Impact of HLA Compatibility on Lung Transplant Survival and Evidence for an HLA Restriction Phenomenon: A Collaborative Transplant Study Report

Description and first insights on a large genomic biobank of lung transplantation

The main limitation to long-term lung transplant (LT) survival is chronic lung allograft dysfunction (CLAD), which leads to irreversible lung damage and significant mortality. Individual factors can impact CLAD, but no large genetic investigation has been conducted to date. We established the multicentric Genetic COhort in Lung Transplantation (GenCOLT) biobank from a rich and homogeneous sub-part of COLT cohort. GenCOLT collected DNA, high-quality GWAS (genome-wide association study) genotyping and robust HLA data for donors and recipients to supplement COLT clinical data. GenCOLT closely mirrors the global COLT cohort without significant variations in variables like demographics, initial disease and survival rates (P > 0.05). The GenCOLT donors were 45 years-old on average, 44% women, and primarily died of stroke (54%). The recipients were 48 years-old at transplantation on average, 45% women, and the main underlying disease was chronic obstructive pulmonary disease (45%). The mean follow-up time was 67 months and survival at 5 years was 57.3% for the CLAD subgroup and 97.4% for the non-CLAD subgroup. After stringent quality controls, GenCOLT gathered more than 7.3 million SNP and HLA genotypes for 387 LT pairs, including 91% pairs composed of donor and recipient of European ancestry. Overall, GenCOLT is an accurate snapshot of LT clinical practice in France and Belgium between 2009 and 2018. It currently represents one of the largest genetic biobanks dedicated to LT with data available simultaneously for donors and recipients. This unique cohort will empower to run comprehensive GWAS investigations of CLAD and other LT outcomes.

Knockdown of swine leukocyte antigen expression in porcine lung transplants enables graft survival without immunosuppression

Immune rejection remains the major obstacle to long-term survival of allogeneic lung transplants. The expression of major histocompatibility complex molecules and minor histocompatibility antigens triggers allogeneic immune responses that can lead to allograft rejection. Transplant outcomes therefore depend on long-term immunosuppression, which is associated with severe side effects. To address this problem, we investigated the effect of genetically engineered transplants with permanently down-regulated swine leukocyte antigen (SLA) expression to prevent rejection in a porcine allogeneic lung transplantation (LTx) model. Minipig donor lungs with unmodified SLA expression (control group, n = 7) or with modified SLA expression (treatment group, n = 7) were used to evaluate the effects of SLA knockdown on allograft survival and on the nature and strength of immune responses after terminating an initial 4-week period of immunosuppression after LTx. Genetic engineering to down-regulate SLA expression was achieved during ex vivo lung perfusion by lentiviral transduction of short hairpin RNAs targeting mRNAs encoding β2-microglobulin and class II transactivator. Whereas all grafts in the control group were rejected within 3 months, five of seven animals in the treatment group maintained graft survival without immunosuppression during the 2-year monitoring period. Compared with controls, SLA-silenced lung recipients had lower donor-specific antibodies and proinflammatory cytokine concentrations in the serum. Together, these data demonstrate a survival benefit of SLA-down-regulated lung transplants in the absence of immunosuppression.

Impact of Spousal Donation on Postoperative Outcomes of Living-donor Lobar Lung Transplantation

BACKGROUND

The effect of human leukocyte antigen mismatches between donors and recipients on postoperative outcomes of lung transplantation remains controversial. We retrospectively reviewed adult recipients receiving living-donor lobar lung transplantation (LDLLT) to examine the difference in de novo donor-specific antibody (dnDSA) development and clinically diagnosed unilateral chronic lung allograft dysfunction per graft (unilateral CLAD) between lung grafts donated by spouses (nonblood relatives) and nonspouses (relatives within the third degree). We also investigated the difference in prognoses between recipients undergoing LDLLTs including spouse donors (spousal LDLLTs) and not including spouse donors (nonspousal LDLLTs).

METHODS

In this study, 63 adult recipients undergoing LDLLTs (61 bilateral and 2 unilateral LDLLTs from 124 living donors) between 2008 and 2020 were enrolled. The cumulative incidence of dnDSAs per lung graft was calculated, and prognoses were compared between recipients undergoing spousal and nonspousal LDLLTs.

