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To reduce adhesions after left ventricular assist device (LVAD) implantation, pericardial closure using an expanded polytetrafluoroethylene (ePTFE) patch has been suggested. However, as foreign material, ePTFE patches could increase the risk of infectious complications. In this single-center retrospective study, we investigated outcomes of pericardial closure using an ePTFE patch in LVAD implantation. We included all patients who underwent LVAD implantation at our center between 2011 and 2020 (n = 166). Primary endpoint was development of mediastinitis at any point of time between LVAD implantation and heart transplantation (HTx) or death. Secondary endpoint was overall survival. Preoperative and postoperative clinical data were collected to ensure comparability between the groups. We included 166 patients with LVAD. A total of 116 patients (70%) underwent pericardial closure using an ePTFE patch. There were significant differences between the groups in treatment setting, previous cardiac surgery, Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) level, development of driveline infection, and HTx. Patients with an ePTFE patch developed mediastinitis more frequently (16%) than patients without ePTFE patch (4%) ( p = 0.039). A significant difference in overall survival between the groups could not be confirmed ( p = 0.29). The use of PTFE patches for pericardial closure in LVAD implantation was associated with a higher incidence of mediastinitis, but not with a difference in overall survival., Competing Interests: Disclosure: The authors have no conflicts of interest to report., (Copyright © ASAIO 2023.)

Background: Cardiovascular morbidity is common in adults after lung transplantation (LTx) but has not been described for pediatric LTx recipients. Early subclinical cardiovascular damage is reflected by increases in pulse wave velocity (PWV; indicating arteriosclerosis), intima-media thickness (IMT; indicating atherosclerosis), and left ventricular mass index (LVMI; indicating left ventricular hypertrophy)., Methods: We annually assessed 47 pediatric LTx recipients in a prospective longitudinal study (144 observations, mean 3.1 visits/patient, range of 1-4 visits, mean follow-up 2.2 y)., Results: At inclusion, increased PWV and IMT were detected in 13% and 30%, respectively, and elevated LVMI was detected in 33%. Higher PWV was associated with male sex, longer time since LTx, higher diastolic blood pressure, and lower glomerular filtration rate. Male sex and lower hemoglobin levels were associated with higher IMT, and the presence of diabetes was associated with higher LVMI., Conclusions: Pediatric LTx recipients suffer from a high and sustained burden of subclinical cardiovascular damage. In light of improving long-term outcomes, cardiovascular morbidity needs to be addressed. Our analysis identified classical and nonclassical risk factors to be associated with the measures for cardiovascular damage, which could serve as targets for intervention., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

To assess whether MR diffusion imaging may be applied for non-invasive detection of renal changes correlating with clinical diagnosis of acute kidney injury (AKI) in patients after lung transplantation (lutx).Fifty-four patients (mean age 49.6, range 26-64 years) after lutx were enrolled in a prospective clinical study and underwent functional MR imaging of the kidneys in the early postoperative period. Baseline s-creatinine ranged from 39 to 112 μmol/L. For comparison, 14 healthy volunteers (mean age 42.1, range 24-59 years) underwent magnetic resonance imaging (MRI) using the same protocol. Renal tissue injury was evaluated using quantification of diffusion and diffusion anisotropy with diffusion-weighted (DWI) and diffusion-tensor imaging (DTI). Renal function was monitored and AKI was defined according to Acute-Kidney-Injury-Network criteria. Statistical analysis comprised one-way ANOVA and Pearson correlation.67% of lutx patients (36/54) developed AKI, 47% (17/36) had AKI stage 1, 42% (15/36) AKI stage 2, and 8% (3/36) severe AKI stage 3. Renal apparent diffusion coefficients (ADCs) were reduced in patients with AKI, but preserved in transplant patients without AKI and healthy volunteers (2.07 ± 0.02 vs 2.18 ± 0.05 vs 2.21 ± 0.03 × 10 mm/s, P < .05). Diffusion anisotropy was reduced in all lutx recipients compared with healthy volunteers (AKI: 0.27 ± 0.01 vs no AKI: 0.28 ± 0.01 vs healthy: 0.33 ± 0.02; P < .01). Reduction of renal ADC correlated significantly with acute loss of renal function after lutx (decrease of renal function in the postoperative period and glomerular filtration rate on the day of MRI).MR diffusion imaging enables non-invasive assessment of renal changes correlating with AKI early after lutx. Reduction of diffusion anisotropy was present in all patients after lutx, whereas marked reduction of renal ADC was observed only in the group of lutx recipients with AKI and correlated with renal function impairment.

