HLA-specific antibodies are risk factors for lymphocytic bronchiolitis and chronic lung allograft dysfunction

Acute antibody-mediated rejection after lung transplantation

The role of humoral immunity after lung transplantation remains unclear. In this report, we describe the pathologic findings and clinical course of a case of acute antibody-mediated rejection (AMR) after lung transplantation. After an uncomplicated early course, a 31-year-old man with cystic fibrosis developed acute graft dysfunction 1 month after bilateral lung transplantation. Lung biopsies showed acute pneumonitis with capillary injury, neutrophilic infiltration and nuclear dust. Immunostaining for C4d demonstrated endothelial cell deposition, and circulating donor-specific human leukocyte antigen (HLA) antibodies were identified. Despite severe hypoxemic respiratory failure, he responded well to a regimen consisting of methylprednisolone, plasma exchange, intravenous immunoglobulin and rituximab therapy. He completely recovered clinically although donor-specific HLA antibodies have remained detectable. The incidence of acute AMR after lung transplantation is unknown, but this case fulfills all of the consensus diagnostic criteria, and we suggest that AMR could be an under-recognized cause of acute graft dysfunction.

Bronchiolitis obliterans syndrome: alloimmune-dependent and -independent injury with aberrant tissue remodeling

Long-term success in lung transplantation continues to be challenged by chronic graft dysfunction, which is manifest as bronchiolitis obliterans syndrome (BOS). The mechanisms of BOS involve both immune-mediated pathways (rejection, autoimmune-like mechanisms), and alloimmune-independent pathways (infection, aspiration, ischemia, primary graft failure), which lead to a fibroproliferative responses. BOS correlates histologically with obliterative bronchiolitis in terminal bronchioles and evidence of aberrant remodeling in the airway epithelium, vasculature, stroma, and lymphoid system. A potentially important mechanism that supports the progressive and therapy-resistant nature of BOS is a continuous cycle of ongoing injury and aberrant remodeling. Namely, anatomical and functional abnormalities induce and exacerbate immune-mediated and alloimmune-independent pathways through various mechanisms (e.g., epithelial remodeling decreases mucociliary clearance that exacerbates aspiration-related injury). From this viewpoint, we review current therapeutic strategies and revisit the role of transplant surgeons in attenuating the initial transplant-related injuries to prevent the lung grafts from entering the remodeling-injury cycle.

Late primary graft dysfunction after lung transplantation and bronchiolitis obliterans syndrome

Primary graft dysfunction (PGD) is a common early complication after lung transplantation. We conducted a retrospective cohort study of 334 recipients to evaluate the impact of PGD graded at 24, 48 and 72 h on the risk of bronchiolitis obliterans syndrome (BOS) development (stage 1) and progression (stages 2 and 3). We constructed multivariable Cox proportional hazards models to determine the risk of BOS attributable to PGD in the context of other potential risk factors including acute rejection, lymphocytic bronchitis and respiratory viral infections. All grades of PGD at all time points were significant risk factors for BOS development and progression independent of acute rejection, lymphocytic bronchitis and respiratory viral infections. Specifically, PGD grade 1 at T24 was associated with a relative risk of BOS stage 1 of 1.93, grade 2 with a relative risk of 2.29 and grade 3 with a relative risk of 3.31. Furthermore, this direct relationship between the severity of PGD and the risk of BOS persisted at all time points. We conclude that all grades of PGD at all time points are independent risk factors for BOS development and progression. Future strategies that might attenuate the severity of PGD may mitigate the risk of BOS.

Human leukocyte antigen antibodies and chronic rejection: from association to causation

Considerable research has established an association between human leukocyte antigen antibodies and chronic rejection. Two new major developments now provide evidence that this relationship is in fact causative. First, recent studies of serial serum samples of 346 kidney transplant patients from four transplant centers show that de novo antibodies, can be detected before rejection. Moreover, serial testing revealed that when antibodies were not present, 528 patient years of good function was demonstrable in 149 patients. Second, among 90 patients whose grafts chronically failed, 86% developed antibodies before failure. To assess the likelihood of a causal link, we applied the nine widely accepted Bradford Hill criteria and conclude that the evidence supports a causal connection between human leukocyte antigen antibodies and chronic rejection. The clinical implication is significant because we hope this review will stimulate centers to begin the one remaining task of showing that antibody removal will indeed prevent chronic failure.

