Second-Line Tisagenlecleucel or Standard Care in Aggressive B-Cell Lymphoma.

BACKGROUND: Patient outcomes are poor for aggressive B-cell non-Hodgkin's lymphomas not responding to or progressing within 12 months after first-line therapy. Tisagenlecleucel is an anti-CD19 chimeric antigen receptor T-cell therapy approved for diffuse large B-cell lymphoma after at least two treatment lines. METHODS: We conducted an international phase 3 trial involving patients with aggressive lymphoma that was refractory to or progressing within 12 months after first-line therapy. Patients were randomly assigned to receive tisagenlecleucel with optional bridging therapy (tisagenlecleucel group) or salvage chemotherapy and autologous hematopoietic stem-cell transplantation (HSCT) (standard-care group). The primary end point was event-free survival, defined as the time from randomization to stable or progressive disease at or after the week 12 assessment or death. Crossover to receive tisagenlecleucel was allowed if a defined event occurred at or after the week 12 assessment. Other end points included response and safety. RESULTS: A total of 322 patients underwent randomization. At baseline, the percentage of patients with high-grade lymphomas was higher in the tisagenlecleucel group than in the standard-care group (24.1% vs. 16.9%), as was the percentage with an International Prognostic Index score (range, 0 to 5, with higher scores indicating a worse prognosis) of 2 or higher (65.4% vs. 57.5%). A total of 95.7% of the patients in the tisagenlecleucel group received tisagenlecleucel; 32.5% of the patients in the standard-care group received autologous HSCT. The median time from leukapheresis to tisagenlecleucel infusion was 52 days. A total of 25.9% of the patients in the tisagenlecleucel group had lymphoma progression at week 6, as compared with 13.8% of those in the standard-care group. The median event-free survival in both groups was 3.0 months (hazard ratio for event or death in the tisagenlecleucel group, 1.07; 95% confidence interval, 0.82 to 1.40; P = 0.61). A response occurred in 46.3% of the patients in the tisagenlecleucel group and in 42.5% in the standard-care group. Ten patients in the tisagenlecleucel group and 13 in the standard-care group died from adverse events. CONCLUSIONS: Tisagenlecleucel was not superior to standard salvage therapy in this trial. Additional studies are needed to assess which patients may obtain the most benefit from each approach. (Funded by Novartis; BELINDA ClinicalTrials.gov number, NCT03570892.).

Cell Cycle-Mediated Regulation of Secondary Ig Diversification.

Secondary Ig diversification in B cells requires the deliberate introduction of DNA damage into the Ig genes by the enzyme activation-induced cytidine deaminase (AID) and the error-prone resolution of AID-induced lesions. These processes must be tightly regulated because they may lead to lymphomagenesis if they act on genes other than the Ig genes. Since B cells may limit secondary Ig diversification mechanisms during the cell cycle to minimize genomic instability, we restricted the activity of AID specifically to the G1 or S/G2 phase to investigate the cell cycle contribution to the regulation of somatic hypermutation, class switch recombination, and Ig gene conversion in human, murine, and avian B cells, respectively. The efficient induction of AID in different cell cycle phases allowed us for the first time, to our knowledge, to discriminate G1- from S/G2-specific events of regulation. We show that the processes of Ig gene conversion and C/G mutagenesis during somatic hypermutation can be achieved throughout the cell cycle, whereas A/T mutagenesis and class switch recombination require AID-mediated deamination in G1. Thus, AID activity in G1, but not in S/G2, leads to the efficient accomplishment of all mechanisms of secondary Ig diversification. Our findings refine the current state-of-the-art knowledge in the context of the regulation of secondary Ig diversification.

The impact of the COVID-19 pandemic on administrative eating disorder prevalence in the outpatient sector and on severity of anorexia nervosa.

The COVID-19 pandemic appears to have had a considerable impact on the mental health of children and adolescents, particularly regarding eating disorders. However, it remains unclear whether the pandemic affected only the frequency or also the severity of eating disorders. We examined potential pandemic-related changes in the administrative prevalence of eating disorders in the outpatient sector compared with other mental disorders using German statutory health insurance data for the age group 10 to 16 years. We also examined disorder severity of anorexia nervosa using data from the multicenter German Registry of Children and Adolescents with Anorexia Nervosa in the same age group. Our results showed a marked increase in the administrative prevalence of eating disorders (based on documented diagnoses) in the outpatient sector among girls but not among boys. A similar pattern was found for internalizing disorders, whereas the administrative prevalences of externalizing disorders decreased. Regarding the severity of anorexia nervosa among inpatients, we found no pandemic-related changes in body mass index standard deviation score at admission, body weight loss before admission, psychiatric comorbidities and psychopharmacological medication. Given the administrative prevalence increase in the outpatient sector, the lack of impact of the pandemic on the inpatient sector may also be partly due to a shift in healthcare utilization towards outpatient services during the pandemic. Thus, the higher number of children and adolescents requiring specialized and timely outpatient care may be a major concern under pandemic conditions.