RESULTS

The cumulative incidence of both dnDSAs and unilateral CLAD in grafts donated by spouses was significantly higher than that in grafts donated by nonspouses (5-y incidence of dnDSAs: 18.7% versus 6.4%, P = 0.038; 5-y incidence of unilateral CLAD: 45.6% versus 19.4%, P = 0.011). However, there were no significant differences in the overall survival or chronic lung allograft dysfunction-free survival between recipients undergoing spousal and nonspousal LDLLTs ( P > 0.99 and P = 0.434, respectively).

CONCLUSIONS

Although there were no significant differences in prognoses between spousal and nonspousal LDLLTs, more attention should be paid to spousal LDLLTs because of the higher development rate of dnDSAs and unilateral CLAD.

DQA1 Eplet Mismatch Load As an Independent Risk Factor of CLAD After Lung Transplantation

Lung transplantation remains the treatment of choice for end-stage lung diseases, and recipient selection is currently based on clinical urgency, ABO compatibility, and donor size. The risk of allosensitization is classically based on HLA mismatch, but eplet mismatch load is increasingly seen to be important in long-term outcomes in solid organ transplantation. Chronic lung allograft dysfunction (CLAD) is relatively common and relevant, affecting almost 50% of patients 5 y after transplantation and being the first cause of death from the first year after transplantation. The overall class-II eplet mismatch load has been associated with CLAD development.

Methods

Based on clinical data, 240 lung transplant recipients were eligible for CLAD, and HLA and eplet mismatch was analyzed using the HLAMatchmaker 3.1 software.

Results

A total of 92 (38.3%) lung transplant recipients developed CLAD. The time free-of-CLAD was significantly decreased in patients with presence of DQA1 eplet mismatches (P = 0.015). Furthermore, when other previously described CLAD risk factors were studied in a multivariate analysis, the presence of DQA1 eplet mismatches was found to be independently associated with the early onset of CLAD.

Conclusions

The concept of epitope load has arisen as a new tool to better define donor-recipient immunologic compatibility. The presence of DQA1 eplet mismatches potentially would increase the likelihood of developing CLAD.

Risk Factors of Rejection in Renal Transplant Recipients: A Narrative Review

Multiple factors influence graft rejection after kidney transplantation. Pre-operative factors affecting graft function and survival include donor and recipient characteristics such as age, gender, race, and immunologic compatibility. In addition, several peri- and post-operative parameters affect graft function and rejection, such as cold and warm ischemia times, and post-operative immunosuppressive treatment. Exposure to non-self-human leucocyte antigens (HLAs) prior to transplantation up-regulates the recipient’s immune system. A higher rate of acute rejection is observed in transplant recipients with a history of pregnancies or significant exposure to blood products because these patients have higher panel reactive antibody (PRA) levels. Identifying these risk factors will help physicians to reduce the risk of allograft rejection, thereby promoting graft survival. In the current review, we summarize the existing literature on donor- and recipient-related risk factors of graft rejection and graft loss following kidney transplantation.

Acute Rejection in the Modern Lung Transplant Era

Acute cellular rejection (ACR) remains a common complication after lung transplantation. Mortality directly related to ACR is low and most patients respond to first-line immunosuppressive treatment. However, a subset of patients may develop refractory or recurrent ACR leading to an accelerated lung function decline and ultimately chronic lung allograft dysfunction. Infectious complications associated with the intensification of immunosuppression can also negatively impact long-term survival. In this review, we summarize the most recent evidence on the mechanisms, risk factors, diagnosis, treatment, and prognosis of ACR. We specifically focus on novel, promising biomarkers which are under investigation for their potential to improve the diagnostic performance of transbronchial biopsies. Finally, for each topic, we highlight current gaps in knowledge and areas for future research.