Critical role of effector macrophages in mediating CD4-dependent alloimmune injury of transplanted liver parenchymal cells

Despite the recognition that humoral rejection is an important cause of allograft injury, the mechanism of Ab-mediated injury to allograft parenchyma is not well understood. We used a well-characterized murine hepatocellular allograft model to determine the mechanism of Ab-mediated destruction of transplanted liver parenchymal cells. In this model, allogeneic hepatocytes are transplanted into CD8-deficient hosts to focus on CD4-dependent, alloantibody-mediated rejection. Host serum alloantibody levels correlated with in vivo allospecific cytotoxic activity in CD8 knockout hepatocyte rejector mice. Host macrophage depletion, but not CD4(+) T cell, NK cell, neutrophil, or complement depletion, inhibited in vivo allocytotoxicity. Recipient macrophage deficiency delayed CD4-dependent hepatocyte rejection and inhibited in vivo allocytotoxicity without influencing alloantibody production. Furthermore, hepatocyte coincubation with alloantibody and macrophages resulted in Ab-dependent hepatocellular cytotoxicity in vitro. These studies are consistent with a paradigm of acute humoral rejection in which CD4(+) T cell-dependent alloantibody production results in the targeting of transplanted allogeneic parenchymal cells for macrophage-mediated cytotoxic immune damage. Consequently, strategies to eliminate recipient macrophages during CD4-dependent rejection pathway may prolong allograft survival.

Immunological link between primary graft dysfunction and chronic lung allograft rejection

BACKGROUND

Primary graft dysfunction (PGD) in the immediate post-lung transplant period strongly increases the risk of chronic rejection (broncholitis obliterans syndrome). Here, we hypothesized that PGD-induced inflammation augments alloimmunity, thereby predisposing to broncholitis obliterans syndrome.

METHODS

Primary graft dysfunction and broncholitis obliterans syndrome were diagnosed according to the established International Society for Heart and Lung Transplantation criteria. Anti-human leukocyte antigen (HLA) alloantibodies were analyzed using Flow-PRA. Donor HLA class II-specific T cells were analyzed using interferon (IFN)-gamma ELISPOT. Serum levels of 25 cytokines and chemokines were measured using LUMINEX.

RESULTS

Of the 127 subjects, 29 (22.8%) had no PGD (grade 0), 42 (33.2%) had PGD-1, 36 (28.3%) had PGD-2, and 20 (15.7%) had PGD-3. Patients with PGD grades 1 to 3 (PGD(1-3)) had elevated proinflammatory mediators MCP-1, IP-10, interleukin (IL)-1 beta, IL-2, IFN-gamma, and IL-12 in the sera during the early posttransplant period compared with patients with PGD grade 0 (PGD(0)). On serial analysis, PGD(1-3) patients revealed increased development of de novo anti-HLA-II (5 years: 52.2% versus PGD(0) 13.5%, p = 0.008). However, no difference was found in anti-HLA-I alloantibody development (PGD(1-3) patients 48% versus PGD(0) 39.6%, p = 0.6). Furthermore, PGD(1-3) patients had increased frequency of donor HLA class II-specific CD4(+) T cells [(91.4 +/- 19.37) x 10(-6) versus (23.6 +/- 15.93) x 10(-6), p = 0.003].

CONCLUSIONS

Primary graft dysfunction induces proinflammatory cytokines that can upregulate donor HLA-II antigens on the allograft. Increased donor HLA-II expression along with PGD-induced allograft inflammation promotes the development of donor specific alloimmunity. This provides an important mechanistic link between early posttransplant lung allograft injury and reported association with broncholitis obliterans syndrome.