Antibody response to a third SARS-CoV-2 vaccine dose in recipients of an allogeneic haematopoietic cell transplantation.

Allogeneic haematopoietic cell transplantation (allo-HCT) recipients show impaired antibody (Ab) response to a standard two-dose vaccination against severe acute respiratory syndrome coronavirus-2 and currently a third dose is recommended as part of the primary vaccination regimen. By assessing Ab titres 1 month after a third mRNA vaccine dose in 74 allo-HCT recipients we show sufficient neutralisation activity in 77% of the patients. Discontinuation of immunosuppression before the third vaccine led to serological responses in 50% of low responders to two vaccinations. Identifying factors that might contribute to better vaccine responses in allo-HCT recipients is critical to optimise current vaccination strategies.

Dissection of Barrier Dysfunction in Organoid-Derived Human Intestinal Epithelia Induced by Giardia duodenalis.

BACKGROUND & AIMS: The protozoa Giardia duodenalis is a major cause of gastrointestinal illness worldwide, but underlying pathophysiological mechanisms remain obscure, partly due to the absence of adequate cellular models. We aimed at overcoming these limitations and recapitulating the authentic series of pathogenic events in the primary human duodenal tissue by using the human organoid system. METHODS: We established a compartmentalized cellular transwell system with electrophysiological and barrier properties akin to duodenal mucosa and dissected the events leading to G. duodenalis-induced barrier breakdown by functional analysis of transcriptional, electrophysiological, and tight junction components. RESULTS: Organoid-derived cell layers of different donors showed a time- and parasite load-dependent leak flux indicated by collapse of the epithelial barrier upon G. duodenalis infection. Gene set enrichment analysis suggested major expression changes, including gene sets contributing to ion transport and tight junction structure. Solute carrier family 12 member 2 and cystic fibrosis transmembrane conductance regulator-dependent chloride secretion was reduced early after infection, while changes in the tight junction composition, localization, and structural organization occurred later as revealed by immunofluorescence analysis and freeze fracture electron microscopy. Functionally, barrier loss was linked to the adenosine 3',5'-cyclic monophosphate (cAMP)/protein kinase A-cAMP response element-binding protein signaling pathway. CONCLUSIONS: Data suggest a previously unknown sequence of events culminating in intestinal barrier dysfunction upon G. duodenalis infection during which alterations of cellular ion transport were followed by breakdown of the tight junctional complex and loss of epithelial integrity, events involving a cAMP/protein kinase A-cAMP response element-binding protein mechanism. These findings and the newly established organoid-derived model to study G. duodenalis infection may help to explore new options for intervening with disease and infection, in particular relevant for chronic cases of giardiasis.

Association of Host Factors With Antibody Response to Seasonal Influenza Vaccination in Allogeneic Hematopoietic Stem Cell Transplant Patients.

BACKGROUND: Influenza vaccination efficacy is reduced after hematopoietic stem cell transplantation (HSCT) and patient factors determining vaccination outcomes are still poorly understood. METHODS: We investigated the antibody response to seasonal influenza vaccination in 135 HSCT patients and 69 healthy volunteers (HVs) in a prospective observational multicenter cohort study. We identified patient factors associated with hemagglutination inhibition titers against A/California/2009/H1N1, A/Texas/2012/H3N2, and B/Massachusetts/2012 by multivariable regression on the observed titer levels and on seroconversion/seroprotection categories for comparison. RESULTS: Both regression approaches yielded consistent results but regression on titers estimated associations with higher precision. HSCT patients required 2 vaccine doses to achieve average responses comparable to a single dose in HVs. Prevaccination titers were positively associated with time after transplantation, confirming that HSCT patients can elicit potent antibody responses. However, an unrelated donor, absolute lymphocyte counts below the normal range, and treatment with calcineurin inhibitors lowered the odds of responding. CONCLUSIONS: HSCT patients show a highly heterogeneous vaccine response but, overall, patients benefited from the booster shot and can acquire seroprotective antibodies over the years after transplantation. Several common patient factors lower the odds of responding, urging identification of additional preventive strategies in the poorly responding groups. CLINICAL TRIALS REGISTRATION: NCT03467074.

