. The extent of epithelium remodeling was significantly correlated with an impairment of lung function. The results suggest that posttransplant airway epithelium dedifferentiation of the graft leads to the loss of properly targeted CFTR irrespective of the underlying disease of the recipient.

Lymphocytic airway infiltration as a precursor to fibrous obliteration in a rat model of bronchiolitis obliterans

BACKGROUND

Bronchiolitis obliterans is the most significant complication adversely affecting prolonged survival of lung allograft recipients. The evolution from the initial insult to the final pathologic entity is largely unknown. The aim of this study was to characterize the evolution of transplant-induced fibrous airway obliteration in a rat tracheal transplant model of bronchiolitis obliterans.

METHODS

Tracheal segments were transplanted from Brown Norway rats to Brown Norway rats (isografts) or to Lewis rats (allografts). Grafts were implanted into a subcutaneous pouch and an abdominal omental wrap. They were harvested at 14 different time points (from 1 day to 1 year after transplantation) and assessed histologically.

RESULTS

The fibrous airway obliteration developed only in allografts showing a triphasic time course: an initial ischemic phase (observed in both isografts and allografts) was followed by a marked lymphocytic infiltrative phase with complete epithelial loss (observed only in allografts, P<0.01), and finally by an obliterative phase with fibrous obliteration of the allograft airway lumen (P<0.01).

CONCLUSIONS

This animal model shows a distinct and reproducible triphasic time course in the development of obliterative airway lesions in allografts. It confirms that the mechanism leading to airway obliteration is immune mediated as only allografts showed this lesion and that lymphocytic infiltration is a precursor of the lesion in this model. The insights into the different phases demonstrated may lead to novel approaches regarding the type and timing of therapeutic interventions.

Obliterative bronchiolitis

Obliterative bronchiolitis following lung transplantation is common and potentially devastating. Its exact cause is undefined, but multiple immune and nonimmune processes contribute to its pathogenesis. Severe acute rejection and recurrent acute rejection have been shown to confer the greatest risk for obliterative bronchiolitis, signifying the central importance of alloimmunity in the disease process. Treatment of established disease with intensification of immune suppression has been of limited benefit, so current clinical strategies include early detection and minimization of risk. As our understanding of the disease evolves, it is hoped that effective interventions targeted at specific pathogenetic steps will emerge. In the meantime, obliterative bronchiolitis remains the most important and sinister long-term complication of lung transplantation.

Cyclosporine reduces development of obliterative bronchiolitis in a murine heterotopic airway model

Obliterative bronchiolitis (OB), an important threat to the long-term survival of lung transplant recipients, is characterized histologically by fibroproliferation within small airways. The pathogenesis of OB is thought to involve chronic allograft rejection, and therapy frequently includes augmentation of immunosuppression. We have developed a model that reproduces the pathologic lesion of OB and allows study of interventions designed to limit airway fibrosis. In this model, heterotopic transplantation of murine airways into immune-mismatched recipients results in epithelial abnormalities and fibroproliferation in the airway lumen, changes not seen in heterotopic isografts. Cyclosporine (CsA) inhibits activation and proliferation of T lymphocytes and is commonly administered after lung transplantation. We hypothesized that use of CsA in our model system would reduce fibroproliferation in tracheal allografts. To test this hypothesis, murine tracheas were transplanted heterotopically into allo matched and allomismatched recipients, and then treated with varying doses (5, 10, 15, or 25 mg/kg i.p. q.d.) of CsA. Controls included allografts and isografts not treated with CsA. After 30 days, tracheas were harvested and examined histologically. CsA markedly reduced the development of fibroproliferation in allografts (19% in treated allografts versus 90% in untreated allografts, P<0.0001), but did not reduce inflammation or airway epithelial cell injury. High-dose (25 mg/kg/day) CsA was more effective than lower doses in reducing fibroproliferation (0% in high dose versus 29% in low dose, P=0.04). These findings demonstrate that CsA significantly reduces development of the pathologic lesion of OB, and supports the role of alloimmunity in the pathogenesis of this disease.

Surveillance bronchoscopy in lung transplant recipients

STUDY OBJECTIVES

To establish whether a consensus exists among active transplant centers regarding the use and interpretation of information obtained by surveillance bronchoscopic lung biopsy (SBLB).

DESIGN

Prospective standardized questionnaire answered via mail and telephone communications.

