Implications of drug intoxication on donor utilization and outcomes in liver transplantation.

INTRODUCTION: This study evaluates the implications of drug intoxication (DI) on donor utilization and outcomes in liver transplantation (LT). METHODS: The UNOS STAR database was evaluated for all potential donors and adult, first-time, whole LT between 2005 and 2019. Logistic regression analyses evaluated liver utilization; proportional hazards modeling assessed risk of 1-year graft loss. RESULTS: A total of 132 783 potential donors (10 205, 7.7% from DI), and 90 612 adult LT were identified (7490, 8.3% from DI). DI donors had median age 32 years (IQR 26-40 years, p < .001), were 42.6% female (n = 4346), and 15.5% were DCD donors (n = 1583). Utilization of DI donors changed over time, such that by 2015-2019 they were the most likely donor cause of death (COD) to be utilized. Among LT recipients, there were insignificant differences (<2% variance) in age, gender, ethnicity, and etiology of liver disease according to donor COD. Recipients with MELD scores >30 more frequently received grafts from donors with trauma (23.8%) and DI (21.8%) versus cardiovascular (20.0%) and CVA/stroke (19.9%, p < .001). Among DBD donors, DI-COD was associated with superior 1-year graft survival compared to donors from trauma (HR 1.172, 95% CI 1.057-1.300) and CVA/stroke (HR 1.404, 95% CI 1.264-1.561, p < .001). Donor COD was not significantly associated with 1-year graft loss among DCD donors. CONCLUSIONS: There is an increased likelihood of donor utilization when COD is drug overdose and an increased likelihood of 1-year graft survival compared to donors from trauma, CVA/stroke, and other COD.

A Multi-Modal Approach to Islet and Pancreas Transplantation With Calcineurin-Sparing Immunosuppression Maintains Long-Term Insulin Independence in Patients With Type I Diabetes.

Long-term success in beta-cell replacement remains limited by the toxic effects of calcineurin inhibitors (CNI) on beta-cells and renal function. We report a multi-modal approach including islet and pancreas-after-islet (PAI) transplant utilizing calcineurin-sparing immunosuppression. Ten consecutive non-uremic patients with Type 1 diabetes underwent islet transplant with immunosuppression based on belatacept (BELA; n = 5) or efalizumab (EFA; n = 5). Following islet failure, patients were considered for repeat islet infusion and/or PAI transplant. 70% of patients (four EFA, three BELA) maintained insulin independence at 10 years post-islet transplant, including four patients receiving a single islet infusion and three patients undergoing PAI transplant. 60% remain insulin independent at mean follow-up of 13.3 ± 1.1 years, including one patient 9 years after discontinuing all immunosuppression for adverse events, suggesting operational tolerance. All patients who underwent repeat islet transplant experienced graft failure. Overall, patients demonstrated preserved renal function, with a mild decrease in GFR from 76.5 ± 23.1 mL/min to 50.2 ± 27.1 mL/min (p = 0.192). Patients undergoing PAI showed the greatest degree of renal impairment following initiation of CNI (56% ± 18.7% decrease in GFR). In our series, repeat islet transplant is ineffective at maintaining long-term insulin independence. PAI results in durable insulin independence but is associated with impaired renal function secondary to CNI dependence.

Simultaneous thoracic and abdominal donation after circulatory death organ recovery: the abdominal surgeon's perspective.

PURPOSE OF THE REVIEW: To summarize the international experience with heart-liver (joint) donation after circulatory death (DCD) procurements and to explore the technical challenges in joint abdominal and thoracic DCD procurement. RECENT FINDINGS: Following completion of the Donors After Circulatory Death Heart Trial in the US, combined thoracic and abdominal DCD is poised to become the standard of care, expanding access to life-saving heart and lung allografts. DCD heart procurement relies on collection of donor blood for priming of the normothermic perfusion pump, which delays cooling of abdominal organs and increases risk of ischemic injury. We review the effect of donor ischemia time on abdominal organs, with several proposed technical solutions to optimize transplant outcomes for all organs. SUMMARY: The strategies reviewed in this manuscript may inform clinical decision-making, preoperative coordination between thoracic and abdominal procurement teams, and surgical technique for joint DCD procurements. Several approaches to organ procurement organization (OPO) and national policy, as well as future areas of focus for research are proposed.