Background: Lung retransplantation is a demanding procedure with outcomes lagging primary transplantation. We implemented less invasive surgical techniques aiming at improving early outcomes. Here, we wish to describe these techniques and analyze the clinical outcomes., Methods: Since April 2010, a protocol of less invasive techniques was applied to all lung retransplantations. This protocol comprises bilateral lung retransplantation via sternum-sparing anterolateral thoracotomies, off-pump surgery, and empiric administration of 2 g fibrinogen and 2 platelet concentrates. Patient charts were retrospectively reviewed starting in April 2010 until May 2016 for this study and compared with a cohort of patients undergoing lung retransplantation between January 2005 and March 2010., Results: From April 2010 through March 2016, 774 total lung transplantations were performed at our center, 49 were retransplantations. In the era January 2005 to March 2010, a total of 480 lung transplantations were performed, 38 of those being retransplantations. Mean operation time in the era April 2010 to May 2016 was significantly longer as compared with the era January 2005 to March 2010, median time until extubation was significantly shorter in the era April 2010 to May 2016 (1 [1-2] days vs 11.5 [1-24] days; P = 0.0009). Similarly, median intensive care unit stay time was shorter in the era April 2010 to May 2016 (4 [2-5.5] days vs 12.5 [3-30.5] days; P = 0.003). Patient survival was significantly better in the era starting in April 2010 at 30 days (98% vs 76.3%, P = 0.002) as well as at 1 year (80.6% vs 63.2%; P = 0.01)., Conclusions: Less invasive retransplantation of the lung via sternum-sparing anterolateral thoracotomies and off-pump is a safe procedure with low associated morbidity and favorable midterm survival.

Background: At our institution, until April 2013, patients who showed early donor specific anti-HLA antibodies (DSA) after lung transplantation were preemptively treated with therapeutic plasma exchange (tPE) and a single dose of Rituximab. In April 2013, we moved to a therapy based on IgM-enriched human immunoglobulins (IVIG), repeated every 4 weeks, and a single dose of Rituximab., Methods: This observational study was designed to evaluate the short-term patient and graft survival in patients who underwent IVIG-based DSA treatment (group A, n = 57) versus contemporary patients transplanted between April 2013 and January 2015 without DSA (group C, n = 180), as well as to evaluate DSA clearance in IVIG-treated patients versus historic patients who had undergone tPE-based treatment (group B, n = 56). Patient records were retrospectively reviewed. Follow-up ended on April 1, 2015., Results: At 6 months and 1 year of follow-up, group A had a survival similar to group C (P = 0.81) but better than group B (P = 0.008). Group A showed statistically nonsignificant trends toward improved freedom from pulsed-steroid therapy and biopsy-confirmed rejection over groups B and C. The DSA clearance was better in group A than group B at treatment end (92% vs 64%; P = 0.002) and last DSA control (90% vs 75%; P = 0.04)., Conclusions: Patients with new early DSA but without graft dysfunction that are treated with IVIG and Rituximab have similarly good early survival as contemporary lung transplant recipients without early DSA. The IVIG yielded increased DSA clearance compared with historic tPE-based treatment, yet spontaneous clearance of new DSA also remains common., Competing Interests: The authors declare no conflicts of interests.