PARTICIPANTS

A five page, 18-question survey was sent to all lung transplant programs listed by the United Network of Organ Sharing in North America, as well as eight selected international programs. Ninety-one surveys were sent to 83 North American and eight international programs. Seventy-four programs (81%) responded. Seventeen programs (19%) were excluded secondary to inactivity. The remaining 57 programs (63%) were included in final data analysis.

INTERVENTIONS

None.

RESULTS

Sixty-eight percent (39/57) of the responding programs perform SBLBs. Ninety-two percent of the programs performing SBLBs do so within the first month, and 69% continue to do so on a regular basis. Sixty-nine percent (27/39) of programs performing SBLBs continue to do so after 1 year. Eighty-six percent (32/37) of respondents believe that SBLB impacts on patient management at least 10% of the time. Technically, 90% (35/39) take biopsy specimens from more than one lobe per SBLB session. Fifty-nine percent (23/39) took 6 to 10 biopsy specimens per session, 33% (13/39) took three to five biopsy specimens, and 7% (4/39) took > 10 biopsy specimens per session. Eighty-six percent (32/37) of the responding centers reported treating asymptomatic rejection at grade 2A, while 14% (5/37) waited until histologic grade 3A before beginning treatment. Complications from SBLB were minimal with < 5% rates of pneumothorax, requirement for chest tube placements, or significant bleeding during SBLB reported by > 95% of the programs performing SBLB.

CONCLUSIONS

Most active lung transplant centers perform SBLBs and do so on a regular basis. However, a wide range of opinion exists over the utility and technique of SBLB and the impact of its results influencing outcome in the lung transplant recipient. To answer these questions, a randomized multicentered trial or registry to determine the effect of SBLB on lung transplant recipient morbidity and mortality is required.

Total lymphoid irradiation for refractory acute rejection in heart-lung and lung allografts

Persistent or recurrent acute allograft rejection (AR) refractory to high-dose steroid therapy can adversely affect long-term outcomes of heart-lung (HLT), bilateral-lung (BLT), and single-lung (SLT) transplantations. The use of total lymphoid irradiation (TLI) for the management of refractory acute AR in six transplant recipients (two men, four women; mean age, 29.8 +/- 3.8 years) is detailed. There are two HLT (primary pulmonary hypertension [PPH], cystic fibrosis [CF]), 1 BLT (pulmonary hypertension postventricular septal defect repair), and 3 SLT (sarcoid, PPH, congenital heart disease with atrial septal defect) recipients. Refractory AR is defined as persistent rejection unresponsive to high-dose steroid therapy in all cases. The BLT and SLT recipients had at least two moderate and one mild AR events per patient. The HLT recipients had at least two moderate acute heart and one severe and one mild asynchronous acute lung rejection events per patient. A total of 800 cGy of total lymphoid irradiation (TLI) was administered over a 5-week period. Mild and transient leukopenia was the only observed side effect. The patient with PPH received TLI 313 days after HLT for recurrent AR at another institution and died of ARDS 4 weeks after completing TLI. The patient with CF received TLI 707 days after HLT and died 457 days after TLI of severe obliterative bronchiolitis (OB) with multiorgan failure. The patient with BLT received TLI 176 days after transplant and died 372 days after TLI of respiratory failure related to severe rejection. One patient with SLT received TLI 78 days after transplant and died 679 days after TLI of severe acute AR. The two remaining patients with SLTs have been free from acute AR for more than 4 years. The patient with sarcoidosis received TLI 37 days after SLT following a clinical rejection event and two severe acute AR events. He is alive with normal lung function 5 years later. The patient with PPH received TLI 108 days after SLT following three moderate acute AR events and is alive with stable OB 4 years later. These limited preliminary results suggest that TLI has merit for the treatment of intractable acute AR following HLT and lung transplantation.