LIKE SEX4 1 Acts as a ß-Amylase-Binding Scaffold on Starch Granules during Starch Degradation.

In Arabidopsis (Arabidopsis thaliana) leaves, starch is synthesized during the day and degraded at night to fuel growth and metabolism. Starch is degraded primarily by ß-amylases, liberating maltose, but this activity is preceded by glucan phosphorylation and is accompanied by dephosphorylation. A glucan phosphatase family member, LIKE SEX4 1 (LSF1), binds starch and is required for normal starch degradation, but its exact role is unclear. Here, we show that LSF1 does not dephosphorylate glucans. The recombinant dual specificity phosphatase (DSP) domain of LSF1 had no detectable phosphatase activity. Furthermore, a variant of LSF1 mutated in the catalytic cysteine of the DSP domain complemented the starch-excess phenotype of the lsf1 mutant. By contrast, a variant of LSF1 with mutations in the carbohydrate binding module did not complement lsf1 Thus, glucan binding, but not phosphatase activity, is required for the function of LSF1 in starch degradation. LSF1 interacts with the ß-amylases BAM1 and BAM3, and the BAM1-LSF1 complex shows amylolytic but not glucan phosphatase activity. Nighttime maltose levels are reduced in lsf1, and genetic analysis indicated that the starch-excess phenotype of lsf1 is dependent on bam1 and bam3 We propose that LSF1 binds ß-amylases at the starch granule surface, thereby promoting starch degradation.

Resource utilization for chimeric antigen receptor T cell therapy versus autologous hematopoietic cell transplantation in patients with B cell lymphoma.

CD19-directed chimeric antigen receptor T cells (CAR-T) have emerged as a highly efficacious treatment for patients with relapsed/refractory (r/r) B cell lymphoma (BCL). The value of CAR-T for these patients is indisputable, but one-off production costs are high, and little is known about the ancillary resource consumption associated with CAR-T treatment. Here, we compared the resource use and costs of CAR-T treatment with high-dose chemotherapy followed by autologous stem cell transplantation (ASCT) for patients with r/r BCL. Standard operating procedures were used to develop a process model in ClipMedPPM, which comprises all activities and processes to sustain or generate treatment components that together constitute a treatment path. The software allows a graphic representation and the use of standardized linguistic elements for comparison of different treatment paths. Detailed processes involved in CAR-T treatments (n = 1041 processes) and in ASCT (n = 1535) were analyzed for time consumption of treatment phases and personnel. Process costs were calculated using financial controlling data. CAR-T treatment required ~ 30% less staff time than ASCT (primarily nursing staff) due to fewer chemotherapy cycles, less outpatient visits, and shorter hospital stays. For CAR-T, production costs were ~ 8 × higher, but overall treatment time was shorter compared with ASCT (30 vs 48 days), and direct labor and overhead costs were 40% and 10% lower, respectively. Excluding high product costs, CAR-T uses fewer hospital resources than ASCT for r/r BCL. Fewer hospital days for CAR-T compared to ASCT treatment and the conservation of hospital resources are beneficial to patients and the healthcare system.

Dynamics of Inflammatory and Neurodegenerative Biomarkers after Autologous Hematopoietic Stem Cell Transplantation in Multiple Sclerosis.

