GVHD: a continuing barrier to the safety of allogeneic transplantation

Advances in the ocular complications after hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) has benefited an increasing number of patients with hematological disease in the clinic. It is a curative therapy for malignant and nonmalignant hematological diseases. With the advancement and further clinical application of HSCT in recent years, the life expectancy of patients has increased, but complications have become more common. The occurrence of ocular complications is receiving increasing attention because they can seriously affect the quality of life of patients. Ocular complications require increased attention from clinicians because of their negative impact on patients and increasing incidence. Most of recent reports on posttransplant ocular complications involve ocular manifestations of graft-versus-host disease (GVHD), and a few ocular complications that do not originate from GVHD have also been reported. This review summarizes the diagnosis, scoring criteria, pathophysiology, and clinical manifestations of and common therapies for ocular graft-versus-host disease(oGVHD) after HSCT, and includes a description of some rare cases and novel therapies.

Recent advances in the diagnosis and management of acute myocardial infarction

With the discovery of new biomarkers for the early detection of acute myocardial infarction (AMI), advancements in valid medication, and percutaneous coronary intervention (PCI), the overall prognosis of AMI has improved remarkably. Nevertheless, challenges remain which require more difficult work to overcome. Novel diagnostic and therapeutic techniques include new AMI biomarkers, hypothermia therapy, supersaturated oxygen (SSO 2 ) therapy, targeted anti-inflammatory therapy, targeted angiogenesis therapy, and stem cell therapy. With these novel methods, we believe that the infarction size after AMI will decrease, and myocardial injury-associated ventricular remodeling may be avoided. This review focuses on novel advances in the diagnosis and management of AMI.

The ocular graft-versus-host disease: the path from current knowledge to future managements

BACKGROUND

Graft-versus-host disease (GVHD) is one of the major complications of allogenic haematopoietic stem cell transplantation (HSCT). The manifestation of ocular GVHD (oGVHD) is variable and may involve cornea, lacrimal gland, conjunctiva, eyelid, and/or nasolacrimal duct. We reviewed and summarized the current managements of oGVHD with specific focus on the emerging therapeutic advances.

METHODS

PubMed, Web of Science, and Google Scholar were searched for relevant literatures published within 20 years. Keywords used included "Graft-Versus-Host Disease", "GVHD", "ocular", "ocular surface", "ocular GVHD", "oGVHD", "dry eye", "keratitis", etc. RESULTS: Current managements of oGVHD can be classified into topical immunosuppressants, local tear-preservatory treatments, local non-pharmacological/surgical interventions, and systemic treatments. Additionally, some innovative therapies with promising treatment effects have been proposed, including topical target therapies, epitheliotrophic and neurotrophic treatments, recombinant DNase eye drops, mesenchymal stromal cell injection, and more.

CONCLUSIONS

Clinical managements of oGVHD are administered in a symptom-based, stepwise manner. The advances in innovative therapies may help improve clinical outcomes, and it is essential that physicians stay updated with these novel treatment options.

Risk Factors for the Incidence of and the Mortality due to Post-Transplant Lymphoproliferative Disorder after Hematopoietic Cell Transplantation