Background: Chronic lung allograft dysfunction (CLAD) is the major outcome limitation for lung transplant recipients (LTR) after the first year, and therapies targeting immunological pathways show only limited success. Because microvesicles (MV) are biomarkers of endothelial dysfunction and coagulation but are also involved in immunological responses, we hypothesized that MV, found in bronchoalveolar lavage (BAL) fluids (BALF) of LTR at CLAD diagnosis, are elevated and potential prognostic biomarkers., Methods: The BALF was collected from 37 LTR at time point of CLAD diagnosis and 37 LTR without any complication at routinely performed BAL. The MV concentration and origin were determined by flow cytometry by detection of different antigens. Patient- and transplant-related risk factors were included in a retrospective statistical analysis., Results: The BALF-MV levels of epithelial and red blood cell (RBC) origin were significantly higher in CLAD patients (mean: 1533/μL and 158/μL) compared to controls (436/μL, 57/μL). The LTR with high levels of epithelial MV >580/μL showed a significantly shorter overall survival at 4 years after BAL (39.5%) compared to patients with low MV (66.4%) and this proofed to be an independent prognostic factor in multivariate Cox analysis (hazards ratio = 3.05). Furthermore, LTR with high levels of RBC MV ≥225/μL were also associated with worse disease-specific survival, with probabilities at 4 years after BAL of 85.8% vs. 36.0%., Conclusions: Epithelial and RBC BALF-MV are elevated at CLAD diagnosis, have a potential as biomarkers, and support the hypothesis of a pathway, including activation of coagulation and complement, endothelial barrier dysfunction, and microangiopathy.

Background: Despite improvement of lung preservation by the introduction of low-potassium dextran (LPD) solution, ischemia-reperfusion injury remains a major contributor to early post-lung transplant graft dysfunction and mortality. After favorable experimental data, Celsior solution was used in our clinical lung transplant program. Data were compared with our historic LPD cohort., Methods: Between January 2002 and January 2005, 209 consecutive lung transplantations were performed with LPD. These were compared to 208 transplants between February 2005 and September 2007 with Celsior. Endpoints included posttransplant PaO2/FiO2 ratio at different timepoints after intensive care unit (ICU) admission, posttransplant ventilation time, ICU stay and 30-day mortality, follow-up survival, and bronchiolitis obliterans syndrome-free survival., Results: Ratios of sex, urgency status, type of procedure, length of posttransplant ICU stay, and age did not show significant differences between the 2 groups. Mean ischemia times were significantly longer in the Celsior group (LPD, 355 ± 105 minutes vs Celsior, 436 ± 139 minutes, P < 0.001). Overall 3-year-survival (LPD, 66.5% vs Celsior, 72.0%; P = 0.25) was nonsignificantly improved in the Celsior cohort., Conclusions: A trend toward better survival (P = 0.09) and increased freedom from bronchiolitis obliterans syndrome (P = 0.03) was observed in the Celsior group despite prolonged ischemic times compared with LPD. Lung preservation with Celsior is safe and effective and may carry advantages.

Background: Bronchiolitis obliterans syndrome is caused by a fibroproliferative process in lung allografts resulting in irreversible damage. In this study, we induced obliterative bronchiolitis and studied the contribution of regulatory T cells to its development in immune-deficient mice receiving heterotopic porcine bronchus transplants, and major histocompatibility complex-mismatched porcine peripheral blood mononuclear cell. Furthermore, we aimed to corroborate our findings in a humanized mouse model., Methods: Heterotopic bronchus transplantation was performed in 33 NOD.rag(−/−)γc(−/−) mice, using miniature pigs as tissue donors.The recipient mice then either received saline (negative control), unsorted MHC-mismatched PBMC (positive control), PBMC enriched with CD4(+)CD25(high) cells or PBMC depleted of CD4(+)CD25(high) cells for reconstitution. The results were validated in 28 NOD.rag(−/−)γc(−/−) mice undergoing heterotopic human bronchus transplantation and reconstitution with allogeneic human PBMC., Results: Histological lesions similar to those typical for obliterative bronchiolitis developed in vivo after reconstitution with allogeneic PBMC and were more severe in animals engrafted with PBMC depleted of CD4(+)CD25(high) cells. In contrast, the group reconstituted with PBMC enriched with CD4(+)CD25(high) cells showed well-preserved histology. The results of the humanized model confirmed those obtained in the porcinized model., Conclusions: In conclusion, both porcinized and humanized mouse models of heterotopic subcutaneous bronchus transplantation imitate the in vivo development of bronchiolitis obliterans syndrome-like lesions and reveal its sensitivity to T-cell regulation.