The impact of HLA-DR mismatch status on retransplant-free survival and bronchiolitis obliterans syndrome‒free survival among sensitized lung transplant recipients

INTRODUCTION

Donor‒recipient HLA-DR locus matching may be protective against bronchiolitis obliterans syndrome (BOS) in lung transplant recipients. It is unknown whether this benefit is more significant among sensitized (calculated panel reactive antibodies (CPRAs) of >0%) and highly sensitized (CPRAs of ≥80%) recipients who may be at a higher risk for BOS.

METHODS

This was a retrospective cohort study of adults in the Scientific Registry of Transplant Recipients who underwent lung transplantation between May 5, 2005 and May 31, 2019. Retransplant-free survival and BOS-free survival were compared among recipients with 0 vs ≥1 DR mismatches, grouped according to sensitization.

RESULTS

Among all 20,355 included recipients, 0 DR mismatch status was associated with improved retransplant-free survival (hazard ratio [HR] = 0.83, 95% CI = 0.74-0.93, p = 0.002) and BOS-free survival (HR = 0.86, 95% CI = 0.77-0.96, p = 0.007). Among sensitized recipients, 0 DR mismatch status was also associated with improved retransplant-free survival (HR = 0.79, 95% CI = 0.65-0.97, p = 0.02) and BOS-free survival (HR = 0.82, 95% CI = 0.67-1.00, p = 0.04). There was however no difference in retransplant-free or BOS-free survival between sensitized and non-sensitized recipients with 0 DR mismatches. Among highly sensitized recipients, 0 DR mismatch status was not associated with retransplant-free or BOS-free survival. Among sensitized and highly sensitized recipients, 0 DR mismatch status was not associated with reduced use of plasmapheresis or reduced biopsy-proven, treated acute cellular rejection compared with non-sensitized recipients.

CONCLUSIONS

HLA-DR matching is associated with a similar improvement in retransplant-free and BOS-free survival among non-sensitized and sensitized lung transplant recipients. DR matching does not confer a more substantial retransplant-free or BOS-free survival benefit to highly sensitized recipients than to non-sensitized recipients.

Non-HLA Abs in Solid Organ Transplantation

The role of anti-HLA antibodies in solid organ rejection is well established and these antibodies are routinely monitored both in patients in the waiting list and in the post-transplant setting. More recently, the presence of other antibodies directed towards non-HLA antigens, or the so-called minor histocompatibility antigens, has drawn the attention of the transplant community; however, their possible involvement in the graft outcome remains uncertain. These antibodies have been described to possibly have a role in rejection and allograft failure. This review focuses on the most studied non-HLA antibodies and their association with different clinical outcomes considered in solid organ transplantation with the aim of clarifying their clinical implication and potential relevance for routine testing.

Differential gene analysis during the development of obliterative bronchiolitis in a murine orthotopic lung transplantation model: A comprehensive transcriptome-based analysis

BACKGROUND

Obliterative bronchiolitis (OB) is a known issue during minor histocompatibility antigen (mHA) disparity during lung transplantation. This study evaluated gene expression in a murine orthotropic lung transplantation model using microarray analysis.

METHODS

Left lungs from C57BL/10(H-2b) donor mice were transplanted into mHA-mismatched C57BL/6(H-2b) recipient mice. Three groups (OB, non-OB, and sham controls) were confirmed pathologically and analyzed. Gene expression changes in the lung grafts were determined by microarray and immunohistochemical staining, and genes were verified by quantitative PCR in the lungs and mediastinal lymph nodes (LNs).

RESULTS

A total of 1343 genes were upregulated in the OB lungs compared to the sham group. Significant upregulation was observed for genes related to innate, e.g. Tlr2 and CCL3 and adaptive immunity, e.g. H2-ab1 and Il-21. Positive labeling for MHC class II antigen was observed in the bronchial epithelium of OB accompanied with B cells. We found increased Tlr2, Ccl3, H2-ab1, Il-21, Ighg3, Ifng, and Pdcd1 mRNA expression in the OB lung, and increased Il-21, Ighg3, and Pdcd1 expression in the OB LNs.

CONCLUSIONS

Adaptive and innate immune reactions were involved in OB after lung transplantation, and genetic examination of related genes could be used for detection of OB.

