T helper17 cells are sufficient but not necessary to induce acute graft-versus-host disease

Current Advances in Graft-versus-host Disease After Intestinal Transplantation

Graft-versus-host disease (GvHD) remains a potentially fatal complication following intestinal transplant (ITx). Over the past decade, advances in the understanding of the pathophysiology of this complex immunological phenomenon have led to the reassessment of the host systemic immune response and have created a gateway for novel preventive and therapeutic strategies. Although sufficient evidence dictates the use of corticosteroids as a first-line option, the treatment for refractory disease remains contentious and lacks a standardized therapeutic approach. Timely diagnosis remains crucial, and the advent of chimerism detection and immunological biomarkers have transformed the identification, prognostication, and potential for survival after GvHD in ITx. The objectives of the following review aim to discuss the clinical and diagnostic features, pathophysiology, advances in immune biomarkers, as well as therapeutic opportunities in the prevention and treatment of GvHD in ITx.

Interferon regulatory factor 4 plays a pivotal role in the development of aGVHD-associated colitis

Interferon regulatory factor 4 (IRF4) is a master transcription factor that regulates T helper cell (Th) differentiation. It interacts with the Basic leucine zipper transcription factor, ATF-like (BATF), depletion of which in CD4+ T cells abrogates acute graft-versus-host disease (aGVHD)-induced colitis. Here, we investigated the immune-regulatory role of Irf4 in a mouse model of MHC-mismatched bone marrow transplantation. We found that recipients of allogenic Irf4-/- CD4+ T cells developed less GVHD-related symptoms. Transcriptome analysis of re-isolated donor Irf4-/- CD4+ T helper (Th) cells, revealed gene expression profiles consistent with loss of effector T helper cell signatures and enrichment of a regulatory T cell (Treg) gene expression signature. In line with these findings, we observed a high expression of the transcription factor BTB and CNC homolog 2; (BACH2) in Irf4-/- T cells, which is associated with the formation of Treg cells and suppression of Th subset differentiation. We also found an association between BACH2 expression and Treg differentiation in patients with intestinal GVHD. Finally, our results indicate that IRF4 and BACH2 act as counterparts in Th cell polarization and immune homeostasis during GVHD. In conclusion, targeting the BACH2/IRF4-axis could help to develop novel therapeutic approaches against GVHD.

Influence of Housing Temperature and Genetic Diversity on Allogeneic T Cell-Induced Tissue Damage in Mice

The objective of this study was to determine how housing temperature and genetic diversity affect the onset and severity of allogeneic T cell-induced tissue damage in mice subjected to reduced intensity conditioning (RIC). We found that adoptive transfer of allogeneic CD4+ T cells from inbred donors into sub-lethally irradiated inbred recipients (I→I) housed at standard housing temperatures (ST; 22-24 °C) induced extensive BM and spleen damage in the absence of injury to any other tissue. Although engraftment of T cells in RIC-treated mice housed at their thermo-neutral temperature (TNT; 30-32 °C) also developed similar BM and spleen damage, their survival was markedly and significantly increased when compared to their ST counterparts. In contrast, the adoptive transfer of allogeneic T cells into RIC-treated outbred CD1 recipients failed to induce disease in any tissue at ST or TNT. The lack of tissue damage was not due to defects in donor T cell trafficking to BM or spleen but was associated with the presence of large numbers of B cells and myeloid cells within these tissues that are known to contain immunosuppressive regulatory B cells and myeloid-derived suppressor cells. These data demonstrate, for the first time, that housing temperature affects the survival of RIC-treated I→I mice and that RIC-conditioned outbred mice are resistant to allogeneic T cell-induced BM and spleen damage.

Murine models of graft versus host disease (GVHD): Focus on ocular GVHD

Graft versus host disease (GVHD) remains a major and serious complication of allogeneic hematopoietic stem cell transplantation. Based on the time of onset, clinical phenotypes, progression kinetics, and pathophysiology, GVHD is stratified into acute, chronic, and overlapping types. The eyes are among the most commonly affected organs in GVHD. Mouse models have played an important role in understanding the several key elements of GVHD pathobiology. The current review discusses the immunology, pathology, and key phenotypic features of mouse models of systemic GVHD. Furthermore, a critical appraisal of mouse models of ocular GVHD (oGVHD) is provided. The disease mechanisms underlying the ocular surface, meibomian gland, and lacrimal gland injury in these models are reviewed, and the relevance of oGVHD murine models to clinical oGVHD is also included.