Background: Bilateral lung transplantation (BLTx) is an established treatment for end-stage pulmonary hypertension (PH). Ventilator weaning failure and death are more common as in BLTx for other indications. We hypothesized that left ventricular (LV) dysfunction is the main cause of early postoperative morbidity or mortality and investigated a weaning strategy using awake venoarterial extracorporeal membrane oxygenation (ECMO)., Methods: In 23 BLTx for severe PH, ECMO used during BLTx was continued for a minimum of 5 days (BLTx-ECMO group). Echocardiography, left atrial (LA) and Swan-Ganz catheters were used for monitoring. Early extubation after transplantation was attempted under continued ECMO., Results: Preoperatively, all patients had severely reduced cardiac index (mean, 2.1 L/min/m2). On postoperative day 2, reduction of ECMO flow resulted in increasing LA and decreasing systemic blood pressures. On the day of ECMO explantation (median, postoperative day 8), LV diameter had increased; LA and blood pressures remained stable. Survival rates at 3 and 12 months were 100% and 96%, respectively. Data were compared to two historic control groups of BLTx without ECMO (BLTx ventilation) or combined heart-lung transplantation for severe PH., Conclusion: Early after BLTx for severe PH, the LV may be unable to handle normalized LV preload. This can be effectively bridged with awake venoarterial ECMO.

Background: Primary graft dysfunction (PGD) is the most important cause of early morbidity and mortality in lung transplantation (LTX) with an incidence of 8% to 20%. We hypothesized that application of C1-esterase-inhibitor (C1-INH) in LTX-recipients showing early signs of severe PGD would attenuate the condition., Methods: Starting as of May 2010, all recipients showing a PaO2/FiO2 ratio of less than 100 as early sign of PGD at first measurement in the OR were immediately treated with C1-INH. Postoperative courses of C1-INH-treated recipients were compared with a subgroup of recipients that developed severe PGD (PGD3-group) within 72 hours after LTX but did not receive C1-INH. Additionally, a third group consisting of all remaining recipients was assembled., Results: A total of 275 LTX were performed between May 2010 and September 2012 at our center. Among these, 24 patients (8.7%) revealed a first PaO2/FiO2 ratio less than 100 and were treated with C1-INH (C1-INH-group). The PGD3-group consisted of 14 patients; the control cohort consisted of 237 patients. PGD scores were significantly higher in the C1-INH-group and PGD3-group as compared with the control group at all times postoperatively. ICU stay was longest in the PGD3 cohort and prolonged in C1-INH patients compared with the control group (29 [2-70] vs. 9 [2-83] vs. 3 [1-166] days, P=0.002). One-year survival in the PGD3-cohort was 71.4%, the C1-INH-treated-group had a one-year-survival of 82.5%, the control group had the best outcome (95%) (P=0.001)., Conclusion: Treatment of PGD with C1-INH led to acceptable outcome. Although survival in the C1-INH treated patients was lower than in the remaining collective, it was as good or better, compared with the PGD3 group and as what is internationally regarded as reasonable after LTX.

Background: Short-term posttransplantation survival and health-related quality of life (HRQoL) is exceptionally high for all patients after organ transplantation; however, predictors of the HRQoL outcome are not well understood. Trajectories of patients' perceived benefit/burden ratio associated with the transplant procedure may differ when taking the organ type for transplantation into account., Methods: A prospective, single-center cohort study assessed the trajectories of 354 patients after kidney (n=165), liver (n=53), heart (n=24), and lung (n=112) transplantation at 2, 6, 12, and 24 months with respect to psychosocial outcomes (HRQoL, anxiety, depression, social support, and work performance)., Results: Mean age was 50±13 years, and 61.6% were male in the overall sample. Demographics differed with respect to organ type. HRQoL measured by the mean SF-36 Physical Component Scale was 36.8 (95% confidence interval, 35.7-37.8) and 48.9 (95% confidence interval, 47.2-49.7) for the Psychosocial Component Scale for the entire sample at 2 months and showed a marginal decrease until 24 months after transplantation. Overall, HRQoL increased for all organ types with differing trajectories. Liver patients reported the lowest HRQoL benefit for the majority of the physical (P≤0.01) and psychosocial (P≤0.01) SF-36 subscales. Anxiety (17.4%) and depression (13.8%) were prevalent in the overall sample. Depression symptoms impaired HRQoL outcomes in both SF-36 components and unemployment impacted the SF-36 psychosocial outcomes., Conclusions: HRQoL improved after transplantation for all four types of transplant, but the trajectories were different. Regular screening for depression symptoms may diminish psychologic disorders and distress after transplantation and thus may further improve outcomes.

