Lung Innate Lymphoid Cell Composition Is Altered in Primary Graft Dysfunction

Rationale: Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation, but the immunologic mechanisms are poorly understood. Innate lymphoid cells (ILC) are a heterogeneous family of immune cells regulating pathologic inflammation and beneficial tissue repair. However, whether changes in donor-derived lung ILC populations are associated with PGD development has never been examined.Objectives: To determine whether PGD in chronic obstructive pulmonary disease or interstitial lung disease transplant recipients is associated with alterations in ILC subset composition within the allograft.Methods: We performed a single-center cohort study of lung transplantation patients with surgical biopsies of donor tissue taken before, and immediately after, allograft reperfusion. Donor immune cells from 18 patients were characterized phenotypically by flow cytometry for single-cell resolution of distinct ILC subsets. Changes in the percentage of ILC subsets with reperfusion or PGD (grade 3 within 72 h) were assessed.Measurements and Main Results: Allograft reperfusion resulted in significantly decreased frequencies of natural killer cells and a trend toward reduced ILC populations, regardless of diagnosis (interstitial lung disease or chronic obstructive pulmonary disease). Seven patients developed PGD (38.9%), and PGD development was associated with selective reduction of the ILC2 subset after reperfusion. Conversely, patients without PGD exhibited significantly higher ILC1 frequencies before reperfusion, accompanied by elevated ILC2 frequencies after allograft reperfusion.Conclusions: The composition of donor ILC subsets is altered after allograft reperfusion and is associated with PGD development, suggesting that ILCs may be involved in regulating lung injury in lung transplant recipients.

Discharge frailty following lung transplantation

INTRODUCTION

Frailty at listing for lung transplant has been associated with waitlist and post-transplant mortality. Frailty trajectories following transplant, however, have been less well characterized, including whether recipient frailty improves. The objective of this study was to identify prevalence and risk factors for frailty at discharge and to evaluate changes in frail recipients enrolled in an outpatient physical therapy program.

METHODS

This was a single-center prospective cohort study of lung transplant recipients. Enrollees completed a short physical performance battery (SPPB) to assess frailty at listing and at initial hospital discharge.

RESULTS

Of the 111 enrolled recipients, none were frail at listing and 18 (16.2%) were prefrail. At discharge, however, 60 (54.1%) patients were frail. Discharge frailty was associated with prefrailty at listing, acute kidney injury post-transplant, and longer intensive care unit stay. Among the 35 patients who were frail at discharge and who were enrolled in an outpatient PT program, the median improvement in SPPB was 6 points (IQR = 5-7 points), and 85.7% became not frail over a median of 6 weeks.

CONCLUSION

Discharge frailty is common following lung transplantation. In most frail patients, an intensive outpatient physical therapy program is associated with improvement in frailty, as assessed by the SPPB.

The association of post-lung transplant acute kidney injury with mortality is independent of primary graft dysfunction: A cohort study

BACKGROUND

Prior studies of post-lung transplant acute kidney injury (AKI) have not accounted for confounding effects of primary graft dysfunction (PGD). We sought to test the impact of PGD on AKI risk factors and on the association of AKI with mortality.

METHODS

We included patients transplanted at the University of Pennsylvania from 2005-12, defined AKI using consensus criteria during transplant hospitalization, and defined PGD as grade 3 at 48-72 hours. We used multivariable logistic regression to test the impact of PGD on AKI risk factors and Cox models to test association of AKI with one-year mortality adjusting for PGD and other confounders.

RESULTS

Of 299 patients, 188 (62.9%) developed AKI with 142 (75%) cases occurring by postoperative day 4. In multivariable models, PGD was strongly associated with AKI (OR 3.76, 95% CI 1.72-8.19, P = .001) but minimally changed associations of other risk factors with AKI. Both AKI (HR 3.64, 95% CI 1.68-7.88, P = .001) and PGD (HR 2.55, 95% CI 1.40-4.64, P = .002) were independently associated with one-year mortality.