Dissecting the regulatory network of transcription factors in T cell phenotype/functioning during GVHD and GVT

Transcription factors play a major role in regulation and orchestration of immune responses. The immunological context of the response can alter the regulatory networks required for proper functioning. While these networks have been well-studied in canonical immune contexts like infection, the transcription factor landscape during alloactivation remains unclear. This review addresses how transcription factors contribute to the functioning of mature alloactivated T cells. This review will also examine how these factors form a regulatory network to control alloresponses, with a focus specifically on those factors expressed by and controlling activity of T cells of the various subsets involved in graft-versus-host disease (GVHD) and graft-versus-tumor (GVT) responses.

International society for cell & gene therapy stem cell engineering committee: Cellular therapies for the treatment of graft-versus-host-disease after hematopoietic stem cell transplant

BACKGROUND AIMS

Allogeneic hematopoietic stem cell transplant is a curative approach for many malignant and non-malignant hematologic conditions. Despite advances in its prevention and treatment, the morbidity and mortality related to graft-versus-host disease (GVHD) remains. The mechanisms by which currently used pharmacologic agents impair the activation and proliferation of potentially alloreactive T cells reveal pathways essential for the detrimental activities of these cell populations. Importantly, these same pathways can be important in mediating the graft-versus-leukemia effect in recipients transplanted for malignant disease. This knowledge informs potential roles for cellular therapies such as mesenchymal stromal cells and regulatory T cells in preventing or treating GVHD. This article reviews the current state of adoptive cellular therapies focused on GVHD treatment.

METHODS

We conducted a search for scientific literature in PubMed® and ongoing clinical trials in clinicaltrial.gov with the keywords "Graft-versus-Host Disease (GVHD)," "Cellular Therapies," "Regulatory T cells (Tregs)," "Mesenchymal Stromal (Stem) Cells (MSCs)," "Natural Killer (NK) Cells," "Myeloid-derived suppressor cells (MDSCs)," and "Regulatory B-Cells (B-regs)." All the published and available clinical studies were included.

RESULTS

Although most of the existing clinical data focus on cellular therapies for GVHD prevention, there are observational and interventional clinical studies that explore the potential for cellular therapies to be safe modalities for GVHD treatment while maintaining the graft-versus-leukemia effect in the context of malignant diseases. However, there are multiple challenges that limit the broader use of these approaches in the clinical scenario.

CONCLUSIONS

There are many ongoing clinical trials to date with the promise to expand our actual knowledge on the role of cellular therapies for GVHD treatment in an attempt to improve GVHD-related outcomes in the near future.

Partially replacing cyclophosphamide with bendamustine in combination with cyclosporine A improves survival and reduces xenogeneic graft-versus-host-disease

Introduction

The use of allogeneic hematopoietic cell transplantation (allo-HCT) for treating hematological disorders is increasing, but the development of graft-versus-host disease (GvHD) remains a major cause of morbidity and mortality. The use of post-transplant cyclophosphamide (CY) has significantly improved outcomes following allo-HCT, but complications of viral reactivation due to delayed immune reconstitution or relapse remain. Other laboratories are evaluating the potential benefit of lowering the dose of CY given post-transplant, whereas our laboratory has been focusing on whether partially replacing CY with another DNA alkylating agent, bendamustine (BEN) may be advantageous in improving outcomes with allo-HCT.

Methods

Here, we utilized a xenogeneic GvHD (xGvHD) model in which immunodeficient NSG mice are infused with human peripheral blood mononuclear cells (PBMCs).

Results

We show that a lower dose of CY (25 mg/kg) given on days +3 and +4 or CY (75 mg/kg) given on only day +3 post-PBMC infusion is not sufficient for improving survival from xGvHD, but can be improved with the addition of BEN (15 mg/kg) on day +4 to day +3 CY (75 mg/kg). CY/BEN treated mice when combined with cyclosporine A (CSA) (10mg/kg daily from days +5 to +18 and thrice weekly thereafter), had improved outcomes over CY/CY +CSA treated mice. Infiltration of GvHD target organs was reduced in both CY/CY and CY/BEN treatment groups versus those receiving no treatment. CY/CY +CSA mice exhibited more severe xGvHD at day 10, marked by decreased serum albumin and increased intestinal permeability. CY/BEN treated mice had reductions in naïve, effector memory and Th17 polarized T cells. RNAseq analysis of splenocytes isolated from CY/CY and CY/BEN treated animals revealed increased gene set enrichment in multiple KEGG pathways related to cell migration, proliferation/differentiation, and inflammatory pathways, among others with CY/BEN treatment.