Current outcomes in islet versus solid organ pancreas transplant for ß-cell replacement in type 1 diabetes.

PURPOSE OF REVIEW: With continued optimization of islet isolation and immunosuppression protocols, the medium-term rates of insulin independence following islet transplantation have improved significantly. This review evaluates the most up-to-date outcomes data for both solid organ pancreas and islet transplantation to develop an algorithm for selection of ß-cell replacement in type 1 diabetes patients. RECENT FINDINGS: Solid organ pancreas and islet transplantation have both displayed improved rates of 5-year insulin independence, largely attributable to improvements in immunosuppressive regimens. The medium-term rates of insulin independence following islet transplantation in highly selected type 1 nonuremic diabetic recipients is beginning to approach the success rates observed following solitary pancreas transplantation. SUMMARY: Although pancreas transplantation has historically been favored for ß-cell replacement, current outcomes following islet transplantation justify the use of this minimally invasive therapy in carefully selected patients. Pancreas transplant remains the procedure of choice for ß-cell replacement in uremic patients. Islet transplantation should be considered in nonuremic patients with low BMI and low insulin requirements, patients lacking the cardiovascular reserve to undergo open abdominal surgery, or patients who elect to forego the risks of a major operation in exchange for an increased risk of islet graft failure.

Organ Utilization Rates from Non-Ideal Donors for Solid Organ Transplant in the United States.

Background: Non-ideal donors provide acceptable allografts and may expand the donor pool. This study evaluates donor utilization across solid organs over 15-years in the United States. Methods: We analyzed the OPTN STAR database to identify potential donors across three donor eras: 2005-2009, 2010-2014, and 2015-2019. Donors were analyzed by a composite Donor Utilization Score (DUS), comprised of donor age and comorbidities. Outcomes of interest were overall and organ-specific donor utilization. Descriptive analyses and multivariable logistic regression modeling were performed. p-values < 0.01 considered significant. Results: Of 132,465 donors, 32,710 (24.7%) were identified as non-ideal donors (NID), based on a DUS ≥ 3. Compared to ideal donors (ID), NID were older (median 56 years, IQR 51-64 years vs. 35 years, 22-48 years, p < 0.001) and more frequently female (44.3% vs. 39.1%, p < 0.001), Black (22.1% vs. 14.6%, p < 0.001) and obese (60.7% vs. 19.6%, p < 0.001). The likelihood of overall DBD utilization from NID increased from Era 1 to Era 2 (OR 1.227, 95% CI 1.123-1.341, p < 0.001) and Era 3 (OR 1.504, 1.376-1.643, p < 0.001), while DCD donor utilization in NID was not statistically different across Eras. Compared to Era 1, the likelihood of DBD utilization from NID for kidney transplantation was lower in Era 2 (OR 0.882, 0.822-0.946) and Era 3 (OR 0.938, 0.876-1.004, p = 0.002). The likelihood of NID utilization increased in Era 3 compared to Era 1 for livers (OR 1.511, 1.411-1.618, p < 0.001), hearts (OR 1.623, 1.415-1.862, p < 0.001), and lungs (OR 2.251, 2.011-2.520, p < 0.001). Conclusions: Using a universal definition of NID across organs, NID donor utilization is increasing; however, use of DUS may improve resource utilization in identifying donors at highest likelihood for multi-organ donation.

Incidence and Outcomes of Simultaneous Thoracoabdominal Triple Organ Transplantation in the United States.

BACKGROUND: This study aims to evaluate patient outcomes of simultaneous triple organ transplants, which may provide insight into optimal donor allocation while maximizing recipient benefit. METHODS: Triple organ transplants and their corollary dual organ transplants were identified using the United Network for Organ Sharing database. Triple organ transplants evaluated included heart-lung-kidney (n = 12) and heart-liver-kidney (n = 37). Heart-lung-kidney recipients were compared with heart-lung (n = 325), lung-kidney (n = 91), and heart-kidney (n = 2022) groups. Heart-liver-kidney recipients were compared with heart-liver (n = 451), liver-kidney (n = 10422), and heart-kidney (n = 2517) recipients. Patient survival outcomes were calculated using the Kaplan-Meier method and compared using log-rank tests. RESULTS: Patients undergoing triple organ transplants showed similar 10-year survival as their corresponding dual organ transplant cohorts. Patient survival estimate at 10 years for the heart-lung-kidney group was 45%, with no statistically significant difference in survival when compared with dual organ groups (P = .16). Survival estimates at 10 years for the heart-liver-kidney group was 49%, with no statistically significant difference in survival when compared with dual organ groups (P = .06). CONCLUSION: Despite the surgical burden of adding a third organ transplant, heart-liver-kidney and heart-lung-kidney have similar survival outcomes to dual organ equivalents and represent a reasonable allocation option in well-selected patients.