Early Identification of Chronic Lung Allograft Dysfunction: The Need of Biomarkers

A growing number of patients with end-stage lung disease have benefited from lung transplantation (LT). Improvements in organ procurement, surgical techniques and intensive care management have greatly increased short-term graft survival. However, long-term outcomes remain limited, mainly due to the onset of chronic lung allograft dysfunction (CLAD), whose diagnosis is based on permanent loss of lung function after the development of irreversible lung lesions. CLAD is associated with high mortality and morbidity, and its exact physiopathology is still only partially understood. Many researchers and clinicians have searched for CLAD biomarkers to improve diagnosis, to refine the phenotypes associated with differential prognosis and to identify early biological processes that lead to CLAD to enable an early intervention that could modify the inevitable degradation of respiratory function. Donor-specific antibodies are currently the only biomarkers used in routine clinical practice, and their significance for accurately predicting CLAD is still debated. We describe here significant studies that have highlighted potential candidates for reliable and non-invasive biomarkers of CLAD in the fields of imaging and functional monitoring, humoral immunity, cell-mediated immunity, allograft injury, airway remodeling and gene expression. Such biomarkers would improve CLAD prediction and allow differential LT management regarding CLAD risk.

Impact of human leukocyte antigen mismatch on lung transplant outcome

OBJECTIVES

Human leucocyte antigen (HLA) mismatch between donor and recipient has a differential impact on the outcome after transplant (Tx) among transplantable solid organs. Although the lung is considered a highly antigenic organ, the impact of HLA matching between the donor and the recipient has been shown to be heterogeneous on lung Tx outcome. To provide further evidence that HLA matching should be considered in the decision process prior to lung Tx, we evaluated the impact of donor/recipient HLA mismatch on the outcome after lung Tx at our institution.

METHODS

All patients who underwent lung Tx were analysed in this retrospective single-cohort study between 1994 and 2013 for HLA (-A, -B or -DR) matching between the donor and the recipient and their association with overall survival, the incidence of acute cellular rejection (ACR) and the development of chronic lung allograft dysfunction (CLAD).

RESULTS

In total, 371 (197 men) patients were included. Of these, 117 patients had no HLA match (0/6), 143 had a 1/6 match, 77 had 2/6 matches, 28 had 3/6 matches and 6 had 4/6 matches. One hundred and twenty-two (33%) patients experienced at least 1 episode of ACR and 172 (46%) patients developed CLAD. Univariate analysis showed a significant correlation between HLA mismatch and the development of CLAD, whereas multivariate analysis revealed that the number of HLA matches (hazard ratio 0.76; P = 0.002), antibodies to cytomegalovirus in either donors or recipients (hazard ratio 1.52; P = 0.036) and donor age (hazard ratio 1.03; P < 0.001) were independent risk factors for the development of CLAD. On the other hand, HLA matches did not correlate with the incidence of ACR and with the overall survival rate.

CONCLUSIONS

The number of HLA mismatches between donors and recipients after lung Tx did not correlate with ACR or with the overall survival. In contrast, HLA mismatch correlated with the development of CLAD and should therefore be considered a risk factor.

Lung Injury and Loss of Regulatory T Cells Primes for Lung-Restricted Autoimmunity

Lung transplantation is a life-saving therapy for several end-stage lung diseases. However, lung allografts suffer from the lowest survival rate predominantly due to rejection. The pathogenesis of alloimmunity and its role in allograft rejection has been extensively studied and multiple approaches have been described to induce tolerance. However, in the context of lung transplantation, dysregulation of mechanisms, which maintain tolerance against self-antigens, can lead to lung-restricted autoimmunity, which has been recently identified to drive the immunopathogenesis of allograft rejection. Indeed, both preexisting as well as de novo lung-restricted autoimmunity can play a major role in the development of lung allograft rejection. The three most widely studied lung-restricted self-antigens include collagen type I, collagen type V, and k-alpha 1 tubulin. In this review, we discuss the role of lung-restricted autoimmunity in the development of both early as well as late lung allograft rejection and recent literature providing insight into the development of lung-restricted autoimmunity through the dysfunction of immune mechanisms which maintain peripheral tolerance.