CONCLUSIONS

Post-lung transplant AKI risk factors and association of AKI with mortality were independent of PGD. AKI may therefore be a target for improving lung transplant mortality rather than simply an epiphenomenon of PGD.

Postreperfusion plasma endothelial activation markers are associated with acute kidney injury after lung transplantation

Acute kidney injury (AKI) is common after lung transplantation, but molecular markers remain poorly studied. The endothelial activation markers soluble thrombomodulin (sTM), protein C, and plasminogen activator inhibitor-1 (PAI-1) are implicated in kidney microcirculatory injury in animal models of AKI. We tested the association of 6-hour postreperfusion plasma levels of these markers with posttransplant AKI severity in patients enrolled in the Lung Transplant Outcomes Group prospective cohort study at the University of Pennsylvania during two eras: 2004-06 (n = 61) and 2013-15 (n = 67). We defined AKI stage through postoperative day 5 using Kidney Disease Improving Global Outcomes creatinine criteria. We used multivariable ordinal logistic regression to determine the association of each biomarker with AKI, adjusted for primary graft dysfunction and extracorporeal life support. AKI occurred in 57 (45%) patients across both eras: 28 (22%) stage 1, 29 (23%) stage 2-3. Higher sTM and lower protein C plasma levels were associated with AKI stage in each era and remained so in multivariable models utilizing both eras (sTM: OR 1.76 [95% CI 1.19-2.60] per standard deviation, P = .005; protein C: OR 0.54 [1.19-2.60], P = .003). We conclude that 6-hour postreperfusion plasma sTM and protein C levels are associated with early postlung transplant AKI severity.

Collagen type-V is a danger signal associated with primary graft dysfunction in lung transplantation

BACKGROUND

Primary graft dysfunction (PGD) is the leading cause of early mortality after lung transplantation. Anti-collagen type-V (col(V)) immunity has been observed in animal models of ischemia-reperfusion injury (IRI) and in PGD. We hypothesized that collagen type-V is an innate danger signal contributing to PGD pathogenesis.

METHODS

Anti-col(V) antibody production was detected by flow cytometric assay following cultures of murine CD19+ splenic cells with col.(V). Responding murine B cells were phenotyped using surface markers. RNA-Seq analysis was performed on murine CD19+ cells. Levels of anti-col(V) antibodies were measured in 188 recipients from the Lung Transplant Outcomes Group (LTOG) after transplantation.

RESULTS

Col(V) induced rapid production of anti-col(V) antibodies from murine CD19+ B cells. Subtype analysis demonstrated innate B-1 B cells bound col.(V). Col(V) induced a specific transcriptional signature in CD19+ B cells with similarities to, yet distinct from, B cell receptor (BCR) stimulation. Rapid de novo production of anti-col(V) Abs was associated with an increased incidence of clinical PGD after lung transplant.

CONCLUSIONS

This study demonstrated that col.(V) is an rapidly recognized by B cells and has specific transcriptional signature. In lung transplants recipients the rapid seroconversion to anti-col(V) Ab is linked to increased risk of grade 3 PGD.

An Ethical Framework for the Care of Patients with Prolonged Hospitalization Following Lung Transplantation

The lung allocation score system in the United States and several European countries gives more weight to risk of death without transplantation than to survival following transplantation. As a result, centers transplant sicker patients, leading to increased length of initial hospitalization. The care of patients who have accumulated functional deficits or additional organ dysfunction during their prolonged stay can be ethically complex. Disagreement occurs between the transplant team, patients and families, and non-transplant health care professionals over the burdens of ongoing intensive intervention. These cases highlight important ethical issues in organ transplantation, including the nature and requirements of transplant informed consent, the limits of physician prognostication, patient autonomy and decision-making capacity following transplant, obligations to organ donors and to other potential recipients, and the impact of program metrics on individualized recipient care. We outline general ethical principles for the care of lung transplant recipients with prolonged hospitalization and give regulatory, research, and patient-centered recommendations for these cases.