De novo production of K-alpha1 tubulin-specific antibodies: role in chronic lung allograft rejection

Lung transplantation is the treatment option for a variety of end-stage pulmonary diseases. Posttransplant development of Abs against donor HLA and non-HLA Ags have been associated with acute and chronic rejection of transplanted organs. Development of bronchiolitis obliterans syndrome (BOS) following lung transplantation has been correlated with de novo production of anti-donor-HLA Abs. However, only a portion of the patients with BOS demonstrate detectable anti-donor-HLA Abs. Airway epithelium is considered as a major target for lung allograft rejection. In this study we demonstrate that many BOS(+) patients (12 of 36) develop Abs reactive to epithelial cell Ag that are distinct from HLA. Furthermore, de novo production of antiepithelial cell Ab precedes clinical onset of BOS. N-terminal sequencing and blastx analysis as well as blocking with K-alpha1 tubulin-specific Ab identified the epithelial Ag as K-alpha1 tubulin. Binding of the de novo-produced anti-K-alpha1 tubulin Abs to the airway epithelial cells resulted in the increased expression of transcription factors (TCF5 and c-Myc), leading to increased expression of fibrogenic growth factors, activation of cell cycle signaling, and fibroproliferation, the central events in immunopathogenesis of BOS following human lung transplantation.

IL-17-dependent cellular immunity to collagen type V predisposes to obliterative bronchiolitis in human lung transplants

Bronchiolitis obliterans syndrome (BOS), a process of fibro-obliterative occlusion of the small airways in the transplanted lung, is the most common cause of lung transplant failure. We tested the role of cell-mediated immunity to collagen type V [col(V)] in this process. PBMC responses to col(II) and col(V) were monitored prospectively over a 7-year period. PBMCs from lung transplant recipients, but not from healthy controls or col(IV)-reactive Goodpasture's syndrome patients after renal transplant, were frequently col(V) reactive. Col(V)-specific responses were dependent on both CD4+ T cells and monocytes and required both IL-17 and the monokines TNF-alpha and IL-1beta. Strong col(V)-specific responses were associated with substantially increased incidence and severity of BOS. Incidences of acute rejection, HLA-DR mismatched transplants, and induction of HLA-specific antibodies in the transplant recipient were not as strongly associated with a risk of BOS. These data suggest that while alloimmunity initiates lung transplant rejection, de novo autoimmunity mediated by col(V)-specific Th17 cells and monocyte/macrophage accessory cells ultimately causes progressive airway obliteration.

A single human leukocyte antigen-antibody test after heart or lung transplantation is predictive of survival

A single posttransplant test for human leukocyte antigen (HLA) antibodies in heart and lung graft patients was examined for its predictive value for graft survival as part of the 13th and 14th international histocompatibility workshops. We included patients with HLA antibodies who were tested 6 or more months after transplantation. They were followed for 3 to 5 years. Kaplan-Meier survival curves were used to analyze the data. Of the 235 heart transplant patients, 24.7% had HLA antibodies, whereas 13.3% of the 150 lung transplant recipients, tested positive for HLA antibodies. Heart transplant patients with antibodies had a 5-year survival of 42% vs. 58% for those without antibodies (P=0.0065). For lung transplant patients, the 5-year graft survival was 27% for those with antibodies vs. 56% for those without (P<0.0001). These results indicate that for heart and lung transplant patients, a single test after transplantation of HLA antibodies is predictive of graft survival.

Pediatric lung transplantation: perspectives for the pathologist

Lung transplantation offers life-saving and life-extending treatment for children and adolescents with congenital and acquired forms of pulmonary and pulmonary vascular disease, for whom medical therapy is ineffective or insufficient for sustained response. This review summarizes the pathology related to lung transplantation for the practicing pediatric pathologist and also highlights aspects of lung transplantation unique to the pediatric population. Clinical issues related to availability of organs, candidate eligibility, surgical technique, and postoperative monitoring are discussed. Pathologic evaluation of routine surveillance transbronchial biopsies requires attention to acute cellular rejection, opportunistic infection, and other forms of acute and resolving lung injury. These findings are correlated in some cases with endobronchial biopsies and bronchoalveolar lavage as adjunctive tools in surveillance. Open or thoracoscopic biopsies also have diagnostic utility in cases with acute or chronic graft deterioration of uncertain etiology. Future challenges in pediatric lung transplantation are similar to those in the adult population, with continued efforts focused on prolonging graft survival, prevention of bronchiolitis obliterans syndrome due to chronic cellular rejection, and evaluation of humoral rejection.