Conclusion

Together, we illustrate that the use of CY/BEN is safe and shows similar control of xGvHD to CY/CY, but when combined with CSA, survival with CY/BEN is significantly prolonged compared to CY/CY.

T Helper Cell Lineage-Defining Transcription Factors: Potent Targets for Specific GVHD Therapy?

Allogenic hematopoietic stem cell transplantation (allo-HSCT) represents a potent and potentially curative treatment for many hematopoietic malignancies and hematologic disorders in adults and children. The donor-derived immunity, elicited by the stem cell transplant, can prevent disease relapse but is also responsible for the induction of graft-versus-host disease (GVHD). The pathophysiology of acute GVHD is not completely understood yet. In general, acute GVHD is driven by the inflammatory and cytotoxic effect of alloreactive donor T cells. Since several experimental approaches indicate that CD4 T cells play an important role in initiation and progression of acute GVHD, the contribution of the different CD4 T helper (Th) cell subtypes in the pathomechanism and regulation of the disease is a central point of current research. Th lineages derive from naïve CD4 T cell progenitors and lineage commitment is initiated by the surrounding cytokine milieu and subsequent changes in the transcription factor (TF) profile. Each T cell subtype has its own effector characteristics, immunologic function, and lineage specific cytokine profile, leading to the association with different immune responses and diseases. Acute GVHD is thought to be mainly driven by the Th1/Th17 axis, whereas Treg cells are attributed to attenuate GVHD effects. As the differentiation of each Th subset highly depends on the specific composition of activating and repressing TFs, these present a potent target to alter the Th cell landscape towards a GVHD-ameliorating direction, e.g. by inhibiting Th1 and Th17 differentiation. The finding, that targeting of Th1 and Th17 differentiation appears more effective for GVHD-prevention than a strategy to inhibit Th1 and Th17 cytokines supports this concept. In this review, we shed light on the current advances of potent TF inhibitors to alter Th cell differentiation and consecutively attenuate GVHD. We will focus especially on preclinical studies and outcomes of TF inhibition in murine GVHD models. Finally, we will point out the possible impact of a Th cell subset-specific immune modulation in context of GVHD.

T Cell Subsets in Graft Versus Host Disease and Graft Versus Tumor

Allogeneic hematopoietic cell transplantation (allo-HCT) is an essential therapeutic modality for patients with hematological malignancies and other blood disorders. Unfortunately, acute graft-versus-host disease (aGVHD) remains a major source of morbidity and mortality following allo-HCT, which limits its use in a broader spectrum of patients. Chronic graft-versus-host disease (cGVHD) also remains the most common long-term complication of allo-HCT, occurring in reportedly 30-70% of patients surviving more than 100 days. Chronic GVHD is also the leading cause of non-relapse mortality (NRM) occurring more than 2 years after HCT for malignant disease. Graft versus tumor (GVT) is a major component of the overall beneficial effects of allogeneic HCT in the treatment of hematological malignancies. Better understanding of GVHD pathogenesis is important to identify new therapeutic targets for GVHD prevention and therapy. Emerging data suggest opposing roles for different T cell subsets, e.g., IFN-γ producing CD4+ and CD8+ T cells (Th1 and Tc1), IL-4 producing T cells (Th2 and Tc2), IL-17 producing T cells (Th17 and Tc17), IL-9 producing T cells (Th9 and Tc9), IL-22 producing T cells (Th22), T follicular helper cells (Tfh), regulatory T-cells (Treg) and tissue resident memory T cells (Trm) in GVHD and GVT etiology. In this review, we first summarize the general description of the cytokine signals that promote the differentiation of T cell subsets and the roles of these T cell subsets in the pathogenesis of GVHD. Next, we extensively explore preclinical findings of T cell subsets in both GVHD/GVT animal models and humans. Finally, we address recent findings about the roles of T-cell subsets in clinical GVHD and current strategies to modulate T-cell differentiation for treating and preventing GVHD in patients. Further exploring and outlining the immune biology of T-cell differentiation in GVHD that will provide more therapeutic options for maintaining success of allo-HCT.