Post-transplant lymphoproliferative disorder (PTLD) is a potentially serious complication that occurs following hematopoietic cell transplantation (HCT), in which B cells transformed by Epstein-Barr virus (EBV) proliferate uncontrollably. It is unknown whether risk factors for the incidence of PTLD are identical to those for mortality due to PTLD, a clinically more important outcome. We sought to determine the risk factors influencing the incidence of PTLD and those influencing mortality due to PTLD in a cohort of 1184 allogenic HCT recipients. All patients were predisposed to PTLD, because their graft-versus-host disease (GVHD) prophylaxis included antithymocyte globulin. The overall PTLD incidence was 9.0%, and mortality due to PTLD was 1.1%. In multivariate analysis, risk factors for PTLD incidence include donor+/recipient- (D+/R-) EBV serostatus (subhazard ratio [SHR], 3.3; P = .002), use of a donor other than an HLA-matched sibling donor (non-MSD) (SHR, 1.7; P = .029), receipt of total body irradiation (TBI; SHR, 3.3; P = .008), and the absence of GVHD (SHR, 3.3; P < .001). The sole risk factor for mortality due to PTLD among all patients was D+/R- serostatus (SHR, 5.8; P = .022). Risk factors for mortality due to PTLD among patients who developed PTLD were use of a bone marrow (BM) graft (compared with peripheral blood stem cells [PBSCs]; SHR, 22.8; P < .001) and extralymphatic involvement (SHR, 14.6; P < .001). Interestingly, whereas the absence of GVHD was a risk factor for PTLD incidence, there was a trend toward the presence of GVHD as a risk factor for PTLD mortality (SHR, 4.2; P = .093). Likewise, whereas use of a BM graft was a risk factor for PTLD mortality, there was a trend toward use of a PBSC graft as a risk factor for PTLD incidence (SHR, 0.44; P = .179). Some risk factors for the incidence of PTLD are identical to the risk factors for mortality due to PTLD (ie, D+/R- serostatus), whereas other risk factors are disparate. Specifically, TBI was identified as a risk factor for PTLD incidence but not for PTLD mortality; the absence of GVHD was a risk factor for PTLD incidence, whereas the presence of GVHD was possibly a risk factor for PTLD mortality; and receipt of a PBSC graft was possibly a risk factor for PTLD incidence, whereas receipt of a BM graft was a risk factor for PTLD mortality.

Analysis of the Whole CDR3 T Cell Receptor Repertoire after Hematopoietic Stem Cell Transplantation in 2 Clinical Cohorts

A major cause of morbidity and mortality for patients who undergo hematologic stem cell transplantation (HSCT) is acute graft-versus-host disease (aGVHD), a mostly T cell-mediated disease. Examination of the T cell receptor (TCR) repertoire of HSCT recipients and the use of next-generation nucleotide sequencing have raised the question of whether features of TCR repertoire reconstitution might reproducibly associate with aGVHD. We hypothesized that the peripheral blood TCR repertoire of patients with steroid-nonresponsive aGVHD would be less diverse. We also hypothesized that patients with GVHD who shared HLA might also share common clones at the time of GVHD diagnosis, thereby potentially providing potential clinical indicators for treatment stratification. We further hypothesized that HSCT recipients with the same HLA mismatch might share a more similar TCR repertoire based on a potentially shared focus of alloreactive responses. We studied 2 separate patient cohorts and 2 separate platforms for measuring TCR repertoire. The first cohort of patients was from a multicenter Phase III randomized double-blinded clinical trial of patients who developed aGVHD (NCT01002742). The second cohort comprised samples from biobanks from 2 transplantation centers and the Center for International Blood and Marrow Transplant Research of patients who underwent mismatched HSCT. There were no statistically significant differences in the TCR diversity of steroid responders and nonresponders among patients with aGVHD on the day of diagnosis. Most clones in the repertoire were unique to each patient, but a small number of clones were found to be both exclusive to and shared among aGVHD nonresponders. We were also able to show a strong correlation between the presence of Vβ20 and Vβ29 and steroid responsiveness. Using the Bhattacharya coefficient, those patients who shared the same HLA mismatch were shown to be no more similar to one another than to those who had a completely different mismatch. Using 2 separate clinical cohorts and 2 separate platforms for analyzing the TCR repertoire, we have shown that the sampled human TCR repertoire is largely unique to each patient but contains glimmers of common clones of subsets of clones based on responsiveness to steroids in aGVHD on the day of diagnosis. These studies are informative for future strategies to assess for reproducible TCR responses in human alloreactivity and possible markers of GVHD responsiveness to therapy.