Autologous hematopoietic stem cell transplantation (aHSCT) is a highly efficient treatment of multiple sclerosis (MS), and hence it likely normalizes pathological and/or enhances beneficial processes in MS. The disease pathomechanisms include neuroinflammation, glial cell activation and neuronal damage. We studied biomarkers that in part reflect these, like markers for neuroinflammation (C-X-C motif chemokine ligand (CXCL) 9, CXCL10, CXCL13, and chitinase 3-like 1 (CHI3L1)), glial perturbations (glial fibrillary acidic protein (GFAP) and in part CHI3L1), and neurodegeneration (neurofilament light chain (NfL)) by enzyme-linked immunosorbent assays (ELISA) and single-molecule array assay (SIMOA) in the serum and cerebrospinal fluid (CSF) of 32 MS patients that underwent aHSCT. We sampled before and at 1, 3, 6, 12, 24 and 36 months after aHSCT for serum, as well as before and 24 months after aHSCT for CSF. We found a strong increase of serum CXCL10, NfL and GFAP one month after the transplantation, which normalized one and two years post-aHSCT. CXCL10 was particularly increased in patients that experienced reactivation of cytomegalovirus (CMV) infection, but not those with Epstein-Barr virus (EBV) reactivation. Furthermore, patients with CMV reactivation showed increased Th1 phenotype in effector memory CD4+ T cells. Changes of the other serum markers were more subtle with a trend for an increase in serum CXCL9 early post-aHSCT. In CSF, GFAP levels were increased 24 months after aHSCT, which may indicate sustained astroglia activation 24 months post-aHSCT. Other CSF markers remained largely stable. We conclude that MS-related biomarkers indicate neurotoxicity early after aHSCT that normalizes after one year while astrocyte activation appears increased beyond that, and increased serum CXCL10 likely does not reflect inflammation within the central nervous system (CNS) but rather occurs in the context of CMV reactivation or other infections post-aHSCT.

Long-Term Follow-Up of Antibody Titers Against Measles, Mumps, and Rubella in Recipients of Allogenic Hematopoietic Cell Transplantation.

Outbreaks of viral infections, such as measles, are regularly observed and pose a serious threat to recipients of allogeneic hematopoietic cell transplantation (HCT). The questions of how long cellular and humoral protective host immunity persists, and whether donor immunity can be transferred has not been clarified. Here we present a retrospective analysis of humoral immunity-serial antibody titers against measles, mumps, and rubella-in 331 patients who underwent allogeneic HCT at our single center between 2002 and 2015. Associations between the loss of protective antibody levels and clinical patient characteristics and transplantation parameters were examined. In general, antibody protection against measles persisted longer, with 72% of patients maintaining sufficient titers at 5 years post-HCT even without revaccination, while at that time only 65% and 50% of patients had protective immunity against rubella and mumps, respectively. The great majority of donors were seropositive for all 3 viruses; however, it appeared that donor humoral immunity could not be transferred and had no impact on post-HCT serostatus. Rather, the most relevant factor for persistent protective antibody titers against measles and rubella was whether patients were born before the introduction of the respective vaccine and thus were immunized by the wild-type disease-inducing virus instead of the vaccine. Moreover, the presence of moderate and severe chronic graft-versus-host disease (GVHD) was associated with more rapid loss of immune protection. In contrast, underlying disease, intensity of the conditioning regimen, use of antithymocyte globulin, age, and graft source had no influence on antibody titers. Overall, our findings suggest that the majority of antibodies against measles, mumps, and rubella originate from residual host cells, whereas donor immune status appears to have no influence on antibody protection post-HCT.

Microbiologically documented infections after adult allogeneic hematopoietic cell transplantation: A 5-year analysis within the Swiss Transplant Cohort study.

BACKGROUND: Infections are an important complication after allogeneic hematopoietic cell transplantation (allo-HCT). The present study aimed at determining the landscape of infections occurring in a large cohort of allo-HCT patients, as well as associated risk factors for infections and for one-year non-relapse mortality. METHODS: This is a retrospective cohort study using STCS and EBMT databases to assess the one-year incidence rate of infection, as well as risk factors for infections and for one-year non-relapse mortality among adult allo-HCT patients transplanted between 2010 and 2014 in Switzerland. Univariable and multivariable quasi-Poisson and multivariable Cox regression models were used. RESULTS: Of 553 patients included, 486 had an infection with a global incidence rate of 3.66 infections per patient-year. Among a total of 1534 infections analyzed, viral infections were predominant (n = 1138, 74.2%), followed by bacterial (n = 343, 22.4%) and fungal (n = 53, 3.5%) infections. At one year, the cumulative incidence of relapse and non-relapse mortality was 26% and 16%, respectively. 195 (35.3%) of patients had at least one episode of severe graft-versus-host-disease (GvHD). A center effect was observed, and underlying disease, donor type, cytomegalovirus serological constellation, and GvHD were also associated with the incidence rate of infections. There was an increased risk for one-year non-relapse mortality associated with all pathogens, specifically within two months of infection, and this remained true beyond 2 months of a fungal infection. CONCLUSION: Despite advances to limit infections in this population, they still occur in most allo-HCT patients with a major impact on survival at 1 year.