Specific Donor HLA-DR Types Correlate With Altered Susceptibility to Development of Chronic Lung Allograft Dysfunction

BACKGROUND

The greatest challenge to long-term graft survival is the development of chronic lung allograft dysfunction. Th17 responses to collagen type V (colV) predispose lung transplant patients to the severe obstructive form of chronic lung allograft dysfunction, known as bronchiolitis obliterans syndrome (BOS). In a previous study cohort (n = 54), pretransplant colV responses were increased in recipients expressing HLA-DR15, consistent with the high binding avidity of colV (α1) peptides for HLA-DR15, whereas BOS incidence, which was known to be strongly associated with posttransplant autoimmunity to colV, was higher in patients who themselves lacked HLA-DR15, but whose lung donor expressed it.

METHODS

To determine if this DR-restricted effect on BOS incidence could be validated in a larger cohort, we performed a retrospective analysis of outcomes for 351 lung transplant recipients transplanted between 1988 and 2008 at the University of Wisconsin. All subjects were followed until graft loss, death, loss to follow-up, or through 2014, with an average follow-up of 7 years. Comparisons were made between recipients who did or did not develop BOS. Grading of BOS followed the recommendations of the international society for heart and lung transplantation.

RESULTS

Donor HLA-DR15 was indeed associated with increased susceptibility to severe BOS in this population. We also discovered that HLA-DR7 expression by the donor or HLA-DR17 expression by the recipient decreased susceptibility.

CONCLUSIONS

We show in this retrospective study that specific donor HLA class II types are important in lung transplantation, because they are associated with either protection from or susceptibility to development of severe BOS.

Pre-transplant Panel Reactive Antibody and Survival in Adult Cystic Fibrosis Patients After Lung Transplantation

BACKGROUND

Survival implications of pre-transplant antibodies to human leukocyte antigens prior to lung transplantation (LTx) in adult cystic fibrosis (CF) patients are unknown.

METHODS

Data from the United Network for Organ Sharing Registry (1987-2013) were used to compare survival differences in adult CF patients with pre-transplant class I and II panel reactive antibody (PRA) levels ≤10 versus >10 %.

RESULTS

Of 3149 CF LTx recipients, 1526 and 1399 were included in univariate survival analyses of class I and II PRA, respectively, while 1106 and 1001 were included in multivariate Cox analyses for class I and class II, respectively. Kaplan-Meier survival functions failed to demonstrate significant differences in survival with PRA >10 % for class I (Log-rank test: χ (2) (df = 1): 1.11, p = 0.293) or class II (Log-rank test: χ (2) (df = 1): 0.99, p = 0.320). Adjusting for covariates, multivariate Cox models demonstrated that class II PRA >10 % was associated with a significant increase in mortality hazard (HR 1.918; 95 % CI 1.128, 3.261; p = 0.016), whereas class I PRA >10 % was uncorrelated with this outcome.

CONCLUSIONS

Pre-transplant PRA class II >10 % in adult CF patients is associated with elevated mortality hazard after LTx.

Current methods and challenges in the comprehensive characterization of human pluripotent stem cells

Pluripotent stem cells (PSCs) are powerful tools for basic scientific research and promising agents for drug discovery and regenerative medicine. Technological advances have made it increasingly easy to generate PSCs but the various lines generated may differ in their characteristics based on their origin, derivation, number of passages, and culture conditions. In order to confirm the pluripotency, quality, identity, and safety of pluripotent cell lines as they are derived and maintained, it is critical to perform a panel of characterization assays. Functional pluripotency is determined using tests that rely on the expression of specific markers in the undifferentiated and differentiated states; tests for quality, identity and safety are less specialized. This article provides a comprehensive review of current practices in PSC characterization and explores challenges in the field, from the selection of markers to the development of simple and scalable methods. It also delves into emerging trends like the adoption of alternative assays that could be used to supplement or replace traditional methods, specifically the use of in silico assays for determining pluripotency.

Influence of human leukocyte antigen mismatching on bronchiolitis obliterans syndrome in lung transplantation

BACKGROUND

Varying results have been reported in the investigation of human leukocyte antigen (HLA) mismatching and bronchiolitis obliterans syndrome (BOS) after lung transplantation (LTx).