Severity of lymphocytic bronchiolitis predicts long-term outcome after lung transplantation

RATIONALE

Severe and recurrent acute vascular rejection of the pulmonary allograft is an accepted major risk factor for obliterative bronchiolitis.

OBJECTIVES

We assessed the role of lymphocytic bronchiolitis as a risk factor for bronchiolitis obliterans syndrome (BOS) and death after lung transplantation.

METHODS

Retrospective analysis of 341 90-day survivors of lung transplant performed in 1995-2005 who underwent 1,770 transbronchial lung biopsy procedures.

MEASUREMENTS AND MAIN RESULTS

Transbronchial biopsies showed grade B0 (normal) (n = 501), B1 (minimal) (n = 762), B2 (mild) (n = 176), B3 (moderate) (n = 70), B4 (severe) (n = 4) lymphocytic bronchiolitis, and Bx (no bronchiolar tissue) (n = 75). A total of 182 transbronchial biopsies were ungraded (8 inadequate, 142 cytomegalovirus, 32 other diagnoses). Lung transplant recipients were grouped by highest B grade before diagnosis of BOS: B0 (n = 12), B1 (n = 166), B2 (n = 89), and B3-B4 (n = 51). Twenty-three were unclassifiable. Cumulative incidence of BOS and death were dependent on highest B grade (Kaplan-Meier, P < 0.001, log-rank). Multivariable Cox proportional hazards analysis showed significant risks for BOS were highest B grade (relative risk [RR], 1.62; 95% confidence interval [CI], 1.31-2.00) (P < 0.001), longer ischemic time (RR, 1.00; CI, 1.00-1.00) (P < 0.05), and recent year of transplant (RR, 0.93; CI, 0.87-1.00) (P < 0.05), whereas risks for death were BOS as a time-dependent covariable (RR, 19.10; CI, 11.07-32.96) (P < 0.001) and highest B grade (RR, 1.36; CI, 1.07-1.72) (P < 0.05). Acute vascular rejection was not a significant risk factor in either model.

CONCLUSIONS

Severity of lymphocytic bronchiolitis is associated with increased risk of BOS and death after lung transplantation independent of acute vascular rejection.

Posttransplant monitoring of pediatric lung transplant recipients

PURPOSE OF REVIEW

This article reviews current trends in pediatric lung posttransplant management, reveals pitfalls that exist, and introduces additional parameters that may have an impact on long-term survival.

RECENT FINDINGS

A number of parameters are monitored after transplantation to prevent or identify early complications related to lung transplantation in hope of reducing morbidity and mortality. These include routine laboratory studies, imaging, and monitoring of drug levels and lung function. Drug monitoring allows individualization of a patient's immunosuppressive therapy; however, drug levels alone may not reflect the patient's immune status. ImmuKnow is a general immune-monitoring assay that may help guide therapy. Two major complications are rejection and infection, and bronchoscopy is used to differentiate these two entities. Silent rejection may occur and increase the chance of developing bronchiolitis obliterans; therefore, many centers perform surveillance bronchoscopies. Recently, de-novo anti-histocompatibility locus antigen antibodies and gastroesophageal reflux have been associated with poor outcomes, and many centers are monitoring these entities as part of care following lung transplant.

SUMMARY

There has been little improvement in long-term outcomes of lung transplantation. Current monitoring methods are utilized to maintain or improve outcomes and recently additional monitoring parameters have been identified which hopefully will improve long-term outcomes.