The seizure onset zone drives state-dependent epileptiform activity in susceptible brain regions

OBJECTIVE

Due to variability in the patterns of propagation of interictal epileptiform discharges (IEDs), qualitative definition of the irritative zone has been challenging. Here, we introduce a quantitative approach toward exploration of the dynamics of IED propagation within the irritative zone.

METHODS

We examined intracranial EEG (iEEG) in nine participants undergoing invasive monitoring for seizure localization. We used an automated IED detector and a community detection algorithm to identify populations of electrodes exhibiting IED activity that co-occur in time, and to group these electrodes into communities.

RESULTS

Within our algorithmically-identified communities, IED activity in the seizure onset zone (SOZ) tended to lead IED activity in other functionally coupled brain regions. The tendency of pathological activity to arise in the SOZ, and to spread to non-SOZ tissues, was greater in the asleep state.

CONCLUSIONS

IED activity, and, by extension, the variability observed between the asleep and awake states, is propagated from a core seizure focus to nearby less pathological brain regions.

SIGNIFICANCE

Using an unsupervised, computational approach, we show that the spread of IED activity through the epilepsy network varies with physiologic state.

Molecular analysis of the endobronchial stent microbial biofilm reveals bacterial communities that associate with stent material and frequent fungal constituents

Endobronchial stents are increasingly used to treat airway complications in multiple conditions including lung transplantation but little is known about the biofilms that form on these devices. We applied deep sequencing to profile luminal biofilms of 46 endobronchial stents removed from 20 subjects primarily with lung transplantation-associated airway compromise. Microbial communities were analyzed by bacterial 16S rRNA and fungal ITS marker gene sequencing. Corynebacterium was the most common bacterial taxa across biofilm communities. Clustering analysis revealed three bacterial biofilm types: one low diversity and dominated by Corynebacterium; another was polymicrobial and characterized by Staphylococcus; and the third was polymicrobial and associated with Pseudomonas, Streptococcus, and Prevotella. Biofilm type was significantly correlated with stent material: covered metal with the Staphylococcus-type biofilm, silicone with the Corynebacterium-dominated biofilm, and uncovered metal with the polymicrobial biofilm. Subjects with sequential stents had frequent transitions between community types. Fungal analysis found Candida was most prevalent, Aspergillus was common and highly enriched in two of three stents associated with airway anastomotic dehiscence, and fungal taxa not typically considered pathogens were highly enriched in some stents. Thus, molecular analysis revealed a complex and dynamic endobronchial stent biofilm with three bacterial types that associate with stent material, a central role for Corynebacterium, and that both expected and unexpected fungi inhabit this unique niche. The current work provides a foundation for studies to investigate the relationship between stent biofilm composition and clinical outcomes, mechanisms of biofilm establishment, and strategies for improved stent technology and use in airway compromise.

Lung Transplantation

Lung transplantation is an appropriate therapeutic option for select patients with end-stage lung diseases and offers the possibility of improved quality of life and longer survival. Unfortunately, the transplant recipient is at risk for numerous immunologic, infectious, and medical complications that threaten both of these goals. Median survival after lung transplantation is approximately 6 years. Optimizing outcomes requires close partnership between the patient, transplant center, and primary medical team. Early referral to a transplant center should be considered for patients with idiopathic pulmonary fibrosis and related interstitial lung diseases due to risk of acute exacerbation and accelerated development of respiratory failure.

Quantitative Evidence for Revising the Definition of Primary Graft Dysfunction after Lung Transplant

RATIONALE

Primary graft dysfunction (PGD) is a form of acute lung injury that occurs after lung transplantation. The definition of PGD was standardized in 2005. Since that time, clinical practice has evolved, and this definition is increasingly used as a primary endpoint for clinical trials; therefore, validation is warranted.