METHODS

The UNOS database was queried for the period 1997 to 2013 to examine HLA mismatching and its association with BOS in LTx.

RESULTS

Of 16,959 first-time adult LTx recipients, 16,854 were included in the univariate Cox analysis and Kaplan-Meier survival function evaluation, and 14,578 were included in multivariate Cox models. Multivariate Cox analysis showed that the number of total HLA mismatches was significantly associated with greater hazard of BOS (HR = 1.060; 95% CI 1.013 to 1.108; p = 0.011), as was the presence of 2 HLA-A mismatches, when compared with 0 or 1 mismatch at that locus (HR = 1.128; 95% CI 1.026 to 1.240; p = 0.012). These results were confirmed using competing-risks regression models that adjusted for death before BOS diagnosis. Multivariate Cox models identified no significant association with BOS hazard for HLA-B (HR = 1.014; 95% CI 0.914 to 1.126; p = 0.785) or HLA-DR (HR = 1.085; 95% CI 0.987 to 1.193; p = 0.090) mismatches. Higher body mass index was associated with increased risk for BOS, whereas older age was protective against BOS. Induction with alemtuzumab (HR = 0.343; 95% CI 0.252 to 0.467; p < 0.001) or basiliximab (HR = 0.862; 95% CI 0.758 to 0.980; p = 0.023) and longer ischemic time (HR = 0.909; 95% CI 0.877 to 0.942; p < 0.001) were associated with lower hazard of BOS.

CONCLUSIONS

Total HLA mismatches are associated with increased risk for BOS, specifically at the A locus. Induction with alemtuzumab or basiliximab reduced the risk, whereas greater ischemic time appears to also be protective.

Human leukocyte antigen mismatching and survival after lung transplantation in adult and pediatric patients with cystic fibrosis

INTRODUCTION

The influence of human leukocyte antigen (HLA) mismatching on survival in adult and pediatric patients with cystic fibrosis (CF) after lung transplantation (LTx) is unknown.

METHODS

The United Network for Organ Sharing database was queried from 1987 to 2013 to determine the influence of HLA mismatching on survival in adult and pediatric CF LTx recipients by assessing the association of HLA mismatching with survival in first-time adult (aged ≥ 18 years) and pediatric (aged <18 years) recipients.

RESULTS

Of 3149 adult and 489 pediatric patients with CF, 3145 and 489 were used for univariate Cox analysis, 2687 and 363 for Kaplan-Meier survival analysis, and 2073 and 257 for multivariate Cox analysis, respectively. Univariate analyses in adult and pediatric patients with CF demonstrated conflicting associations between HLA mismatching and survival (adult hazard ratio [HR], 1.0; 95% confidence interval [CI], 0.97-1.1; P = .45 vs pediatric HR, 0.87; 95% CI, 0.77-0.99; P = .032). Multivariate Cox models including both pediatric and adult patients confirmed that HLA mismatching had an initially protective effect at young ages (HR, 0.85; 95% CI, 0.73-0.99; P = .044) and that this protective effect diminished at older ages and was no longer associated with survival at P < .05 beyond age 10 years.

CONCLUSIONS

HLA mismatching has significantly different implications for survival after LTx in adult compared with pediatric patients with CF.

Donor-specific antibodies are associated with antibody-mediated rejection, acute cellular rejection, bronchiolitis obliterans syndrome, and cystic fibrosis after lung transplantation

BACKGROUND

Lung transplantation is limited by chronic lung allograft dysfunction. Acute cellular rejection (ACR) is a risk factor for allograft dysfunction; however, the role of antibody-mediated rejection (AMR) is not well characterized.

METHODS

This was a retrospective review from 2007 to 2011 of lung transplant recipients with human leukocyte antigen (HLA) antibody testing using Luminex (Luminex Corp, Austin, TX) single-antigen beads. Statistics included Fisher's exact test for significance.