Activation of the DR3-TL1A Axis in Donor Mice Leads to Regulatory T Cell Expansion and Activation With Reduction in Graft-Versus-Host Disease

Death receptor 3 (DR3) is a tumor necrosis factor receptor superfamily member (TNFRSF25), which is minimally expressed on resting conventional T cells (though readily inducible upon cell activation), yet highly expressed on resting FoxP3⁺ regulatory T cells (Treg). We recently demonstrated that activation of DR3 with an agonistic antibody (4C12) leads to selective expansion and activation of Treg in healthy mice and suppression of graft-versus-host disease (GVHD) in recipient mice when donor mice are treated. However, given the long antibody half-life and concomitant safety concerns, along with the lack of a humanized agonistic antibody to DR3, both human and murine fusion proteins incorporating the natural DR3 ligand TL1A (TL1A-Ig) have been developed. Herein, we show that DR3 activation with 4C12 or with TL1A-Ig, with or without the addition of low dose IL-2 to the treatment regimen, led to a significant expansion of murine Treg in spleen, lymph nodes, and peripheral blood. Bioluminescent imaging revealed peak Treg expansion around day 7-8, with return to near baseline after 2-3 weeks. In addition to expansion, all DR3 agonist treatment regimens led to increased activation of Tregs, with significant upregulation of the activation markers ICOS, KLRG-1, PD-1, and CD103, and the proliferation marker Ki-67. The near absence of activated Treg populations in control treated spleens was also detected on tSNE analysis of flow cytometry data. Subtly different patterns of splenic Treg activation by the different DR3 agonists were noted in both tSNE analysis of flow cytometry data and RNA-sequencing analysis. However, upregulation of gene transcripts which play important roles in cell proliferation, trafficking, activation, and effector function were observed regardless of the DR3 agonist treatment regimen used. In the major MHC-mismatch model of hematopoietic cell transplantation, DR3 agonist-mediated expansion and activation of Tregs in donor mice led to a significant improvement in GVHD in recipient mice. These data provide important preclinical information regarding the outcome of DR3 activation with an agonistic antibody or natural ligand and provide insight into the therapeutic use of this approach to reduce GVHD in recipients and improve outcomes of hematopoietic cell transplantation.

Stem Cell Applications for Treatment of Cancer and Autoimmune Diseases: Its Promises, Obstacles, and Future Perspectives

Since the original discovery of stem cells, a new era of promising results has emerged in the clinical application of stem cells for the treatment of several important diseases, including cancer and autoimmune diseases. The plentiful research on stem cells during the past decades has provided significant information on the developmental, morphological, and physiological processes that govern tissue and organ formation, maintenance, and regeneration; cellular differentiation; molecular processes; and tissue homeostasis. In this review, we present the history of the use of stem cells in different clinical applications. Furthermore, we discuss the various therapeutic options for stem cells in cancer, followed by the role of stem cells in the treatment of autoimmune disorders. Additionally, we highlight the risks of and obstacles to the application of stem cells in clinical practice. Ultimately, we show future perspectives in stem cell use, with an aim to improve the clinical usefulness of stem cells.

IL-7 Is the Limiting Homeostatic Factor that Constrains Homeostatic Proliferation of CD8+ T Cells after Allogeneic Stem Cell Transplantation and Graft-versus-Host Disease

Immune reconstitution after allogeneic hematopoietic stem cell transplantation relies primarily on homeostatic proliferation (HP) of mature T lymphocytes, but this process is typically impaired during graft-versus-host disease (GVHD). We previously showed that low IL-7 levels combined with lack of dendritic cell (DC) regeneration constrain CD4⁺ T cell HP during GVHD. However, it is not clear whether these alterations to the peripheral CD4⁺ T cell niche also contribute to impair CD8⁺ T cell regeneration during GVHD. We found that IL-7 therapy was sufficient for restoring CD8⁺ T cell HP in GVHD hosts while forcing DC regeneration with Flt3-L had only a modest effect on CD8⁺ T cell HP in IL-7 treated mice. Using bone marrow chimeras, we showed that HP of naïve CD8⁺ T cells is primarily regulated by MHC class I on radio-resistant stromal cells, yet optimal recovery of CD8⁺ T cell counts still requires expression of MHC class I on both radio-resistant and radio-sensitive hematopoietic cells. Thus, IL-7 level is the primary limiting factor that constrains naïve CD8⁺ T cell HP during GVHD, and accessibility of MHC class I on stromal cells explains how IL-7 therapy, as a single agent, can induce robust CD8 ⁺ T cell HP in the absence of DCs.