Development and validation of a biomarker index for HCC treatment response.

BACKGROUND: Serum AFP-L3%, AFP, and DCP are useful biomarkers for HCC detection, but their utility in assessing treatment response remains unknown. We aim to evaluate the accuracy of a biomarker model in the detection of posttreatment viable tumors. METHODS: For model derivation, recipients with HCC undergoing liver transplant from 2018 to 2022 who had biomarkers collected within 3 months before transplant were included. We developed a generalized linear model for detecting posttreatment viable tumors with the 3 biomarkers as covariates, which we termed the "LAD Score." An independent cohort of 117 patients with HCC was used for external validation. RESULTS: Among 205 recipients of transplant, 70.2% had evidence of viable tumor on explant. The median LAD score was higher among patients with viable versus nonviable tumors (1.06 vs. 0.465, p < 0.001). The LAD score had a sensitivity of 55.6% and a specificity of 85.1% at the cutoff of 0.927, which was more accurate than imaging for detecting posttreatment viable tumors (AUROC 0.736 vs. 0.643, respectively; p = 0.045). The superior performance of the LAD score over imaging is primarily driven by its greater accuracy in detecting tumors <2 cm in diameter (AUROC of the LAD score 0.721 vs. imaging 0.595, p = 0.02). In the validation data set, the LAD score had an AUROC of 0.832 (95% CI: 0.753, 0.911) with a sensitivity of 72.5% and a specificity of 89.4% at the cutoff of 0.927. CONCLUSIONS: Our findings suggest the utility of LAD score in treatment response assessment after locoregional therapy for HCC, particularly in detecting small tumors. A larger prospective study is in progress to validate its accuracy and evaluate its performance in recurrence monitoring.

Drug Overdose and Cardiovascular Deaths Among Deceased Organ Donors: Implications for Donor Utilization and Data Reporting.

BACKGROUND The present study evaluated expanded cause of death (COD) definitions and its implications on donor utilization for solid organ transplantation. MATERIAL AND METHODS The OPTN Standard Transplant and Research file was queried for potential donors between 2005 and 2019. Donor- and organ-specific utilization were evaluated. Expanded donor COD were identified: trauma, cardiovascular (CV), cerebrovascular accident (CVA) or stroke, drug intoxication (DI), anoxia not otherwise specified (NOS), and other. Descriptive analyses and multivariable logistic regression analyses for donor utilization were performed. RESULTS Among 132 783 potential donors identified, the most common COD was CVA/Stroke (n=44 707, 33.7%), followed by trauma (n=43 356, 32.7%), CV (n=20 053, 15.1%), anoxia-NOS (n=12 261, 9.2%), DI (n=10 205, 7.7%), and other causes (n=2201, 1.7%). Significant differences between CV, DI, and anoxia-NOS groups existed for donor age, sex, ethnicity, body mass index, and comorbidities. Donors from trauma had the highest unadjusted utilization rate (97.2%) while CV donors had the lowest (90.1%). Multivariable analysis of brain-dead donors (DBD) showed that compared to trauma, donors from DI had higher likelihood of utilization (odds ratio 1.217, 95% 1.025-1.446) while CV donors were lower (OR 0.717, 95% CI 0.642-0.800, P<0.001). Among donation after circulatory death (DCD) donors, there was decreased utilization compared to trauma for both CV (OR 0.607, 95% CI 0.523-0.705) and DI (OR 0.754, 95% CI 0.603-0.914, P<0.001). CONCLUSIONS Current COD definitions should be expanded to capture significant differences in the donor population. DI donors are the fastest growing cohort and the most likely utilized DBD donors, while trauma donors remain the most likely utilized DCD donors.

A Retrospective Evaluation of Changing Health Characteristics Amongst Deceased Organ Donors in the United States.