Background: Advanced chronic lung allograft dysfunction limits survival after lung transplantation. We hypothesize that patients with chronic lung allograft dysfunction can be subdivided by exercise tolerance in two groups, and quality of life (QOL) and survival differ between the groups., Methods: A single-center, cross-sectional, partly prospective, study was performed in our outpatient clinic between July and November 2011, including all patients with a forced expiratory volume in 1 s <50% baseline. Respiratory parameters, 6-min walk test, and QOL were measured. Patients with low exercise capacity were defined as 6-min walk test <50% predicted or use of rollator or wheelchair., Results: Fifty-two patients consented to participating in the study and 22 demonstrated low exercise capacity. These patients had pathologic respiratory muscle function (P=0.005) and decreased inspiratory capacity (IC; P=0.001). QOL was significantly reduced. Multivariate analysis proved that low IC (hazard ratio, 17.9; 95% confidence interval, 2.8-111; P=0.002) and increased P0.1/Pimax (hazard ratio, 7.1; 95% confidence interval, 1.4-35.8; P=0.016) were independently associated with decrease exercise capacity., Conclusion: Heterogeneity of patients with advanced lung allograft dysfunction regarding exercise tolerance might result from altered IC and impaired respiratory muscle function.

Purpose of Review: Re-transplantation of the lung has come of age. Here, we wish to review the recent literature on the topic and discuss clinical implications., Recent Findings: Many large volume transplant centres routinely perform lung re-transplantation with satisfactory outcomes. The main indication is bronchiolitis obliterans syndrome, that is chronic rejection of a previous lung transplant. Other indications, such as primary graft failure or early airway complications, are regarded with more caution, as outcomes compare less favourably with those following primary transplantation., Summary: Re-transplantation of the lung can be performed safely and with outcomes rivalling those of primary transplants in carefully selected recipients with chronic rejection of a previous transplant.

Background: An obstructive pattern in pulmonary function test is common after lung transplantation (LTx) and may be caused by multiple disorders. In this study, the impact and outcome of an obstructive spirometric pattern identified in transplant recipients early posttransplantation were investigated., Methods: Analyzing all patients undergoing double LTx between September 1, 2007, and October 1, 2009, we separated patients with an obstructive (forced expiratory volume in 1 sec [FEV(1)]: vital capacity [VC] <0.7) and a nonobstructive pattern (FEV(1):VC ≥0.7) in pulmonary function tests 3 months after transplantation. Pulmonary function measurement, bronchoscopy, laboratory parameter, computed tomography morphology, mortality, and bronchiolitis obliterans syndrome (BOS)-free survival were analyzed up to 36 months after transplantation. In addition, information about donor lungs were collected (age, smoking history, and blood gas before lung harvesting)., Results: From 122 recipients included, 17 (14%) exhibited an obstructive pattern. Recipients with an early obstructive pattern were older at transplantation, had significantly decreased FEV(1), increased total lung capacity, and donor organ with lower pO(2) when ventilated with 100% oxygen before retrieval. Obstructive patients developed their best FEV(1) earlier after LTx and demonstrated a significant increase in BOS development (47% vs. 14%)., Conclusions: An obstructive lung function pattern early after LTx was associated with earlier development of BOS and may have negative impact on outcome after double LTx. Early obstructive pattern after transplantation might be an indication of structural donor lung injury.

Background: To determine whether the hydroxy-3-methylglutaryl coenzyme A reductase inhibitor pravastatin has a graft-protective effect, we retrospectively analyzed 502 patients who had undergone lung transplantation in Hannover., Methods: Propensity scores have been calculated for each patient and compared between two groups. Cox Hazard analyses were performed for different parameters (e.g., basic parameters of patients, underlying diagnoses, different operations, and important organ functions after lung transplantation). Lung function after transplantation was monitored using repeated measurement analyses. Additionally, conditional Kaplan-Meier survival analyses were used to explore the impact of different diagnoses, the severity of bronchiolitis obliterans, the type of transplantation, and different immunosuppressant regimes on patient survival., Results: The results indicate a strong association between the postoperative administration of statins and the improvement of survival, maintenance of graft (lung) function, and slowing of the onset of bronchiolitis obliterans., Conclusion: These findings suggest a new postoperative therapeutic focus for maintaining graft function.