OBJECTIVES

We sought to determine whether refinements to the 2005 consensus definition could further improve construct validity.

METHODS

Data from the Lung Transplant Outcomes Group multicenter cohort were used to compare variations on the PGD definition, including alternate oxygenation thresholds, inclusion of additional severity groups, and effects of procedure type and mechanical ventilation. Convergent and divergent validity were compared for mortality prediction and concurrent lung injury biomarker discrimination.

MEASUREMENTS AND MAIN RESULTS

A total of 1,179 subjects from 10 centers were enrolled from 2007 to 2012. Median length of follow-up was 4 years (interquartile range = 2.4-5.9). No mortality differences were noted between no PGD (grade 0) and mild PGD (grade 1). Significantly better mortality discrimination was evident for all definitions using later time points (48, 72, or 48-72 hours; P < 0.001). Biomarker divergent discrimination was superior when collapsing grades 0 and 1. Additional severity grades, use of mechanical ventilation, and transplant procedure type had minimal or no effect on mortality or biomarker discrimination.

CONCLUSIONS

The PGD consensus definition can be simplified by combining lower PGD grades. Construct validity of grading was present regardless of transplant procedure type or use of mechanical ventilation. Additional severity categories had minimal impact on mortality or biomarker discrimination.

Pulmonary arterial hypertension in adults with systemic right ventricles referred for cardiac transplantation

BACKGROUND

Systemic right ventricular (RV) failure may progress necessitating referral for orthotropic heart transplantation (OHT). Pulmonary hypertension (PH) frequently coexists in adult congenital heart disease and can complicate the assessment for OHT.

METHODS

Single-center case series of six patients (median age 34.9 years [IQR, 31.9-42.4]) with systemic RV physiology with PH referred for OHT evaluation from 2008 to 2017.

RESULTS

One-third (n = 6) of 18 patients with systemic RV physiology referred for OHT evaluation had pulmonary arterial hypertension (PAH) defined as mean pulmonary artery pressure (mPAP) > 25 mm Hg and pulmonary vascular resistance (PVR) > 3 Wood Units. Two of the six patients were considered OHT-ineligible due to PH and comorbidities. Of the remaining four, two had pre-capillary PH and underwent heart-lung transplant (HLTx). The other two demonstrated reversibility of PVR with vasodilator testing and underwent OHT alone, one of whom died post-transplant from PH crisis.

CONCLUSIONS

Pulmonary arterial hypertension is common in systemic RV patients referred for OHT. Systemic RV dysfunction places these patients at risk for post-capillary PH but pre-capillary PH can exist. Despite management with selective pulmonary vasodilators and afterload reduction, criteria for listing patients for HLTx vs OHT are not known and need further elucidation.

Donor Lung Sequence Number and Survival after Lung Transplantation in the United States

RATIONALE

In the United States, an algorithm known as the "match-run" creates an ordered ranking of potential recipients for available lung allografts. A potential recipient's match-run position, or "sequence number," is available to the transplant center when contacted with a lung offer. Lung offers with higher sequence numbers may be interpreted as a crowd-sourced evaluation of poor organ quality, though the association between the sequence number at which a lung is accepted and its recipient's post-transplant outcomes is unclear.

OBJECTIVES

We sought to evaluate the primary reasons provided when a lung offer was refused by a transplant center, transplant center and donor/organ factors associated with a higher sequence number at acceptance, and the association of the sequence number at acceptance with post-transplant mortality and graft failure.

METHODS

Match-run outcomes for lung offers that occurred in the United States from May 2007 through June 2014 were merged with recipient follow-up data through December 2017. Associations between the sequence number at the time of acceptance and selected transplant center and donor characteristics were estimated using multivariable logistic and multinomial regression models. The associations between the final sequence number and recipient survival and graft survival were estimated using multivariable time-to-event models.