Modeling Chronic Graft-versus-Host Disease in MHC-Matched Mouse Strains: Genetics, Graft Composition, and Tissue Targets.

Graft-versus-host disease (GVHD) remains a major complication of allogeneic hematopoietic cell transplantation. Acute GVHD (aGVHD) results from direct damage by donor T cells, whereas the biology of chronic GVHD (cGVHD) with its autoimmune-like manifestations remains poorly understood, mainly because of the paucity of representative preclinical models. We examined over an extended time period 7 MHC-matched, minor antigen-mismatched mouse models for development of cGVHD. Development and manifestations of cGVHD were determined by a combination of MHC allele type and recipient strain, with BALB recipients being the most susceptible. The C57BL/6 into BALB.B combination most closely modeled the human syndrome. In this strain combination moderate aGVHD was observed and BALB.B survivors developed overt cGVHD at 6 to 12 months affecting eyes, skin, and liver. Naïve CD4+ cells caused this syndrome as no significant pathology was induced by grafts composed of purified hematopoietic stem cells (HSCs) or HSC plus effector memory CD4+ or CD8+ cells. Furthermore, co-transferred naïve and effector memory CD4+ T cells demonstrated differential homing patterns and locations of persistence. No clear association with donor Th17 cells and the phenotype of aGVHD or cGVHD was observed in this model. Donor CD4+ cells caused injury to medullary thymic epithelial cells, a key population responsible for negative T cell selection, suggesting that impaired thymic selection was an underlying cause of the cGVHD syndrome. In conclusion, we report for the first time that the C57BL/6 into BALB.B combination is a representative model of cGVHD that evolves from immunologic events during the early post-transplant period.

Mobilization of Hematopoietic Progenitor Cells with Standard- or Reduced-Dose Filgrastim after Vinorelbine in Multiple Myeloma Patients: A Randomized Prospective Single-Center Phase II Study.

Vinorelbine combined with filgrastim at a dose of 10 µg/kg of body weight (BW) per day is a reliable and well-tolerated regimen for mobilization of hematopoietic progenitor cells (HPCs) in patients with multiple myeloma. This prospective, randomized, phase II study was initiated to assess the feasibility of a reduced filgrastim dosage. Vinorelbine was combined with either standard-dose filgrastim (10 µg/kg BW per day) or reduced-dose filgrastim (5 µg/kg BW per day). Leukapheresis sessions were planned to start at day 8 and were continued until the predefined target amount of 4 × 106 HPCs/kg BW was collected. The study demonstrated the feasibility of vinorelbine combined with reduced daily filgrastim with a mean of 1.29 leukapheresis sessions necessary per patient (95% confidence interval, .95 to 1.7). All patients could start leukapheresis as planned at day 8, and the collection success rate was 100% for the whole patient collective after a maximum of 2 leukapheresis sessions. No statistically significant differences with regard to the amount of HPCs collected between the 2 groups were observed (P = .99). Accordingly, no differences were seen with regard to length of hospitalization for autotransplant (P = .34) and duration of neutrophil (P = .93) and platelet engraftment (P = .42). Patients receiving reduced-dose filgrastim reported significantly lower peak pain values in a numeric analogue scale (P = .01), and the costs were significantly lower than in patients undergoing standard-dose chemomobilization (P = .001). Vinorelbine 35 mg/m2 plus filgrastim 5 µg/kg BW once per day until completion of HPC collection is feasible and appears to be advantageous with respect to the severity of pain intensity and treatment costs.

Allogeneic hematopoietic cell transplantation in patients with GATA2 deficiency-a case report and comprehensive review of the literature.

Recently, an immunodeficiency syndrome caused by guanine-adenine-thymine-adenine 2 (GATA2) deficiency has been described. The syndrome is characterized by (i) typical onset in early adulthood, (ii) profound peripheral blood cytopenias of monocytes, B lymphocytes, and NK cells, (iii) distinct susceptibility to disseminated non-tuberculous mycobacterial (NTM) and other opportunistic infections (particularly human papillomavirus), and (iv) a high risk of developing hematologic malignancies (myelodysplastic syndromes (MDS); acute myeloid leukemias (AML)). Considerable clinical heterogeneity exists among patients with GATA2 deficiency, but once infectious symptoms occur or MDS/AML arises, survival declines significantly. Allogeneic hematopoietic cell transplantation (HCT) currently provides the only curative treatment option for both MDS/AML and dysfunctional immunity with life-threatening opportunistic infections. Strategies regarding timing of allogeneic HCT, antimicrobial prophylaxis and treatment, intensity of the preparative regimen, and optimal donor and graft source have not been clearly defined due to the rarity of the disease. Here, we provide a comprehensive analysis of the available literature and published case reports on the use of allogeneic HCT in patients with GATA2 deficiency. In addition, a case of a young woman with GATA2 deficiency, who developed an immune reconstitution inflammatory syndrome in her mycobacterial skin lesions post allogeneic HCT is presented and illustrates distinct problems encountered in this disease context.