Background: Obstructive airway complications (OACs) are a significant cause of morbidity after lung transplantation (LTx). Endoscopic evaluation early after LTx may help earlier identification of patients at risk., Methods: Anastomotic healing process was prospectively evaluated in 169 LTx recipients by bronchoscopy between 2007 and 2009 in a single center. Bronchoscopies were performed on day 7, 14, 21, 90, 180, and 360 after LTx. A scoring system of airway healing was constructed., Results: In 42 of 169 patients (25%), OAC occurred. Dehiscence (P≤0.001), extensive necrosis (P=0.001), fibrinous plug (P≤0.001), and mucosal healing at segmental level (P=0.001) on day 21 after LTx were significantly associated with later occurrence of OAC. The hereby developed Mucosal Airway Score for Healing (0-8 points, cutoff >3 points) proved to predict later OAC in 67 patients of validation phase (sensitivity=0.97; specificity=0.93; positive predictive value=0.85; and negative predictive value=0.96). Substantial interobserver agreement using Mucosal Airway Score for Healing was achieved (κ=0.617). All airway complications were managed with endoscopic intervention, and no surgical treatment was necessary., Conclusion: Endoscopic appearance on day 21 after LTx predicts later occurrence of OAC. The resulting scoring system may be used in the early postoperative period as a tool to assess preventive strategies.

Background: This study was designed to analyze the role of postoperative donor cell chimerism for the induction and maintenance of transplantation tolerance in a porcine lung transplantation model., Methods: Left-sided single lung transplantation from major histocompatibility mismatched male donors was performed in 27 female minipigs. All received a 28-day course of pharmacologic immunosuppression using various agents, some in combination with preoperative irradiation. Groups for eventual analysis were strictly defined by outcome, that is, pigs with acute rejection before postoperative day 178 (n=16) were allocated into one group, long-term surviving animals (n=11) into the other. Peripheral blood chimerism was monitored by flow cytometry and real-time polymerase chain reaction. Intragraft chimerism was detected from bronchoalveolar lavage fluid (BALF) by fluorescent in situ hybridization., Results: Blood chimerism peaked 1 hour after transplantation and was significantly higher in the group of long-term survivors at that time. Thereafter chimerism rapidly decreased, but tended to remain higher in long-term survivors. In case of acute rejection donor cells were lost, but remained detectable for up to 36 postoperative months in tolerant animals. In BALF, the percentage of male nuclei was equally high under immunosuppression in both groups. Rejecting animals showed a rapid decrease of Y-bearing cells in BALF after drug withdrawal and an almost complete loss when acute rejection occurred. In tolerant pigs, intragraft chimerism remained detectable throughout the follow-up., Conclusions: This study demonstrates a clear correlation of donor leukocyte chimerism with long-term allograft survival in a porcine allogeneic lung transplantation model.

Background: The trans vivo delayed-type hypersensitivity (DTH) assay has been used for monitoring the immune status of clinical transplant recipients. Here we tested the hypothesis that the assay can reveal control of allograft rejection by CD25CD4 regulatory T cells (Treg)., Methods: CBA.Ca (H2) recipients of heterotopic C57BL/10 (H2, B10) heart transplants were untreated or pretreated with anti-CD4 antibody and donor-specific blood. This protocol has been shown previously to induce operational tolerance to alloantigens that is dependent on CD25CD4 Treg. Four weeks after transplantation leukocytes were harvested and used for the trans vivo DTH assay. Cells were stimulated with irradiated B10 leukocytes or subcellular antigen and injected into ear pinnae of immune deficient CB17.SCID.beige hosts., Results: Stimulation of leukocytes from recipients rejecting B10 cardiac allografts with recall alloantigen caused a "strong" swelling response, whereas similar stimulation of leukocytes from operationally tolerant mice resulted in significantly less swelling (n=17; P=0.003). When CD25 T cells were depleted from "tolerant" leukocytes, the swelling response triggered was similar to that obtained using cells from rejecting animals (P<0.001), while coinjection of purified CD25CD4 cells from tolerant recipients with rejecting cells suppressed the swelling response (P=0.007) to the level observed with cells from tolerant mice. Both the effector and the regulatory response were triggered by indirect allorecognition and blocking experiments showed that the regulation observed was dependent on cytoxic T lymphocyte antigen (CTLA) 4., Conclusion: The trans vivo DTH assay can be used to reveal regulation mediated by CD25CD4 T cells and is CTLA4 dependent.