RESULTS

Of 10,981 lung offer acceptances, nearly 70% were accepted by one of the top 10 ranked candidates. Higher median annual center volume and potential indicators of organ quality (e.g., abnormal chest radiograph or bronchoscopy) were associated with a higher sequence number at acceptance. There was weak evidence for a small positive relationship between the sequence number at acceptance and both mortality and graft failure. For example, the unadjusted and adjusted hazard ratios for death associated with the log-sequence number at acceptance were 1.019 (95% confidence interval, 1.001-1.038) and 1.011 (95% confidence interval, 0.989-1.033), respectively. On the absolute scale, using the multivariable model, a 10-fold increase in the sequence number translated into a 0.8% absolute decline in the predicted 5-year survival.

CONCLUSIONS

Acceptance of a donor lung offer at a later point in the match-run was associated with measurable indicators of organ quality, but not with clinically meaningful differences in post-transplant mortality or graft failure.

In-hospital and subsequent mortality among lung transplant recipients with a prolonged initial hospitalization

The care of lung transplant recipients with prolonged index hospitalizations can be ethically complex, with conflicts arising over whether the expected outcomes justify ongoing intensive interventions. There are limited data to guide these conversations. The objective of this study was to evaluate survival to discharge for lung transplant recipients based on length of stay (LOS). This was a retrospective cohort study of adult lung transplant recipients in the Scientific Registry of Transplant Recipients. For each day of the index hospitalization the mortality rate among patients who survived to that length of stay or longer was calculated. Post-discharge survival was compared in those with and without a prolonged hospitalization (defined as the 97th percentile [>90 days]). Among the 19 250 included recipients, the index hospitalization mortality was 5.4%. Posttransplant stroke and need for dialysis were the strongest predictors of index hospitalization mortality. No individual or combination of available risk factors, however, was associated with inpatient mortality consistently above 50%. Recipients with >90 day index hospitalization had a 28.8% subsequent inpatient mortality. Their 1, 3 and 5 year survival following discharge was 53%, 26%, and 16%. These data provide additional context to goals of care conversations for transplant recipients with prolonged index hospitalizations.

Presentation and Outcomes After Medical and Surgical Treatment Versus Medical Treatment Alone of Spontaneous Infectious Spondylodiscitis: A Systematic Literature Review and Meta-Analysis

STUDY DESIGN

Systematic literature review.

OBJECTIVES

The aims of this study were to (1) describe the clinical features, disabilities, and incidence of neurologic deficits of pyogenic spondylodiscitis prior to treatment and (2) compare the functional outcomes between patients who underwent medical treatment alone or in combination with surgery for pyogenic spondylodiscitis.

METHODS

A systematic literature review was performed using PubMed according to PRISMA guidelines. No year restriction was put in place. Statistical analysis of pooled data, when documented in the original report (ie, number of patients with desired variable and number of patients evaluated), was conducted to determine the most common presenting symptoms, incidence of pre- and postoperative neurologic deficits, associated comorbidities, infectious pathogens, approach for surgery when performed, and duration of hospitalization. Outcomes data, including return to work status, resolution of back pain, and functional recovery were also pooled among all studies and surgery-specific studies alone. Meta-analysis of studies with subgroup analysis of pain-free outcome in surgical and medical patients was performed.

RESULTS

Fifty of 1286 studies were included, comprising 4173 patients undergoing either medical treatment alone or in combination with surgery. Back pain was the most common presenting symptom, reported in 91% of patients. Neurologic deficit was noted in 31% of patients. Staphylococcus aureus was the most commonly reported pathogen, seen in 35% of reported cases. Decompression and fusion was the most commonly reported surgical procedure, performed in 80% of the surgically treated patients. Combined anterior-posterior procedures and staged surgeries were performed in 33% and 26% of surgeries, respectively. The meta-analysis comparing visual analog scale score at follow-up was superior among patients receiving surgery over medical treatment alone (mean difference -0.61, CI -0.90 to -0.25), while meta-analysis comparing freedom from pain in patients receiving medical treatment alone versus combined medical and surgical treatment demonstrated superior pain-free outcomes among surgical series (odds ratio 5.35, CI 2.27-12.60, P < .001), but was subject to heterogeneity among studies (I ² = 56%, P = .13). Among all patients, freedom from pain was achieved in 79% of patients, and an excellent outcome was achieved in 73% of patients.