Enhancement of cytomegalovirus infection and acute rejection after allogeneic lung transplantation in the rat

A possible mechanism of the induction of lung transplant rejection by cytomegalovirus (CMV) infection is the inflammatory upregulation of adhesion ligand molecules on transplant endothelia by the viral infection leading to leukocyte activation. To study this question a rat model of rat cytomegalovirus (RCMV) infection and acute lung transplant rejection was established to study: (1) the influence of RCMV infection on the course of rejection, (2) the influence of rejection on the course of RCMV infection, and (3) the influence of RCMV on adhesion molecule expression and leukocyte infiltration. For this Lew (RT1l) rats received either syngenic (n=25) or allogeneic (BN, RT1n; n=38) left lateral lung transplants. Postoperatively, CsA 25mg/kg was given on days 1-3 and triple drug (CsA, Aza, Pred) immunosuppression was given from days 4-10 to induce systemic RCMV infection and acute rejection developed from postoperative day (POD) 15-25 in allogeneic transplants. In RCMV-positive animals the rejection grade was gradually increased at POD 15 and 18. Furthermore, after allogeneic transplantation an enhanced viral infection of the lung transplant as early as POD 11 was found and increased salivary gland PFU titers on days 20 and 25. In the absence of rejection infiltration a maximal induction of ICAM-1 adhesion molecules was found on lung endothelia in RCMV+ allogeneic animals as compared with noninfected controls. This induction was found to lesser degree for VCAM-1 and MHC class II adhesion ligand molecules. This was accompanied by a significantly increased CD11a+ and CD49d+ leukocyte infiltration into the alveolar interstitium on day 11 and 15 in infected transplants. The results show an enhancement of RCMV infection after allogeneic lung transplantation leading to endothelial activation and recruitment of CD11a/CD49d+ leukocytes. This mechanism may strongly influence transplant inflammation and the long-term course of lung transplant rejection.

Delayed development of obliterative bronchiolitis syndrome with OKT3 after unilateral lung transplantation. A plea for multicenter immunosuppressive trials

There is no consensus regarding the optimal induction immunosuppression regimen after lung transplantation (LT). In addition to the potential benefit of a reduced incidence of early acute allograft rejection, cytolytic induction immunosuppression may impact on long-term allograft function. We retrospectively assessed our incidence of obliterative bronchiolitis syndrome (OBS) stages Ia and IIa in LT survivors given two different cytolytic induction immunosuppression regimens: (between March 1989 and October 1990) OKT3 (5 mg/d)x10 to 14 days (n=11) vs (between November 1990 and April 1993) Minnesota antilymphocyte globulin (MALG) (10 to 15 mg/kgdx5 to 7 days. Cyclosporine (CSA) (whole blood polyclonal assay=600 to 800 ng/mL), azathioprine (1 to 2 mg/kg/d), and maintenance prednisone (0.2 mg/kg/d) were similar. Surveillance spirometry was performed monthly, in accordance with accepted American Thoracic Society criteria. Fiberoptic bronchoscopy with transbronchial biopsies (TBBs) were performed for clinical indications. Surveillance TBBs were not performed during the era of this study. As defined by the ISHLT "Working Formulation for the Standardization of Nomenclature and for Clinical Staging of Chronic Dysfunction in Lung Allografts," latencies to development of OBS stages Ia and IIa were determined by Kaplan-Meir analysis. Stepwise regression (Cox proportional hazards model) was performed for the variables: cytolytic induction regimen, episodes cytomegalovirus (CMV) pneumonitis, episodes CMV infection, serologic CMV donor (+): recipient (-) mismatch, prior pregnancy, HLA (A,B,DR +/- DQ) mismatches, episodes greater than grade A1 acute cellular rejection (ACR). We found that the OKT3 cohort experienced longer latencies for OBS stages Ia and IIa. Latencies to OBS stages Ia for OKT3 ve MALG were 962 +/- 65 vs 354 +/- 85 days (X +/- SEM) respectively. Brookmeyer-Crowley 95% confidence intervals for median latencies were 744 to 1,180 vs 266 to 510 days for OKT3 vs MALG, respectively. The Cox model was significant only for the variable of the induction cytolytic immunosuppression regimen (p=0.0015). By physiologic criteria, a longer course of OKT3 appeared superior to the short-course MALG protocol in delaying chronic lung allograft dysfunction. These effects may be related either to inherent differences in the antilymphocyte preparations or, alternatively, the difference in duration of treatment between groups. Surveillance TBB and treatment of detected occult ACR may serve to negate the observed differences in latencies for OBS.

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.

