Role of defensins in the pathogenesis of chronic lung allograft rejection.

Chronic rejection predominantly manifested as bronchiolitis obliterans syndrome (BOS), still remains a major problem affecting long-term outcomes in human lung transplantation (LTx). Donor specific antibodies (DSA) and infiltration of neutrophils in the graft have been associated with the development of BOS. This study determines the role of defensins, produced by neutrophils, and its interaction with α-1-antitrypsin (AAT) towards induction of airway inflammation and fibrosis which are characteristic hallmarks of BOS. Bronchoalveolar lavage (BAL) and serum from LTx recipients, BOS+ (n=28), BOS- (n=26) and normal healthy controls (n=24) were analyzed. Our results show that BOS+ LTx recipients had higher α-defensins (HNP1-3) and ß-defensin2 HBD2 concentration in BAL and serum compared to BOS-DSA-recipients and normal controls (p=0.03). BOS+ patients had significantly lower serum AAT along with higher circulating concentration of HNP-AAT complexes in BAL (p=0.05). Stimulation of primary small airway epithelial cells (SAECs) with HNPs induced expression of HBD2, adhesion molecules (ICAM and VCAM), cytokines (IL-6, IL-1ß, IL-13, IL-8 and MCP-1) and growth-factor (VEGF and EGF). In contrast, anti-inflammatory cytokine, IL-10 expression decreased 2-fold (p=0.002). HNPs mediated SAEC activation was completely abrogated by AAT. In conclusion, our results demonstrates that neutrophil secretory product, α-defensins, stimulate ß-defensin production by SAECs causing upregulation of pro-inflammatory and pro-fibrotic signaling molecules. Hence, chronic stimulation of airway epithelial cells by defensins can lead to inflammation and fibrosis the central events in the development of BOS following LTx.

Acute antibody-mediated rejection after lung transplantation.

BACKGROUND: Antibody-mediated rejection (AMR) after lung transplantation remains enigmatic, and there is no consensus on the characteristic clinical, immunologic and histologic features. METHODS: We performed a retrospective, single-center cohort study and identified cases of acute AMR based on the presence of circulating donor-specific human leukocyte antigen (HLA) antibodies (DSA), histologic evidence of acute lung injury, C4d deposition and clinical allograft dysfunction. RESULTS: We identified 21 recipients with acute AMR based on the aforementioned criteria. AMR occurred a median 258 days after transplantation; 7 recipients developed AMR within 45 days of transplantation. All patients had clinical allograft dysfunction, DSA, histology of acute lung injury and capillary endothelial C4d deposition. Fifteen recipients improved clinically and survived to hospital discharge, but 6 died of refractory AMR. One survivor had bronchiolitis obliterans syndrome at the time of AMR diagnosis; 13 of the 14 remaining survivors developed chronic lung allograft dysfunction (CLAD) during follow-up. Overall, 15 recipients died during the study period, and the median survival after the diagnosis of AMR was 593 days. CONCLUSIONS: Acute AMR can be a fulminant form of lung rejection, and survivors are at increased risk of developing CLAD. The constellation of acute lung injury, DSA and capillary endothelial C4d deposition is compelling for acute AMR in recipients with allograft dysfunction. This clinicopathologic definition requires validation in a multicenter cohort, but may serve as a foundation for future studies to further characterize AMR.

The impact of induction on survival after lung transplantation: an analysis of the International Society for Heart and Lung Transplantation Registry.

BACKGROUND: The use of induction immunosuppression after lung transplantation remains controversial. In this study, we examined the impact of induction on survival after lung transplantation. METHODS: We performed a retrospective cohort study of 3970 adult lung transplant recipients reported to the ISHLT Registry. We divided the cohort into three groups based on the use of induction: none, interleukin-2 receptor antagonists (IL-2 RA), and polyclonal antithymocyte globulins (ATG). We estimated graft survival using the Kaplan-Meier method and constructed a multivariable Cox proportional hazards model to examine the impact of induction on graft survival in the context of other variables. RESULTS: During the study period, 2249 patients received no induction, 1124 received IL-2 RA, and 597 received ATG. Four years after transplantation, recipients treated with IL-2 RA had better graft survival (64%) than those treated with ATG (60%) and those who did not receive induction (57%; log rank p = 0.0067). This survival advantage persisted in the multivariable model for single and bilateral recipients treated with IL-2 RA compared to those who did not receive induction (RR = 0.82, p = 0.007). Similarly, bilateral recipients treated with ATG had a survival advantage over bilateral recipients who did not receive induction (RR = 0.78, p = 0.043), but single lung recipients treated with ATG did not have a survival advantage over single lung recipients who did not receive induction (RR = 1.06, p = 0.58). CONCLUSIONS: Induction with lL-2 RA for single and bilateral lung recipients and induction with ATG for bilateral recipients are associated with a survival benefit, independent of other variables that might impact survival.