BACKGROUND: The availability of suitable donor organs remains a limiting factor to performing life-saving transplant operations. This study evaluates changes in the health of the donor population and its influence on organ use in the United States. METHODS: A retrospective analysis was performed using the OPTN STAR data file from 2005 to 2019. Three donor eras were defined: 1) 2005 to 2009, 2) 2010 to 2014, and 3) 2015 to 2019. The primary outcome was donor use, defined as transplantation of at least one solid organ. Descriptive analyses were performed, and associations of donor use were examined with multivariable logistic regression models. P values <.01 were considered significant. RESULTS: The cohort included 132,783 potential donors of which 124,729 (93.9%) were used for transplantation. Donor median age was 42 years (interquartile range 26-54), 53,566 (40.3%) were female, and 88,209 (66.4%) were White, 21,834 (16.4%) were black, and 18,509 (13.9%) were Hispanic. Compared with donors from Eras 1 and 2, donors in Era 3 were younger (P < .001), had higher body mass index (BMI) (P < .001), increased rates of diabetes mellitus (DM) (P < .001), hepatitis C virus (HCV) positivity (P < .001) and more comorbidities (P < .001). Multivariable modeling found donor BMI, DM, hypertension, and HCV status as health factors significantly associated with donor use. Compared with Era 1, there was increased use in Era 3 of donors with BMI ≥30 kg/m2, DM, hypertension, HCV-positive status, and donors with ≥3 comorbidities. CONCLUSIONS: Despite an increasing prevalence of chronic health problems in the donor population, donors with multiple comorbid conditions are more likely to be used for transplantation in recent years.

Preserved 2-y Liver Transplant Outcomes Following Simultaneous Thoracoabdominal DCD Organ Procurement Despite Effects on Liver Utilization Rate.

Background: Current techniques for donation after circulatory determination of death (DCD) heart procurement, through either direct procurement and machine perfusion or thoracoabdominal normothermic regional perfusion (NRP), have demonstrated excellent heart transplant outcomes. However, the impact of thoracoabdominal DCD (TA-DCD) heart procurement on liver allograft outcomes and utilization is poorly understood. Methods: One hundred sixty simultaneous heart and liver DCD donors were identified using the United Network for Organ Sharing/Organ Procurement and Transplantation Network database between December 2019 and July 2021. Liver outcomes from TA-DCD donors were stratified by heart procurement technique and evaluated for organ utilization, graft survival, and patient survival. Results were compared with abdominal-only DCD (A-DCD; n = 1332) and donation after brain death (DBD; n = 12 891) liver transplants during the study interval. Kaplan-Meier methods with log-rank testing were used to evaluate patient and graft survival. Results: One hundred thirty-three of 160 livers procured from TA-DCD donors proceeded to transplant. TA-DCD donors were younger (mean 28.26 y; P < 0.0001) with lower body mass index (mean 26.61; P < 0.0001) than A-DCD and DBD donors. TA-DCD livers had equivalent patient survival ( P = 0.893) and superior graft survival (P = 0.009) compared with A-DCD. TA-DCD livers had higher rates of organ discard for long warm ischemia time (37.0%) than A-DCD (20.5%) and DBD (0.5%; P < 0.0001), with direct procurement and machine perfusion procurements leading to a higher discard rate (18.5%) than NRP procurements (7.4%). Conclusions: Liver transplants after TA-DCD donation demonstrated equivalent patient outcomes and excellent graft outcomes. NRP procurements resulted in the lowest rate of organ discard after DCD donation and may represent an optimal strategy to maximize organ utilization.

Donation after circulatory death heart procurement strategy impacts utilization and outcomes of concurrently procured abdominal organs.