Development of bronchiolitis obliterans syndrome in recipients of heart-lung transplantation--early risk factors

Given the internationally recognized definition of bronchiolitis obliterans syndrome (BOS) and longer follow up of heart-lung transplant recipients, it is possible to establish some of the major risk factors for development and progression of BOS. Between April 1984 and 31 December 1993, 157 patients underwent heart-lung transplantation; 126 survived at least six months after operation and so were at risk of developing BOS. The following early risk factors were assessed for development of BOS grade 1 (21-35% decline in FEV1) and progression from grade 1 to grade 2 (36-50% decline in FEV1): age, gender and underlying diagnosis of the recipient, evidence of acute rejection and cytomegalovirus (CMV) infection within 6 months of operation, peak FEV1 achieved, age and gender of the donor, cold ischemic time of the graft, and matching of CMV serological status and HLA antigens of donor and recipient. The number of acute rejection episodes observed remained the single most important determinant of development of BOS grade 1 (relative risk 1.17 (1.06, 1.29), P=0.002) and progression to BOS grade 2 (relative risk 1.58 (1.02, 2.46), P=0.03). No other factors were significantly related to development or progression of BOS, although both evidence of CMV infection and disease and the number of HLA mismatches increased the risk. Bronchiolitis obliterans syndrome is a major problem for medium-to-long-term survivors of cardiothoracic transplantation. Acute rejection early after transplantation is a sensitive prognostic indicator of subsequent functional decline and requires prompt attention.

Cytolytic therapy for the treatment of bronchiolitis obliterans syndrome following lung transplantation

Bronchiolitis obliterans syndrome (BOS) is a common occurrence following lung transplantation and is one of the most important impediments to long-term graft viability. Cytolytic therapy has been used as treatment for BOS, but there is little data documenting efficacy. Furthermore, these agents have been associated with significant adverse effects. Charts of 15 patients who received an antilymphocyte preparation (ALP) for BOS were reviewed. Forced expiratory volume-1 second (FEV1) and stage of BOS were compared before and after treatment. Complications of ALP were recorded from the charts. Two of 15 patients had an improvement in FEV1, 5/15 exhibited no change, and 8/15 continued to decline. There was no pattern associating stage of BOS with likelihood of response to ALP. All patients received antimicrobial prophylaxis and did not experience infectious complications following administration of the ALP. ALP for the treatment of BOS results in an arrest or improvement of FEV1 in approximately 50% of patients. Infectious complications are uncommon when antimicrobial prophylaxis is administered.

Bronchodilator response at low lung volumes predicts bronchiolitis obliterans in lung transplant recipients

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is the major obstacle to long-term lung allograft viability. The diagnosis often occurs after significant organ dysfunction is present, and BOS is often unresponsive to standard immunosuppressive agents. We have observed bronchodilator responses (BRs) at low lung volumes in many of our patients who have developed BOS. We therefore assessed whether BR could predict the development of BOS.

METHODS

We conducted a retrospective review of the clinical and pulmonary function laboratory records of 146 patients who underwent transplantation between March 1983 and November 1993. BR was defined as 25% or more increase in forced expiratory flow at 50% of vital capacity or 30% or more increase in forced expiratory flow at 75% of vital capacity. BOS was defined according to recently published FEV1 criteria. Bronchiolitis obliterans was defined histologically according to criteria of the Lung Rejection Study Group.

RESULTS

Of the total population, 52 were excluded because of death or insufficient information. BRs of the small airways were seen in 31 patients (33%), 25 of whom developed BOS (83%). Approximately half of those with BR who developed BOS had evidence of acute rejection in the month prior to the onset of BR. Two thirds (four of six) of patients with BR not developing BOS had acute rejection in the previous month. The sensitivity of BR in predicting BOS was 51% with a specificity of 87%. The positive predictive value was 81%.

CONCLUSIONS

BR appears to be useful as an early marker of BOS. The development of BR in selected patients should lead to closer monitoring and possibly a trial of augmented immunosuppression to arrest the establishment of BOS.

Obliterative bronchiolitis after lung and heart-lung transplantation

Obliterative bronchiolitis (OB) has emerged as the main cause of morbidity and mortality in the long-term follow-up after lung and heart-lung transplantation. The pathogenesis of OB is multifactorial, with acute rejection and cytomegalovirus infection being the main risk factors for the development of OB. The final common pathway of all inciting events seems to be an alloimmune injury, with subsequent release of immunologic mediators and production of growth factors leading to luminal obliteration and fibrous scarring of the small airways. Analyzing the 14 years of experience in 163 patients at Stanford University, we found a current incidence of bronchiolitis obliterans syndrome or histologically proven OB within the first 3 years after lung and heart-lung transplantation of 36.3%, with an overall prevalence of 58.1% after heart-lung and 51.4% after lung transplantation. Both pulmonary function indices (forced expiratory flow between 25% and 75% of forced vital capacity and forced expiratory volume in 1 second) and transbronchial biopsies have proven helpful in diagnosing bronchiolitis obliterans syndrome or OB at an early stage. Early diagnosis of OB and improved management have achieved survival rates in patients with OB after 1, 3, 5, and 10 years of 83%, 66%, 46%, and 22%, compared with 86%, 83%, 67%, and 67% in patients without OB. Recently, different experimental models have been developed to investigate the cellular and molecular events leading to OB and to evaluate new treatment strategies for this complication, which currently limits the long-term success of heart-lung and lung transplantation.