Protective effect of neutralizing anti-IL-18α monoclonal antibody on a mouse model of acute graft-versus-host disease

Graft-versus-host disease (GVHD) is a devastating complication of hematopoietic stem cell transplantation (HSCT), and is characterized by systemic inflammation and tissue damage in multiple organs, such as the liver and small intestine. Interleukin-18 (IL-18), an important pro-inflammatory cytokine, is elevated during the course of acute GVHD (aGVHD), and is associated with the severe clinical manifestations of the disease. The biological activity of IL-18 is based on its interaction with the IL-18 receptor (IL-18R) expressed in a variety of cells. The aim of this study was to assess whether blocking the interaction of IL-18 with IL-18R by the anti-IL‑18Rα antibody could attenuate the severity of aGVHD. We used a well-established mouse bone marrow transplantation (BMT) model (B6→BALB/c) to block the IL-18/IL-18R interaction by a neutralizing monoclonal antibody (mAb) against murine IL-18Rα. Administration of anti-IL-18Rα mAb had a significant protective effect on the clinical and pathologic manifestations of aGVHD, resulting in a markedly improved survival rate, modified inflammatory response and decreased tissue damage. Interfering with IL-18/IL-18R interaction affected levels of Th1, Th2 and Th17 subsets in the peripheral blood of the aGVHD animals. Additionally, it led to decreased tissue expression of IL-18 and apoptosis-associated molecules (Fas and FasL), and lower phosphorylation levels of p38MAPK in the liver and small intestine. These changes coincided with the decrease in cell apoptosis in aGVHD target organs. Thus, anti‑IL-18Rα therapy may, therefore, represent a new therapeutic interference approach for treating aGVHD.

Various forms of tissue damage and danger signals following hematopoietic stem-cell transplantation

Hematopoietic stem-cell transplantation (HSCT) is the most potent curative therapy for many malignant and non-malignant disorders. Unfortunately, a major complication of HSCT is graft-versus-host disease (GVHD), which is mediated by tissue damage resulting from the conditioning regimens before the transplantation and the alloreaction of dual immune components (activated donor T-cells and recipient’s antigen-presenting cells). This tissue damage leads to the release of alarmins and the triggering of pathogen-recognition receptors that activate the innate immune system and subsequently the adaptive immune system. Alarmins, which are of endogenous origin, together with the exogenous pathogen-associated molecular patterns (PAMPs) elicit similar responses of danger signals and represent the group of damage-associated molecular patterns (DAMPs). Effector cells of innate and adaptive immunity that are activated by PAMPs or alarmins can secrete other alarmins and amplify the immune responses. These complex interactions and loops between alarmins and PAMPs are particularly potent at inducing and then aggravating the GVHD reaction. In this review, we highlight the role of these tissue damaging molecules and their signaling pathways. Interestingly, some DAMPs and PAMPs are organ specific and GVHD-induced and have been shown to be interesting biomarkers. Some of these molecules may represent potential targets for novel therapeutic approaches.

Population pharmacokinetics and individualized dosage prediction of cyclosporine in allogeneic hematopoietic stem cell transplant patients

BACKGROUND

Cyclosporine (CsA), a potent immunosuppressive agent used to prevent rejection, is characterized by large individual variability. The purpose of this study was to explore the pharmacokinetic characteristics of CsA and establish a CsA population pharmacokinetic model that could be used for personalized therapy in allogeneic hematopoietic stem cell transplant (allo-HSCT) patients.