Correlation between interleukin-15 and granzyme B expression and acute lung allograft rejection.

The levels of interleukin (IL)-15 and granzyme B mRNA expression have been correlated with acute rejection episodes of kidney and heart allografts. Thus, the purpose of this study was to determine whether a correlation exists between the expression of IL-15 and granzyme B and acute lung allograft rejection. Toward this, the levels of IL-15 and granzyme B mRNA expression were determined in bronchoalveolar lavage-derived alveolar macrophages and total cells, respectively, from lung transplant patients with stable lung allograft function and patients undergoing acute rejection episodes. The expression levels of IL-15 mRNA was significantly higher in the patients undergoing acute rejection as compared to patients with stable lung function (P=0.02). The expression levels of granzyme B mRNA was also significantly higher in the patients undergoing acute rejection as compared to patients with stable lung function (P=0.005). The Receiver-Operating-Characteristic curve demonstrated that acute rejection can be predicted with a sensitivity of 94% and specificity of 67% with the use of a cutoff value of 3.1 fg of granzyme B mRNA per microgram of total RNA (or 71% sensitivity and 75% specificity of a cutoff value of 9.1 fg/microg). These data indicate that IL-15 secreted by activated alveolar macrophages and granzyme B secreted by activated CD8+ cytotoxic T lymphocytes play important roles in the process of acute lung allograft rejection.

Interleukin-6 and interferon-gamma gene polymorphisms in the development of bronchiolitis obliterans syndrome after lung transplantation.

BACKGROUND: A number of genetic polymorphisms have been shown to regulate the production and secretion of tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, interferon (IFN)-gamma, interleukin (IL)-6, and IL-10. Several of these genetic polymorphisms have been shown to be associated with either acute or chronic rejection of kidney, liver, and heart allografts and with development of allograft fibrosis after lung transplantation. The aim of this study was to assess the effect of these genetic polymorphisms on the development of bronchiolitis obliterans syndrome (BOS) after lung transplantation. METHODS: Genetic polymorphisms were detected by means of polymerase chain reaction in 93 lung allograft recipients for functional polymorphisms in the TNF-alpha (-308), TGF-beta1 (+869 and +915), IL-6 (-174), IFN-gamma (+874), and IL-10 (-1082, -819, and -592) genes. Then, a correlation between BOS development and the presence of these cytokine genotypes was determined using Kaplan-Meier actuarial analysis. RESULTS: A significant correlation was detected between the presence of high-expression polymorphisms of the IL-6 and IFN-gamma genes and BOS development after lung transplantation (P =0.045 and 0.039, respectively). Also, patients with high-expression polymorphisms in both genes developed BOS significantly earlier than patients with low-expression polymorphisms in one or both genes, suggesting a synergistic effect of the alleles during BOS pathogenesis (P =0.016). No correlation was detected between polymorphisms of the TNF-alpha, TGF-beta1, and IL-10 genes and development of BOS after lung transplantation. CONCLUSIONS: The presence of high-expression polymorphisms at position -174 of the IL-6 gene and position +874 of the IFN-gamma gene significantly increases the risk for BOS development after lung transplantation.

Outcome of patients with cystic fibrosis awaiting lung transplantation.

Cystic fibrosis is a common indication for lung transplantation. Under the current organ allocation system, donor lungs are distributed to patients based solely on their accrued waiting time, and the death rate on the waiting list has been high. Physiologic parameters have been used to guide the referral, but risk factors for death while awaiting transplantation have not been well defined. This study aimed to identify factors at the time of evaluation that were associated with death on the waiting list. A consecutive cohort of 146 patients with cystic fibrosis who were listed for lung transplantation was retrospectively reviewed. Characteristics of patients who died awaiting transplantation were compared with those of patients who survived until transplantation or the end of the study. Thirty-seven patients died while waiting, 76 underwent transplantation, and 33 were alive and still waiting. Actuarial survival rates for the entire cohort were 81% at 1 yr, 67% at 2 yr, and 59% at 3 yr. Although a multivariate Cox proportional hazards model (chi(2) = 29.6; p < 0.001) identified shorter six-minute walk distance (50 m increments; RR, 0.69; 95% CI, 0.57 to 0.84), higher systolic pulmonary artery pressure (5 mm Hg increments; RR, 1.41; 95% CI, 1.11 to 1.80), and diabetes mellitus (RR, 1.57; 95% CI, 1.06 to 2.32) as significant risk factors for death on the waiting list, these factors and other features overlapped considerably between the group of patients who died waiting and the group who lived until transplantation or the end of the study. The transplant evaluation selects a rather homogeneous cohort of patients for the waiting list. Unless outcome on the waiting list can be reliably predicted, establishing criteria to allocate donor lungs according to medical urgency may not be feasible.