Role of Flow Cytometry to Define Unacceptable HLA Antigens in Lung Transplant Recipients with HLA-Specific Antibodies

BACKGROUND

Antidonor HLA-specific antibodies have been associated with hyperacute rejection and primary graft failure in lung transplant recipients. Thus, transplant candidates with HLA-specific antibodies generally undergo prospective crossmatching to exclude donors with unacceptable HLA antigens. However, the need to perform a prospective crossmatch limits the donor pool and is associated with increased waiting list times and mortality. A virtual crossmatch strategy using flow cytometry, which enables precise determination of HLA-specific antibody specificity, was compared to prospective crossmatching in sensitized lung transplant candidates.

METHODS

In all, 341 lung transplant recipients were analyzed retrospectively (April 1992 to July 2003). Sixteen patients with HLA-specific antibodies underwent transplantation based on flow cytometric determination of antibody specificity and 10 underwent prospective crossmatching.

RESULTS

Freedom from bronchiolitis obliterans syndrome (BOS) at three years was similar in those undergoing a virtual crossmatch, those undergoing prospective crossmatching, and those without HLA-specific antibodies (80.4% +/- 13.4, 85.7% +/- 13.2, and 73.8% +/- 2.8, respectively, P = 0.88). Three-year survival was also comparable (87.5% +/- 8.3, 70.0% +/- 14.5, and 78.5% +/- 2.4, respectively, P = 0.31). Elimination of prospective crossmatching for sensitized patients was associated with a significant decrease in time on the waiting list (P < 0.01) and in waiting list mortality (P < 0.05). All 16 patients undergoing a virtual crossmatch had negative retrospective crossmatches.

CONCLUSIONS

By carefully determining the specificity of HLA-specific antibodies, flow cytometry methodologies enable the prediction of negative crossmatch results with up to 100% accuracy, enabling the determination of appropriateness of donors. Using this virtual crossmatch strategy, crossmatching can be safely omitted prior to lung transplantation, thereby decreasing waiting list time and mortality rates for candidates with HLA-specific antibodies.

Anti-HLA alloantibodies in pediatric solid organ transplantation

An increasing number of studies demonstrate the clinical impact of preformed and de novo anti-human leucocyte antigen alloantibody (HLA-Ab) in solid organ transplantation (Tx). The screening of HLA-Ab in candidates and transplant recipients has evolved over time, with continuous improvement in the sensitivity and specificity of assays for HLA-Ab detection. Furthermore, histologic markers of complement activation pathways are currently implemented in the diagnosis of antibody-mediated rejection (AMR). Therapeutic strategies, including depletion of HLA-Ab and B cells, have allowed Tx across antibody barriers, or have rescued patients with AMR. The purpose of the present review is to summarize the state-of-the-art of HLA-Ab detection, clinical significance and therapeutic strategies in pediatric solid organ Tx.

Allograft Rejection After Lung Transplantation

Lung transplantation has become an accepted therapy for selected patients with advanced lung disease. One of the main limitations to successful lung transplantation is rejection of the transplanted organ. This article discusses the clinical presentation, treatment, and prevention of hyperacute, acute, and chronic rejection in the lung transplant recipient.

Humoral theory of transplantation: further evidence

In the two and a half years following our initial paper on the humoral theory of transplantation, many publications have emerged in support of the hypothesis, with no studies in opposition. It is accepted that the role of antibodies is incontrovertible in hyperacute rejection, although what fraction of acute rejection is humoral remains to be determined. A recent large-scale prospective trial showing that transplant patients with antibodies have twice the failure rate as those without antibodies suggests that chronic rejection is also caused by antibodies. Together with serum creatinine, HLA antibodies are, therefore, the best predictor of graft function in kidney patients.

C4d deposition in lung allografts is associated with circulating anti-HLA alloantibody

The complement activation demonstrated by vascular C4d deposition is used to diagnose antibody-mediated rejection (AMR) in renal allografts, but remains controversial in lung transplantation (LTX).

METHODS

C4d deposition was assessed by immunohistochemistry in 192 lung transplant biopsies from 32 patients. ELISA analysis was performed on 415 serum samples in those 32 temporally and rejection-grade matched LTX patients; 16 patients developed HLA-Ab, while the other 16 patients remained negative. The specificity of C4d staining was further compared in 18 additional LTX patients without HLA-Ab or acute cellular rejection (ACR), but in the presence of CMV-pneumonitis or reperfusion injury.