Obliterative bronchiolitis after lung and heart-lung transplantation. An analysis of risk factors and management

With a prevalence of 34% (55/162 at-risk recipients) and a mortality of 25% (14/55 affected recipients), obliterative bronchiolitis is the most significant long-term complication after pulmonary transplantation. Because of its importance, we examined donor-recipient characteristics and antecedent clinical events to identify factors associated with development of obliterative bronchiolitis, which might be eliminated or modified to decrease its prevalence. We also compared treatment outcome between recipients whose diagnosis was made early by surveillance transbronchial lung biopsy before symptoms or decline in pulmonary function were present versus recipients whose diagnosis was made later when symptoms or declines in pulmonary function were present. Postoperative airway ischemia, an episode of moderate or severe acute rejection (grade III/IV), three or more episodes of histologic grade II (or greater) acute rejection, and cytomegalovirus disease were risk factors for development of obliterative bronchiolitis. Recipients with obliterative bronchiolitis detected in the preclinical stage were significantly more likely to be in remission than recipients who had clinical disease at the time of diagnosis: 81% (13/15) versus 33% (13/40); p < 0.05). These results indicate that acute rejection is the most significant risk factor for development of obliterative bronchiolitis and that obliterative bronchiolitis responds to treatment with augmented immunosuppression when it is detected early by surveillance transbronchial biopsy.

Particular phenotypic profile of blood lymphocytes during obliterative bronchiolitis syndrome following lung transplantation

Bronchiolitis obliterans syndrome (OBS) remains the major complication in long-term survivors with heart-lung transplants, occurring in up to 50% of patients who survived the first year postsurgery. Until now, a significant decrease in small airway flow parameters has represented the most sensitive index for the detection of early OBS. Using immunocytofluorometric analysis, in a prospective study we have analysed the phenotype of peripheral blood lymphocyte effector and regulatory subsets in seven patients with inactive well-established OBS as compared with lung transplant recipients without any complication. We found a particular phenotypic profile during well-established OBS characterized by: (1) the disappearance of the CD19+ B cell population despite normal or increased immunoglobulin blood levels; (2) a marked decrease in the CD4+/CD8+ ratio; (3) a dramatic increase in phenotypic cytotoxic effector T cells CD8+S6F1+high and CD3+CD4-CD8-; (4) a dramatic increase in the CD4+CD29+/CD4+CD45RA+ ratio associated with the loss of the phenotypic suppressor/inducer CD4+CD45RA+T cells. The results of this preliminary study suggest that, using this selected combination of lymphocyte membrane markers, sequential phenotyping could be useful in the noninvasive follow-up of lung transplant recipients. The predictive value of this phenotypic profile for the early diagnosis of OBS is under investigation.

Experimental large-animal model of obliterative bronchiolitis after lung transplantation

Obliterative bronchiolitis is a major cause of long-term morbidity after lung transplantation. It is characterized by small-airway inflammation and occlusion by fibrous tissue. The pathogenesis is uncertain. To study this disease, we developed a model of posttransplantation obliterative bronchiolitis using genetically defined miniature swine. Group 1 (n = 2) received a left lung autograft; group 2 (n = 7), a left lung allograft. Group 2 recipients were given cyclosporine, prednisone, and azathioprine for 3 months, then immunosuppression was tapered and discontinued over 1 month. The animals were observed for an additional 2 months, then sacrificed. Lung grafts in both groups were monitored with serial bronchoalveolar lavages and transbronchial biopsies for 6 months. After sacrifice, lung grafts underwent histopathologic and immunohistochemical examination. No allograft had histologic evidence of acute rejection or peribronchiolar infiltrate during the first 3 months of immunosuppression. During the tapering period, airway changes characterized by severe peribronchiolar lymphocytic infiltrates were seen. Bronchoalveolar lavages of allografts showed significantly increased lymphocyte counts with CD8+ cells predominating. After the discontinuation of immunosuppression, transbronchial biopsy and autopsy specimens showed progressive fibrous inflammatory occlusion of bronchioles. Immunohistochemical staining demonstrated increased expression of MCH class II antigen on the bronchiolar epithelium and increased dendritic cells and CD4+ lymphocytes. None of these changes were seen in group 1. Our findings suggest obliterative bronchiolitis is an immunologically mediated phenomenon related to chronic graft rejection after lung transplantation. This model will allow systematic study of the pathogenesis of obliterative bronchiolitis and possible therapeutic intervention.