Blood Stem Cell Activity Is Arrested by Th1-Mediated Injury Preventing Engraftment following Nonmyeloablative Conditioning.

T cells are widely used to promote engraftment of hematopoietic stem cells (HSCs) during an allogeneic hematopoietic cell transplantation. Their role in overcoming barriers to HSC engraftment is thought to be particularly critical when patients receive reduced doses of preparative chemotherapy and/or radiation compared with standard transplantations. In this study, we sought to delineate the effects CD4+ cells on engraftment and blood formation in a model that simulates clinical hematopoietic cell transplantation by transplanting MHC-matched, minor histocompatibility-mismatched grafts composed of purified HSCs, HSCs plus bulk T cells, or HSCs plus T cell subsets into mice conditioned with low-dose irradiation. Grafts containing conventional CD4+ T cells caused marrow inflammation and inhibited HSC engraftment and blood formation. Posttransplantation, the marrows of HSCs plus CD4+ cell recipients contained IL-12-secreting CD11c+ cells and IFN-γ-expressing donor Th1 cells. In this setting, host HSCs arrested at the short-term stem cell stage and remained in the marrow in a quiescent cell cycling state (G0). As a consequence, donor HSCs failed to engraft and hematopoiesis was suppressed. Our data show that Th1 cells included in a hematopoietic allograft can negatively impact HSC activity, blood reconstitution, and engraftment of donor HSCs. This potential negative effect of donor T cells is not considered in clinical transplantation in which bulk T cells are transplanted. Our findings shed new light on the effects of CD4+ T cells on HSC biology and are applicable to other pathogenic states in which immune activation in the bone marrow occurs such as aplastic anemia and certain infectious conditions.

Response to Tyrosine Kinase Inhibitors in Myeloproliferative Neoplasia with 8p11 Translocation and CEP110-FGFR1 Rearrangement.

This brief communication reports on a patient with an exceedingly rare "8p11 (eight-p-eleven) myeloproliferative syndrome" (EMS) with CEP110-FGFR1 rearrangement who responded to treatment with the multi-tyrosine kinase inhibitor (TKI) dasatinib. Dasatinib improved quality of life substantially by increasing blood counts and reducing the need for transfusions. This report demonstrates that the second-generation TKI may provide a therapeutic option for elderly and frail EMS patients who cannot be offered aggressive therapy, including allogeneic hematopoietic cell transplantation. The Oncologist 2017;22:480-483.

Autologous apoptotic cells preceding transplantation enhance survival in lethal murine graft-versus-host models.

Acute graft-versus-host disease (GVHD) is induced by alloreactivity of donor T cells toward host antigens presented on antigen-presenting cells (APCs). Apoptotic cells are capable of inducing tolerance by altering APC maturation. Apoptosis can be induced by extracorporeal photopheresis (ECP). We demonstrate that the use of ECP as a prophylaxis prior to conditioning significantly improves survival (P < .0001) after bone marrow transplantation (BMT) by inhibiting the initiation phase of acute GVHD in a murine BMT model. ECP-treated autologous splenocytes resulted in immune tolerance in the host, including reduced dendritic cell activation with decreased nuclear factor-κB engagement, increased regulatory T-cell (Treg) numbers with enhanced expression of cytolytic T lymphocyte-associated antigen 4, potentiating their suppressive function. The protective effect required host production of interleukin-10 and host Tregs. Conventional T cells that entered this tolerant environment experienced reduced proliferation, as well as a reduction of tissue homing and expression of activation markers. The induction of this tolerant state by ECP was obviated by cotreatment with lipopolysaccharide, suggesting that the inflammatory state of the recipient prior to treatment would play a role in potential clinical translation. The use of prophylactic ECP may provide an alternative and safe method for immunosuppression in the bone marrow transplant setting.