INTRODUCTION: The impact of donation after circulatory death (DCD) heart procurement techniques on the utilization and outcomes of concurrently procured DCD livers and kidneys remains unclear. METHODS: Using the United Network for Organ Sharing database, we identified 246 DCD donors whose heart was procured using direct procurement and ex-situ machine perfusion and 128 DCD donors whose heart was procured using in-situ thoracoabdominal normothermic regional perfusion (12/2019-03/2022). We evaluated the transplantation rate of concurrently procured DCD livers and kidneys (defined as the number of organs transplanted/total number of organs available for procurement) and their post-transplant outcomes. RESULTS: The transplantation rate of concurrently procured DCD livers was higher with in-situ perfusion compared to direct procurement (67.1% vs 56.5%, p = 0.045). After excluding pediatric, multiorgan, and repeat transplant recipients, there was no difference in 6-month liver graft failure rate (direct procurement 0.9% vs in-situ perfusion 0%, p > 0.99). Recipients of kidneys procured with in-situ perfusion had less delayed graft function (11.3% vs 41.5%, p < 0.0001) shorter length of stay, and lower serum creatinine at discharge (both p < 0.05). Six-month recipient survival in the direct procurement and in-situ perfusion group were similar after DCD liver and kidney transplantation (p = 0.24 and 0.79 respectively). CONCLUSIONS: Compared to direct procurement, DCD heart procurement with in-situ thoracoabdominal normothermic regional perfusion was associated with increased utilization of DCD livers and a lower incidence of delayed graft function in concurrently procured DCD kidneys. Broader implementation of DCD heart transplantation must maximize the transplant potential of concurrently procured abdominal organs and ensure their successful outcomes.

Both donor specific and non-donor specific HLA antibodies reduced in recipients post simultaneous liver/kidney transplant.

It has been suggested that the liver allograft can protect the kidney allograft from antibody mediated rejection in simultaneous liver/kidney transplant (SLK) recipients by reducing preexisting donor specific antibodies (DSA) via adsorption of DSA by the liver allograft. Recently, the SLK allocation system was altered to provide a kidney safety net to those who do not recover native kidney function after liver transplant. However, the kidney transplant under the safety net creates a theoretical challenge for sensitized patients as the liver graft may not be able to adsorb human leukocyte antigen (HLA) antibodies against the kidney under the safety net because the liver and kidney grafts are from different donors and may carry different HLA antigens. This prompts us to examine levels of non-donor specific HLA antibodies in SLK recipients in our hospital. We found that levels of both DSA and non-DSA decreased post SLK transplant. The presence of preexisting DSA was also not associated with kidney graft survival and antibody mediated rejection in SLK recipients. Our results indicate that the liver transplant can reduce non-DSA, which may increase the pool of compatible kidneys offered under the safety net program for sensitized patients.

Procurement of Deceased Donor Parathyroid Glands With the Aid of Near-infrared Autofluorescence Imaging.

Parathyroid allotransplantation is a burgeoning treatment for severe hypoparathyroidism. Deceased donor parathyroid gland (PTG) procurement can be technically challenging due to lack of normal intraoperative landmarks and exposure constraints in the neck of organ donors. In this study, we assessed standard 4-gland exposure in situ and en bloc surgical techniques for PTG procurement and ex vivo near-infrared autofluorescence (NIRAF) imaging for identification of PTGs during organ recovery. Methods: Research tissue consent was obtained from organ donors or donor families for PTG procurement. All donors were normocalcemic, brain-dead, solid organ donors between 18 and 65 y of age. PTGs were procured initially using a standard 4-gland exposure technique in situ and subsequently using a novel en bloc resection technique after systemic organ preservation flushing. Parathyroid tissue was stored at 4 °C in the University of Wisconsin solution up to 48 h post-procurement. Fluoptics Fluobeam NIRAF camera and Image J software were utilized for quantification of NIRAF signal. Results: Thirty-one brain-dead deceased donor PTG procurements were performed by abdominal transplant surgeons. In the initial 8 deceased donors, a mean of 1.75 glands (±1.48 glands SD) per donor were recovered using the 4-gland in situ technique. Implementation of combined en bloc resection with ex vivo NIRAF imaging in 23 consecutive donors yielded a mean of 3.60 glands (±0.4 SD) recovered per donor (P < 0.0001). Quantification of NIRAF integrated density signal demonstrated >1-fold log difference in PTG (2.13 × 105 pixels) versus surrounding anterior neck structures (1.9 × 104 pixels; P < 0.0001). PTGs maintain distinct NIRAF signal from the time of recovery (1.88 × 105 pixels) up to 48 h post-procurement (1.55 × 105 pixels) in organ preservation cold storage (P = 0.34). Conclusions: The use of an en bloc surgical technique with ex vivo NIRAF imaging significantly enhances the identification and recovery of PTG from deceased donors.

Metastatic Donor-derived Malignancies Following Simultaneous Pancreas-kidney Transplant: Three Case Reports and Management Strategies.