CONCLUSION

Medical management remains first-line treatment of infectious pyogenic spondylodiscitis. Surgery may be indicated for progressive pain, persistent infection on imaging, deformity or neurologic deficits. If surgery is required, reported literature shows potential for significant pain reduction, improved neurologic function and a high number of patients returning to a normal functional/work status.

Frailty phenotypes and mortality after lung transplantation: A prospective cohort study

Frailty is associated with increased mortality among lung transplant candidates. We sought to determine the association between frailty, as measured by the Short Physical Performance Battery (SPPB), and mortality after lung transplantation. In a multicenter prospective cohort study of adults who underwent lung transplantation, preoperative frailty was assessed with the SPPB (n = 318) and, in a secondary analysis, the Fried Frailty Phenotype (FFP; n = 299). We tested the association between preoperative frailty and mortality following lung transplantation with propensity score-adjusted Cox models. We calculated postestimation marginalized standardized risks for 1-year mortality by frailty status using multivariate logistic regression. SPPB frailty was associated with an increased risk of both 1- and 4-year mortality (adjusted hazard ratio [aHR]: 7.5; 95% confidence interval [CI]: 1.6-36.0 and aHR 3.8; 95%CI: 1.8-8.0, respectively). Each 1-point worsening in SPPB was associated with a 20% increased risk of death (aHR: 1.20; 95%CI: 1.08-1.33). Frail subjects had an absolute increased risk of death within the first year after transplantation of 12.2% (95%CI: 3.1%-21%). In secondary analyses, FFP frailty was associated with increased risk of death within the first postoperative year (aHR: 3.8; 95%CI: 1.1-13.2) but not over longer follow-up. Preoperative frailty is associated with an increased risk of death after lung transplantation.

Sensitization in Transplantation: Assessment of Risk (STAR) 2017 Working Group Meeting Report

The presence of preexisting (memory) or de novo donor-specific HLA antibodies (DSAs) is a known barrier to successful long-term organ transplantation. Yet, despite the fact that laboratory tools and our understanding of histocompatibility have advanced significantly in recent years, the criteria to define presence of a DSA and assign a level of risk for a given DSA vary markedly between centers. A collaborative effort between the American Society for Histocompatibility and Immunogenetics and the American Society of Transplantation provided the logistical support for generating a dedicated multidisciplinary working group, which included experts in histocompatibility as well as kidney, liver, heart, and lung transplantation. The goals were to perform a critical review of biologically driven, state-of-the-art, clinical diagnostics literature and to provide clinical practice recommendations based on expert assessment of quality and strength of evidence. The results of the Sensitization in Transplantation: Assessment of Risk (STAR) meeting are summarized here, providing recommendations on the definition and utilization of HLA diagnostic testing, and a framework for clinical assessment of risk for a memory or a primary alloimmune response. The definitions, recommendations, risk framework, and highlighted gaps in knowledge are intended to spur research that will inform the next STAR Working Group meeting in 2019.