Background: CD25+CD4+ regulatory T cells have been shown to suppress alloimmunity in various experimental settings. Here, we hypothesized that alloantigen-reactive regulatory T cells would reduce the severity of transplant arteriosclerosis., Methods: CD25+CD4+ T cells from CBA mice that were pretreated with C57BL/6 (B.6) blood (donor-specific transfusion, DST) and nondepleting anti-CD4 Ab (YTS 177) were cotransferred with naïve CBA CD25-CD4+"effector" T cells into CBA-rag-/- mice. These animals received aorta transplants from B.6 CD31-/- donors. CBA wild-type recipients of B.6 aorta grafts were pretreated with 177/DST directly. Some animals received 6x10(5) CD25+CD4+ T cells from pretreated mice to augment regulation on day -1. Grafts were harvested on day 30., Results: Luminal occlusion of the graft caused by neointima formation was 29.3+/-19.4% (n=5) after transfer of effector T cells only. Co-transfer of CD25+CD4+ regulators reduced occlusion significantly (2.4+/-3.3%, n=3; P=0.009). This effect was partially abrogated in the presence of a CTLA4 blocking Ab (11.1+/-4.7%, n=4; P=0.008). Pretreating immunocompetent CBA recipients of B.6 aortic allografts with 177/DST did not reduce transplant arteriosclerosis significantly (43.0+/-15.7%, n=5 vs. 56.6+/-16.8%, n=5; 177/DST vs. controls; P=0.22). However, when pretreated primary CBA recipients received an additional transfer of 6 x 10(5) CD25+CD4+ T cells procured from other mice pretreated with 177/DST before transplantation, luminal occlusion of the graft was markedly reduced (33.0+/-7.6%, n=5; P=0.002)., Conclusion: Regulatory T cells generated in vivo to alloantigen can prevent CD25-CD4+ T-cell-mediated transplant arteriosclerosis. In immunocompetent recipients, these cells have potential to be used as cellular immunotherapy to control transplant arteriosclerosis.

Background: A simplified conditioning protocol including single-dose preoperative thymic and low-dose whole body irradiation with or without subsequent donor bone marrow transplantation (BMTx) can be applied in porcine lung transplantation. We hypothesized that this protocol would prolong allograft survival., Methods: Left-sided single lung transplantation from major histocompatibility complex (MHC)-mismatched donors was performed in 27 minipigs. Recipients received whole body (1.5 Gy) and thymic irradiation (7 Gy) before transplantation (IRR group, n=6), intravenous immunosuppression with methylprednisolone, cyclosporine, and azathioprine for 27 postoperative days (IS group, n=5) or both (IRR+IS group, n=10). BMTx group recipients were treated with irradiation, immunosuppression and a donor bone marrow infusion on postoperative day 1. Peripheral blood leukocyte phenotype and donor cell chimerism were monitored by flow cytometry. Purified CD25+ T cells from long-term survivors or rejecting animals were used for in vitro MLR suppression assays., Results: Median graft survival was: IRR 12 days, IS 55 days, IRR+IS 239 days, and BMTx 80 days (P<0.0001). Early peripheral blood macrochimerism was substantial in both the IRR+IS and the BMTX group but was lost in all groups after day 80. The frequency and suppressive function of CD4+CD25+ T cells were enhanced in IRR+IS group long-term survivors., Conclusion: Although donor bone marrow infusion was not beneficial in our model, a substantial proportion of the animals treated with irradiation and a 28-day course of immunosuppression accepted their lung allografts long term. The mechanism involved in maintaining allograft tolerance may be based on peripheral T-cell regulation.