METHODS

Clinical data were obtained from 117 allo-HSCT patients. The data analysis was performed using NONMEM software. A first-order conditional estimation with interaction (FOCE-I) method within NONMEM was used to estimate the parameters. The covariates, including demographics, hematological indices, biochemical levels, concurrent drugs, and genetic polymorphisms of CYP3A4, CYP3A5, and ABCB1, were evaluated quantitatively. The stability of the final model was validated by a nonparametric bootstrap procedure.

RESULTS

A total of 1,571 observed concentrations were collected. A 1-compartment model with first-order absorption and elimination adequately described the pharmacokinetics of CsA. The typical values for clearance (CL), volume of distribution (V), and bioavailability were 29.6 L/hr, 605 L, and 0.619, respectively. The interindividual variability of these parameters was 20.4, 66.1, and 30.4%, respectively. The residual error was 31.4% and 23.7 ng/mL. The duration of CsA therapy, hematocrit, antifungal agent administration, triglycerides, and weight were identified as the main covariates that influenced CL, and hematocrit had a significant effect on V. The internal validation showed that the final model was stable and accurate.

CONCLUSIONS

This study established a population pharmacokinetic model of CsA in allo-HSCT patients that could provide the foundation for personalized use of CsA in the clinic.

Cellular immune function monitoring after allogeneic haematopoietic cell transplantation: evaluation of a new assay

Managing the patient's immune system after haematopoietic cell transplantation (HCT) is a challenge, mainly in the unstable period immediately after the transplant. Currently there is no standardized non-invasive diagnostic tool for the evaluation of immunological complications such as graft-versus-host disease (GVHD) and for managing the cellular immune function of the transplant recipient. The ImmuKnow assay for cellular immune function monitoring has been incorporated successfully into the clinical follow-up routine of solid organ transplant recipients. This study aims to explore the relevance and potential contribution of immune monitoring using the assay in the setting of HCT. We found that ImmuKnow-level measurement can distinguish between states of immune function quiescence and between events of acute GVHD. ImmuKnow levels were significantly higher in patients going through GVHD than the levels measured for the same patients during immunological stability. Moreover, we demonstrate a patient case where longitudinal monitoring using the ImmuKnow assay provided a trustworthy depiction of the patient's cellular immune function post-HCT. In conclusion, we provide evidence for the potential contribution of the ImmuKnow assay for longitudinal individualized cellular immune function monitoring of patients following HCT. Further studies are necessary in order to establish the optimal practice for utilizing the assay for this purpose.

A distinct evolution of the T-cell repertoire categorizes treatment refractory gastrointestinal acute graft-versus-host disease

Steroid refractory gastrointestinal (GI) acute graft-versus-host disease (aGVHD) is a major cause of mortality in hematopoietic stem cell transplantation (HCT) without immune markers to establish a diagnosis or guide therapy. We found that T-cell receptor β (TCRβ) complementarity-determining region 3 repertoire sequencing reveals patterns that could eventually serve as a disease biomarker of T-cell alloreactivity in aGVHD. We identified T-cell clones in GI biopsies in a heterogeneous group of 15 allogeneic HCT patients with GI aGVHD symptoms. Seven steroid-refractory aGVHD patients showed a more conserved TCRβ clonal structure between different biopsy sites in the GI tract than 8 primary therapy-responsive patients. Tracking GI clones identified longitudinally at endoscopy in the blood also revealed an increased clonal expansion in patients with steroid-refractory disease. Immune repertoire sequencing-based methods could enable a novel personalized way to guide diagnosis and therapy in diseases where T-cell activity is a major determinant.

Stem cells in clinical practice: applications and warnings

Stem cells are a relevant source of information about cellular differentiation, molecular processes and tissue homeostasis, but also one of the most putative biological tools to treat degenerative diseases. This review focuses on human stem cells clinical and experimental applications. Our aim is to take a correct view of the available stem cell subtypes and their rational use in the medical area, with a specific focus on their therapeutic benefits and side effects. We have reviewed the main clinical trials dividing them basing on their clinical applications, and taking into account the ethical issue associated with the stem cell therapy.