Obesity-driven IL-18 inhibits the suppressive function of FOXP3+ T-regulatory (Treg) cells

We investigated ways by which obesity affects the immune system and promotes inflammation, given that obesity has a high economic and medical impact, worldwide. IL-18 was the only inflammatory marker differing between our colonies of “obese but otherwise healthy” (hHFD) and “obese with low-grade inflammation” (iHFD) mice. All mice gained weight equally, had signs of low-grade inflammation (increased TNF-a, IL-1b and IL-6 mRNA) in adipose tissues, and high plasma leptin levels. The livers of hHFD mice had no inflammatory phenotype despite evidence of steatosis, whereas livers of iHFD mice had increased TNF-a, IL-1b, IL-6 and IL-7 mRNA. Levels of IL-18 were increased in livers and fat of iHFD, but not hHFD mice, and were associated with significant impairment of Treg suppressive function. Addition of IL-18 had significant inhibitory effects on the suppressive function of murine and human Tregs, and Tregs isolated from obese/overweight patients also had impaired suppressive activity. Human Tregs express high levels of IL-18Ra, and downregulate FOXP3 protein but not mRNA, when stimulated in the presence of IL-18. FOXP3 downregulation compromises the FOXP3-regulated gene network, leading to re-activation of pro-inflammatory genes such as IFN-g, IL-2, IL-6 and IL-17, and downregulation of CTLA-4 protein, which is critical for suppressive function. Our preliminary data indicate that IL-18 activates the MyD88 pathway in Tregs and impairs FOXP3 protein stability, possibly by ubiquitination and proteasomal degradation. This may be a physiologically essential tool to dampen Treg function during acute infection and increase the efficiency of immune responses, but has a detrimental effect in obesity-driven low-grade inflammation.

Primary Graft Dysfunction (PGD) Following Lung Transplantation

Primary graft dysfunction (PGD) is a form of acute lung injury that results from ischemia reperfusion injury (IRI) and is the major cause of early posttransplant morbidity and mortality. Patients who survive PGD have decreased quality of life, an increased risk of chronic lung allograft dysfunction, specifically bronchiolitis obliterans syndrome, and a significantly increased risk of death. In 2017, the International Society for Heart and Lung Transplantation released updated consensus statements on the PGD definition, most up-to-date PGD risk factors, mechanisms of PGD development, and the state-of-the-art for PGD therapeutics. Risk factor identification has led to the development of PGD predictive algorithms, although their clinical utility remains limited. Ongoing areas of controversy and discussion include further refinements to the PGD grading scheme to account for technologic advances such as extracorporeal membrane oxygenation and the increased utilization of high flow nasal cannula, the use of PGD as an outcome measure in clinical trials of ex vivo lung perfusion, enhancement of predictive algorithms incorporating biochemical risk factors, and the need for development of therapies targeted at improving PGD outcomes.

Human neutrophils can mimic myeloid-derived suppressor cells (PMN-MDSC) and suppress microbead or lectin-induced T cell proliferation through artefactual mechanisms

We report that human conventional CD15⁺ neutrophils can be isolated in the peripheral blood mononuclear cell (PBMC) layer during Ficoll gradient separation, and that they can impair T cell proliferation in vitro without concomitant neutrophil activation and killing. This effect was observed in a total of 92 patients with organ transplants, lung cancer or anxiety/depression, and in 18 healthy donors. Although such features are typically associated in the literature with the presence of certain myeloid-derived suppressor cell (PMN-MDSC) populations, we found that commercial centrifuge tubes that contained membranes or gels for PBMC isolation led to up to 70% PBMC contamination by CD15⁺ neutrophils, with subsequent suppressive effects in certain cellular assays. In particular, the suppressive activity of human MDSC should not be evaluated using lectin or microbead stimulation, whereas assays involving soluble or plate-bound antibodies or MLR are unaffected. We conclude that CD15⁺ neutrophil contamination, and associated effects on suppressor assays, can lead to significant artefacts in studies of human PMN-MDSC.

ISHLT Consensus Statement on adult and pediatric airway complications after lung transplantation: Definitions, grading system, and therapeutics

Airway complications remain a major cause of morbidity and mortality after cardiothoracic transplantation. The reported incidence of airway ischemic complications varies widely, contributed to by the lack of a universally accepted grading system and standardized definitions. Furthermore, the majority of the existing classification systems fail to integrate the wide range of possible bronchial complications that may develop after lung transplant. Hence, a Working Group was created by the International Society for Heart and Lung Transplantation with the aim of elaborating a universal definition of adult and pediatric airway complications and grading system. One such area of focus is to understand the problem in the context of a more standardized consensus of classifying airway ischemia. This consensus definition will have major clinical, therapeutics, and research implications.