Can immunohistological analysis of transbronchial biopsy specimens predict responder status in early acute rejection of lung allografts?

Acute cellular rejection (ACR) in the early posttransplant period is recognized as one predictor of the development of bronchiolitis obliterans in lung transplant recipients. Using an immunohistochemical panel of antibodies to CD3, L26, HLA-DR, collagenase IV, proliferating cell nuclear antigen (PCNA), KPI, and S100 antigens we analyzed cases of moderate ACR that did respond (n = 11) and that did not respond (n = 10) to bolus solumedrol therapy early in the postoperative period (< 100 days) to determine if we could identify predictors of histological response. Responders who had follow-up negative biopsies after therapy had biopsy specimens containing an average of 41.1% T cells (range, 15.1 to 69.8), 8.8% B cells (range, 0.6 to 20), 18.1% HLA-DR-positive cells (range, 3 to 29.6), 12.2% PCNA-positive cells (range, 2.7 to 22.6), 8.9% collagenase IV-positive cells (range, 0.7 to 20.9), and rare dendritic cells. Nonresponders who had follow-up biopsies that failed to show a significant change in rejection grade had biopsy specimens with the following average cell profiles: 35.8% T cells (range, 7 to 70.7), 21.6% B cells (range, 3.7 to 39.5), 14.2% HLA-DR-positive cells (range, 1.8 to 24.7), 11.4% PCNA-positive cells (range, 0.8 to 22), 12.6% collagenase IV-positive cells (range, 0.6 to 34.1), and occasional dendritic cells. Statistical analysis suggested that large numbers of B lymphocytes in early acute rejection predicts non-responsiveness to interventional immunosuppressive therapy and may indicate a significant role of humoral rejection in the behavior of early allograft rejection.

Lung transplantation

Solid-organ transplantation has flourished during the last decade, with transplantation of heart and lungs becoming available to patients with end-stage cardiac or pulmonary diseases. The first lung transplant was performed in 1963 on a 58-year-old man with bronchogenic carcinoma. He survived for 18 days. During the next two decades, approximately 40 lung transplant procedures were attempted without success. These early attempts at lung transplantation were unsuccessful because of the development of lung rejection, anastomotic complications, or infection in the transplant recipients. In the early 1980s, human heart-lung transplantation was successfully performed for the treatment of pulmonary vascular disease. After this procedure, single-lung transplantation for the treatment of end-stage interstitial lung disease and obstructive lung disease was developed. More recently, the technique of double-lung transplantation has come into existence. This article reviews various aspects of lung transplantation, including immunosuppression, lung graft preservation, the various surgical techniques and types of lung transplant procedures available, recipient and donor selection criteria, and postoperative care of the transplant recipient. In addition, infectious and noninfectious complications seen in this particular patient population, including acute and chronic rejection, will be discussed.

Management of lung transplant rejection

Using current immunosuppressive protocols, rejection is common after lung transplantation. Most recipients have at least one episode of acute rejection, and approximately 25 percent of recent long-term survivors have developed chronic rejection. Acute rejection has usually been reversible with treatment, but chronic rejection has responded poorly, relapsed frequently, and been one of the leading causes of late morbidity and mortality. Appropriate management of rejection is predicated on timely, accurate diagnosis. Clinical criteria for the diagnosis of acute rejection are useful but nonspecific, and TBB has emerged as the procedure of choice for diagnosing acute rejection and infection. Chronic rejection is manifested by OB and is characterized physiologically by the development of airflow obstruction. Although histologic confirmation is preferable, the sensitivity of TBB for the detection of OB has been inconsistent, and the specificity has been low. Lung transplantation has indeed come of age, but understanding the immunopathogenesis and improving the clinical management of rejection remain major challenges for the next decade.