RESULTS

Specific subendothelial C4d deposition was seen in 5 of 16 (31%) patients with HLA-Ab and was absent in 16 patients without HLA-Ab (p<0.05). All patients with specific C4d deposition exhibited donor-specific HLA-Ab. There were 13 patients with bronchiolitis obliterans syndrome in the group of 16 HLA-Ab positive patients, versus 2/16 in ELISA-negative patients (p<0.005). One of 7 patients with CMV pneumonitis and 2 of 11 patients with reperfusion injury also showed C4d positivity (not statistically significant).

CONCLUSIONS

In this study, specific subendothelial C4d deposition was a marker for the involvement of HLA-Ab in lung allograft rejection. The patchy nature, low sensitivity, and specificity of C4d staining might limit clinical use in protocol biopsies. However, in patients with decreasing pulmonary function, refractory ACR and/or HLA-Ab, specific C4d deposition may serve as a marker of coexistent AMR.

Phenotype of airway epithelial cells suggests epithelial to mesenchymal cell transition in clinically stable lung transplant recipients

BACKGROUND

Obliterative bronchiolitis in chronic rejection of lung allografts is characterised by airway epithelial damage and fibrosis. The process whereby normal epithelium is lost and replaced by fibroblastic scar tissue is poorly understood, but recent findings suggest that epithelial cells can become fibroblasts through epithelial-mesenchymal transition (EMT). It is hypothesised that EMT occurs in lung allografts and plays a potential role in airway remodelling.

METHODS

Sixteen stable lung transplant recipients underwent bronchoscopy with bronchoalveolar lavage (BAL), endobronchial biopsies, and bronchial brushings. Biopsy sections were stained for the fibroblast marker S100A4. Brushings were cultured on collagen, stained with anti-S100A4, and examined for further EMT markers including matrix metalloproteinase (MMP) zymographic activity and epithelial invasion through collagen coated filters.

RESULTS

A median 15% (0-48%) of the biopsy epithelium stained for S100A4 in stable lung transplant recipients and MMP-7 co-localisation was observed. In non-stimulated epithelial cultures from lung allografts, S100A4 staining was identified with MMP-2 and MMP-9 production and zymographic activity. MMP total protein and activity was increased following stimulation with transforming growth factor (TGF)-beta1. Non-stimulated transplant epithelial cells were invasive and penetration of collagen coated filters increased following TGF-beta1 stimulation.

CONCLUSIONS

This study provides evidence of EMT markers in lung allografts of patients without loss of lung function. The EMT process may represent a final common pathway following injury in more common diseases characterised by airway remodelling.

Bronchiolitis Obliterans Syndrome

Post-transplantation bronchiolitis obliterans syndrome (BOS) is a clinicopathological syndrome characterised histologically by obliterative bronchiolitis (OB) and physiologically by airflow limitation. It affects long-term survival with no consistently effective treatment strategy.An updated review of risk factors for OB/BOS, and approaches to prevention and treatment was performed through a systematic review of relevant studies between January 1990 and February 2005. The initial search identified 853 publications, with 56 articles reviewed after exclusions. Early acute rejection is the most significant risk factor, with late rejection (> or =3 months) also significant. Lymphocytic bronchitis/bronchiolitis is relevant, with later onset associated with greater risk. Viral infections are identified as significant risk factors. Human leukocyte antigen matching and OB/BOS development is a weaker association, but is stronger with acute rejection. Recipient and donor characteristics have a minor role. There is limited evidence that altering immunosuppression is effective in reducing the rate of decline in lung function. BOS reflects an allo-immunological injury, possibly triggered by cytomegalovirus and respiratory viral infections, or noninfectious injury. Immunological susceptibility may be reflected by more frequent acute rejection episodes. Preventative and therapeutic modifications in immunosuppression remain important. Identifying markers of immunological susceptibility and, hence, risk stratification requires further research.