Incidence, risk factors, and clinical implications of post-operative delirium in lung transplant recipients

BACKGROUND

Delirium significantly affects post-operative outcomes, but the incidence, risk factors, and long-term impact of delirium in lung transplant recipients have not been well studied.

METHODS

We analyzed 155 lung transplant recipients enrolled in the Lung Transplant Outcomes Group (LTOG) cohort at a single center. We determined delirium incidence by structured chart review, identified risk factors for delirium, determined whether plasma concentrations of 2 cerebral injury markers (neuron-specific enolase [NSE] and glial fibrillary acidic protein [GFAP]) were associated with delirium, and determined the association of post-operative delirium with 1-year survival.

RESULTS

Fifty-seven (36.8%) patients developed post-operative delirium. Independent risk factors for delirium included pre-transplant benzodiazepine prescription (relative risk [RR] 1.82; 95% confidence interval [CI] 1.08 to 3.07; p = 0.025), total ischemic time (RR 1.10 per 30-minute increase; 95% CI 1.01 to 1.21; p = 0.027), duration of time with intra-operative mean arterial pressure <60 mm Hg (RR 1.07 per 15-minute increase; 95% CI 1.00 to 1.14; p = 0.041), and Grade 3 primary graft dysfunction (RR 2.13; 95% CI 1.27 to 3.58; p = 0.004). Ninety-one (58.7%) patients had plasma available at 24 hours. Plasma GFAP was inconsistently detected, whereas NSE was universally detectable, with higher NSE concentrations associated with delirium (risk difference 15.1% comparing 75th and 25th percentiles; 95% CI 2.5 to 27.7; p = 0.026). One-year mortality appeared higher among delirious patients, 12.3% compared with 7.1%, but the difference was not significant (p = 0.28).

CONCLUSIONS

Post-operative delirium is common in lung transplant recipients, and several potentially modifiable risk factors deserve further study to determine their associated mechanisms and predictive values.

Cell-free hemoglobin promotes primary graft dysfunction through oxidative lung endothelial injury

Primary graft dysfunction (PGD) is acute lung injury within 72 hours of lung transplantation. We hypothesized that cell-free hemoglobin (CFH) contributes to PGD by increasing lung microvascular permeability and tested this in patients, ex vivo human lungs, and cultured human lung microvascular endothelial cells. In a nested case control study of 40 patients with severe PGD at 72 hours and 80 matched controls without PGD, elevated preoperative CFH was independently associated with increased PGD risk (odds ratio [OR] 2.75, 95%CI, 1.23-6.16, P = 0.014). The effect of CFH on PGD was magnified by reperfusion fraction of inspired oxygen (FiO2) ≥ 0.40 (OR 3.41, P = 0.031). Isolated perfused human lungs exposed to intravascular CFH (100 mg/dl) developed increased vascular permeability as measured by lung weight (CFH 14.4% vs. control 0.65%, P = 0.047) and extravasation of Evans blue-labeled albumin dye (EBD) into the airspace (P = 0.027). CFH (1 mg/dl) also increased paracellular permeability of human pulmonary microvascular endothelial cell monolayers (hPMVECs). Hyperoxia (FiO2 = 0.95) increased human lung and hPMVEC permeability compared with normoxia (FiO2 = 0.21). Treatment with acetaminophen (15 μg/ml), a specific hemoprotein reductant, prevented CFH-dependent permeability in human lungs (P = 0.046) and hPMVECs (P = 0.037). In summary, CFH may mediate PGD through oxidative effects on microvascular permeability, which are augmented by hyperoxia and abrogated by acetaminophen.