Stopping immunosuppression in a transplant patient with donor-derived malignancy offers the theoretical benefit that reconstitution of the patient's immune system will allow "rejection" of the malignancy, as the malignancy also originates from allogeneic tissue. However, this option exists with the caveat that the patient's allograft(s) will likely be rejected too. In simultaneous pancreas-kidney (SPK) recipients, the normal continued functioning and possible absence of malignancy in either the unaffected kidney or pancreas further complicate this decision. METHODS: The charts of 3 patients with donor-derived metastatic malignancies after SPK were retrospectively reviewed in detail. We provide treatment and management recommendations based on successful outcomes and a review of the existing literature. RESULTS: Consistent with a broad review of the literature, in all 3 cases, complete immunosuppression cessation, removal of both grafts, and in 1 case treatment with an immune checkpoint inhibitor to augment the immune response was successful. One patient is doing well 1 year after successfully undergoing kidney retransplantation, while a second patient is active on the waitlist for SPK retransplantation after no evidence of metastatic disease for 2 years. CONCLUSION: The successful management of metastatic donor-derived malignancies requires allograft removal, immunosuppression cessation, and adjuvant therapy that includes occasional use of checkpoint inhibitors to augment the immune response.

Rapid Modification of Workflows and Fellow Staffing at a Single Transplant Center to Address the COVID-19 Crisis.

BACKGROUND: Although hospital systems have largely halted elective surgical practices in preparing their response to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, transplantation remains an essential and lifesaving surgical practice. To continue transplantation while protecting immunocompromised patients and health care workers, significant restructuring of normal patient care practice habits is required. METHODS: This is a nonrandomized, descriptive study of the abdominal transplant program at 1 academic center (University of California, San Francisco) and the programmatic changes undertaken to safely continue transplantations. Patient transfers, fellow use, and patient discharge education were identified as key areas requiring significant reorganization. RESULTS: The University of California, San Francisco abdominal transplant program took an early and aggressive approach to restructuring inpatient workflows and health care worker staffing. The authors formalized a coronavirus disease 2019 (COVID-19) transfer system to address patients in need of services at their institution while minimizing the risk of SARS-CoV-2 in their transplant ward and used technological approaches to provide virtual telehealth where possible. They also modified their transplant fellow staffing and responsibilities to develop an adequate backup system in case of potential exposures. CONCLUSION: Every transplant program is unique, and an individualized plan to adapt and modify standard clinical practices will be required to continue providing essential transplantation services. The authors' experience highlights areas of attention specific to transplant programs and may provide generalizable solutions to support continued transplantation in the COVID-19 era.

Identification of common genetic variants that account for transcript isoform variation between human populations.

In addition to the differences between populations in transcriptional and translational regulation of genes, alternative pre-mRNA splicing (AS) is also likely to play an important role in regulating gene expression and generating variation in mRNA and protein isoforms. Recently, the genetic contribution to transcript isoform variation has been reported in individuals of recent European descent. We report here results of an investigation of the differences in AS patterns between human populations. AS patterns in 176 HapMap lymphoblastoid cell lines derived from individuals of European and African ancestry were evaluated using the Affymetrix GeneChip Human Exon 1.0 ST Array. A variety of biological processes such as response to stimulus and transcription were found to be enriched among the differentially spliced genes. The differentially spliced genes also include some involved in human diseases that have different prevalence or susceptibility between populations. The genetic contribution to the population differences in transcript isoform variation was then evaluated by a genome-wide association using the HapMap genotypic data on single nucleotide polymorphisms (SNPs). The results suggest that local and distant genetic variants account for a substantial fraction of the observed transcript isoform variation between human populations. Our findings provide new insights into the complexity of the human genome as well as the health disparities between the two populations.

Impact of Immune-Modulatory Drugs on Regulatory T Cell.

Immunosuppression strategies that selectively inhibit effector T cells while preserving and even enhancing CD4FOXP3 regulatory T cells (Treg) permit immune self-regulation and may allow minimization of immunosuppression and associated toxicities. Many immunosuppressive drugs were developed before the identity and function of Treg were appreciated. A good understanding of the interactions between Treg and immunosuppressive agents will be valuable to the effective design of more tolerable immunosuppression regimens. This review will discuss preclinical and clinical evidence regarding the influence of current and emerging immunosuppressive drugs on Treg homeostasis, stability, and function as a guideline for the selection and development of Treg-friendly immunosuppressive regimens.