Alloimmune response results in expansion of autoreactive donor CD4+ T cells in transplants that can mediate chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is considered an autoimmune-like disease mediated by donor CD4(+) T cells, but the origin of the autoreactive T cells is still controversial. In this article, we report that the transplantation of DBA/2 donor spleen cells into thymectomized MHC-matched allogeneic BALB/c recipients induced autoimmune-like cGVHD, although not in control syngeneic DBA/2 recipients. The donor-type CD4(+) T cells from the former but not the latter recipients induced autoimmune-like manifestations in secondary allogeneic BALB/c as well as syngeneic DBA/2 recipients. Transfer of donor-type CD4(+) T cells from secondary DBA/2 recipients with disease into syngeneic donor-type or allogeneic host-type tertiary recipients propagated autoimmune-like manifestations in both. Furthermore, TCR spectratyping revealed that the clonal expansion of the autoreactive CD4(+) T cells in cGVHD recipients was initiated by an alloimmune response. Finally, hybridoma CD4(+) T clones derived from DBA/2 recipients with disease proliferated similarly in response to stimulation by syngeneic donor-type or allogeneic host-type dendritic cells. These results demonstrate that the autoimmune-like manifestations in cGVHD can be mediated by a population of donor CD4(+) T cells in transplants that simultaneously recognize Ags presented by both donor and host APCs.

Treatment with GM-CSF secreting myeloid leukemia cell vaccine prior to autologous-BMT improves the survival of leukemia-challenged mice

Vaccination with irradiated autologous tumor cells, engineered to secrete granulocyte macrophage-colony stimulating factor (GM-CSF) (GM tumor), can generate potent antitumor effects when combined with autologous bone marrow transplantation (BMT). That notwithstanding, the post-BMT milieu, characterized by marked cytopenia, can pose a challenge to the implementation of vaccine immunotherapies. To bypass this problem, partial post-BMT immune reconstitution has been allowed to develop prior to vaccination. However, delaying vaccination can also potentially allow the expansion of residual tumor cells. Other approaches have used reinfusion of "primed" autologous lymphocytes and multiple administrations of GM tumor cells, which required the processing of large amounts of tumor. Utilizing the MMB3.19 murine myeloid leukemia model, we tested whether a single dose of GM tumor cells, 7 days prior to syngeneic BMT, could be a curative treatment in MMB3.19-challenged recipient mice. This vaccination protocol significantly improved survival of mice by eliciting long-lasting host immune responses that survived lethal irradiation, and were even protective against post-BMT tumor rechallenge. Furthermore, we demonstrated that mature donor lymphocytes can also play a limited role in mounting the antitumor response, but our pre-BMT vaccination strategy obviated the need for either established de novo immune reconstitution or the use of multiple post-BMT immunizations.

Pathogenesis and management of graft-versus-host disease

Allogeneic hematopoietic cell transplantation (HCT) is an important therapeutic option for various malignant and nonmalignant conditions. As allogeneic HCT continues to increase, greater attention is given to improvements in supportive care, infectious prophylaxis, immunosuppressive medications, and DNA-based tissue typing. However, graft versus host disease (GVHD) remains the most frequent and serious complication following allogeneic HCT and limits the broader application of this important therapy. Recent advances in the understanding of the pathogenesis of GVHD have led to new approaches to its management, including using it to preserve the graft versus leukemia effect following allogeneic transplant. This article reviews the important elements in the complex immunologic interactions involving cytokine networks, chemokine gradients, and the direct mediators of cellular cytotoxicity that cause clinical GVHD, and discusses the risk factors and strategies for management of GVHD.