RESULTS

Donor-specific antibodies (DSA) developed in 13 of 44 patients. Of the 13 with DSA, 12 had cystic fibrosis compared with 18 of 31 in the non-DSA group (p = 0.035). Of those with DSAs, 23.1% occurred within the first year, and 69.2% occurred between 1 and 3 years. Twelve of 13 DSA patients had anti-HLA DQ specificity compared with 2 of 31 non-DSA patients (p = 0.0007). AMR developed in 10 of the 13 DSA patients compared with 1 of 31 non-DSA patients (p = 0.0001). The DSA group experienced 2.6 episodes/patient of cellular rejection vs 1.7 episodes/patient in the non-DSA group (p = 0.059). Bronchiolitis obliterans syndrome developed in 11 of 13 in the DSA group vs 10 of 31 in the non-DSA group (p = 0.0024). In the DSA group, 11.5% HLAs matched compared with 20.4% in the non-DSA group (p = 0.093). AMR developed in 11 of 22 patients in the non-DSA HLA group compared with 0 of 22 in the group without non-DSA HLA antibodies (p = 0.002). Survival at 1 and 3 years was 92% and 36% in the DSA group, respectively, and 97% and 65% in the non-DSA group.

CONCLUSIONS

DSAs and non-DSAs occur frequently after lung transplantation. DSAs are prevalent in the cystic fibrosis population and are associated with AMR, bronchiolitis obliterans syndrome, and possibly, ACR.

From gut to kidney: transporting and metabolizing calcineurin-inhibitors in solid organ transplantation

Since their introduction circa 35 years ago, calcineurin-inhibitors (CNI) have become the cornerstone of immunosuppressive therapy in solid organ transplantation. However, CNI's possess a narrow therapeutic index with potential severe consequences of drug under- or overexposure. This demands a meticulous policy of Therapeutic Drug Monitoring (TDM) to optimize outcome. In clinical practice optimal dosing is difficult to achieve due to important inter- and intraindividual variation in CNI pharmacokinetics. A complex and often interdependent set of factors appears relevant in determining drug exposure. These include recipient characteristics such as age, race, body composition, organ function, and food intake, but also graft-related characteristics such as: size, donor-age, and time after transplantation can be important. Fundamental (in vitro) and clinical studies have pointed out the intrinsic relation between the aforementioned variables and the functional capacity of enzymes and transporters involved in CNI metabolism, primarily located in intestine, liver and kidney. Commonly occurring polymorphisms in genes responsible for CNI metabolism (CYP3A4, CYP3A5, CYP3A7, PXR, POR, ABCB1 (P-gp) and possibly UGT) are able to explain an important part of interindividual variability. In particular, a highly prevalent SNP in CYP3A5 has proven to be an important determinant of CNI dose requirements and drug-dose-interactions. In addition, a discrepancy in genotype between graft and receptor has to be taken into account. Furthermore, common phenomena in solid organ transplantation such as inflammation, ischemia- reperfusion injury, graft function, co-medication, altered food intake and intestinal motility can have a differential effect on the expression enzymes and transporters involved in CNI metabolism. Notwithstanding the built-up knowledge, predicting individual CNI pharmacokinetics and dose requirements on the basis of current clinical and experimental data remains a challenge.

Impact of HLA matching and HLA antibodies in organ transplantation: a collaborative transplant study view

The Collaborative Transplant Study (CTS) was initiated in 1982 in Heidelberg, Germany, and originated from the need to gain further insight into the complex problems and risks involved in human organ transplantation. Currently, more than 400 transplant centers in 45 countries are contributing to this voluntary international effort, and from the beginning of the study, the impact on graft outcome of immunological factors, such as matching for HLA antigens and allosensitization to HLA and non-HLA antigens, have been areas of interest. Herein, we summarize the recent findings from the CTS on these two topics.

Chronic allograft dysfunction

Chronic, progressive, and irreversible loss of lung function is the major medium-term and long-term complication after lung transplantation and the leading cause of death. Over the past decade, progress has been made in understanding the pathogenesis of bronchiolitis obliterans. Alloimmune factors and nonalloimmune factors may contribute to its development. Understanding the precise mechanism of each type of chronic allograft dysfunction may open up the field for new preventive and therapeutic interventions. This article reviews major new insights into the clinical aspects, pathophysiology, risk factors, diagnosis, and management of chronic allograft dysfunction after lung transplantation.