Interleukin-7 permits Th1/Tc1 maturation and promotes ex vivo expansion of cord blood T cells: a critical step toward adoptive immunotherapy after cord blood transplantation

Donor leukocyte infusions (DLI) in the allogeneic hematopoietic transplant setting can provide a clinically relevant boost of immunity to reduce opportunistic infections and to increase graft-versus-leukemia activity. Despite significant advances in applicability, DLI has not been available for single-unit recipients of unrelated cord blood transplant. Ex vivo expansion of cord blood T cells can be achieved with interleukin (IL)-2 and CD3/CD28 costimulatory beads. However, significant apoptosis occurs in proliferating T cells, diminishing the yield and skewing the CD4/CD8 ratio in the T-cell population, jeopardizing the potential efficacy of DLI. In this study, we show that interleukin (IL)-7 not only reduces apoptosis of activated T lymphocytes and enhances their proliferation but also promotes functional maturation, leading to secretion of IFN-gamma and other key cytokines. Recognizing that infused T lymphocytes will need to meet microbial antigens in secondary lymphoid organs to generate effectors, we also show that expansion with IL-7 promotes the preservation of a polyclonal broad T-cell receptor repertoire and a surface phenotype that favors lymph node homing. Expanded lymphocytes lack alloreactivity against recipient and other allogeneic cells, indicating a favorable safety profile from graft-versus-host disease. Nevertheless, expanded T cells can be primed subsequently against lymphoid and myeloid leukemia cells to generate tumor-specific cytotoxic T cells. Taken together, our findings offer a major step in fulfilling critical numerical and biological requirements to quickly generate a DLI product ex vivo using a negligible fraction of a cord blood graft that provides a flexible adoptive immunotherapy platform for both children and adults.

Gas6 deficiency in recipient mice of allogeneic transplantation alleviates hepatic graft-versus-host disease

Growth arrest-specific gene 6 (Gas6) is expressed in antigen-presenting cells and endothelial cells (ECs) but not in T cells. When wild-type (WT) or Gas6(-/-) mice received allogeneic non-T cell-depleted bone marrow cells, hepatic graft-versus-host disease (GVHD) was alleviated in Gas6(-/-) recipients regardless of donor genotype, but not in WT recipients. T-cell infiltration was more prominent and diffuse in WT than in Gas6(-/-) recipients' liver. When mice received 0.5 x 10(6) allogeneic T cells with T cell-depleted allogeneic bone marrow, clinical signs indicated that GVHD was less severe in Gas6(-/-) than in WT recipients, as shown by a significant improvement of the survival and reduced liver GVHD. These data demonstrate that donor cells were not involved in the protection mechanism. In addition, lack of Gas6 in antigen-presenting cells did not affect WT or Gas6(-/-) T-cell proliferation. We therefore assessed the response of WT or Gas6(-/-) ECs to tumor necrosis factor-alpha. Lymphocyte transmigration was less extensive through Gas6(-/-) than WT ECs and was not accompanied by increases in adhesion molecule levels. Thus, the lack of Gas6 in ECs impaired donor T-cell transmigration into the liver, providing a rationale for considering Gas6 pathway as a potential nonimmunosuppressive target to minimize GVHD in patients receiving allogeneic hematopoietic stem cell transplantation.

Donor and recipient chemokine receptor CCR5 genotype is associated with survival after bone marrow transplantation

Despite continual improvement, morbidity and mortality after hematopoietic stem cell transplantation (HSCT) remain high. The importance of chemokines in HSCT lies in their regulation of immune responses that determine transplantation outcomes. We investigated the role of recipient and donor chemokine system gene polymorphisms by using a candidate gene approach on the incidence of graft-versus-host disease and posttransplantation outcomes in 1370 extensively human leukocyte antigen-matched, unrelated donor-recipient pairs by using multivariate Cox regression models. Our analysis identified that recipients homozygous for a common CCR5 haplotype (H1/H1) had better disease-free survival (DFS; P = .005) and overall survival (P = .021). When the same genotype of both the donor and recipient were considered in the models, a highly significant association with DFS and overall survival was noted (P < .001 and P = .007, respectively) with absolute differences in survival of up to 20% seen between the groups at 3 years after transplantation (50% DFS for pairs with recipient CCR5 H1/H1 vs 30% for pairs with donor CCR5 H1/H1). This finding suggests that donor and/or recipient CCR5 genotypes may be associated with HSCT outcome and suggests new diagnostic and therapeutic strategies for optimizing therapy.