Post-transplant cyclophosphamide limits reactive donor T cells and delays the development of graft-versus-host disease in a humanized mouse model

Graft-versus-host disease (GVHD) is a major complication of allogeneic haematopoietic stem cell transplantation (allo-HSCT) that develops when donor T cells in the graft become reactive against the host. Post-transplant cyclophosphamide (PTCy) is increasingly used in mismatched allo-HSCT, but how PTCy impacts donor T cells and reduces GVHD is unclear. This study aimed to determine the effect of PTCy on reactive human donor T cells and GVHD development in a preclinical humanized mouse model. Immunodeficient NOD-scid-IL2Rγ^null mice were injected intraperitoneally (i.p.) with 20 × 10⁶ human peripheral blood mononuclear cells stained with carboxyfluorescein succinimidyl ester (CFSE) (day 0). Mice were subsequently injected (i.p.) with PTCy (33 mg kg^-1 ) (PTCy-mice) or saline (saline-mice) (days 3 and 4). Mice were assessed for T-cell depletion on day 6 and monitored for GVHD for up to 10 weeks. Flow cytometric analysis of livers at day 6 revealed lower proportions of reactive (CFSE^low ) human (h) CD3⁺ T cells in PTCy-mice compared with saline-mice. Over 10 weeks, PTCy-mice showed reduced weight loss and clinical GVHD, with prolonged survival and reduced histological liver GVHD compared with saline-mice. PTCy-mice also demonstrated increased splenic hCD4⁺ :hCD8⁺ T-cell ratios and reduced splenic Tregs (hCD4⁺  hCD25⁺  hCD127^lo ) compared with saline-mice. This study demonstrates that PTCy reduces GVHD in a preclinical humanized mouse model. This corresponded to depletion of reactive human donor T cells, but fewer human Tregs.

Anti-ICOS mAb Targets Pathogenic IL-17A-expressing Cells in Canine Model of Chronic GVHD

BACKGROUND

Chronic graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality in transplant patients. We have previously shown that 3 doses of an anti-inducible costimulator (ICOS) mAb transiently ameliorated symptoms and extended survival of dogs affected by chronic GVHD over that of control dogs. The purpose of this study was to specifically correlate changes in T-cell populations in the peripheral blood with anti-ICOS treatment and chronic GVHD progression and regression to reach a better understanding of the mechanism of the disease and prioritize future studies.

METHODS

Peripheral blood cells from canines transplanted with DLA-mismatched bone marrow and peripheral blood mononuclear cells to generate chronic GVHD were analyzed by flow cytometry using a panel of antibodies specific to helper and cytolytic T cells.

RESULTS

Chronic GVHD was specifically associated with an increase in CD4+ICOS+ cells, ICOS+ cells expressing IL-17A, and CD8+ cells generating granzyme B. Treatment with anti-ICOS mAb at onset of chronic GVHD symptoms specifically targeted IL-17A+-expressing cells, transiently relieved symptoms, and lengthened survival but was unable to reduce the percentage of CD8+ T-cells expressing granzyme B.

CONCLUSIONS

These studies suggested a role for both CD4+ and CD8+ T cells in pathogenesis of chronic GVHD in the canine model. We propose that future studies should focus on further extending survival by developing a treatment that would control both CD4+ and CD8+ T cells.

The role of microbiota in allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is commonly performed to treat a variety of benign and malignant hematological diseases. Acute graft-versus-host disease (GVHD) is a major life-threatening complication that often occurs following allo-HSCT. Recently, improvements in methods to characterize the microbiota have led to a greater appreciation for how frequently and profoundly an alteration in microbial composition, or dysbiosis, can occur in allo-HSCT recipients to better decipher the complex interplay between microbiota and allo-HSCT outcomes.

AREAS COVERED

This article reviews the current knowledge of the microbiota's impact on allo-HSCT outcomes, including effects of microbiota-derived metabolites, and crosstalk between commensals and the allogeneic immune response. This article also summarizes the effects of HSCT and transplant-related procedures on microbiota, and recent developments in interventional strategies.

EXPERT OPINION

A growing body of literature indicates that the composition of the intestinal microbiota can function as a predictive biomarker for the risk and severity of acute GVHD, as well as overall survival, in patients undergoing allo-HSCT. Mechanisms underpinning these associations, however, are not well understood, and clinical strategies that modulate the microbiome to improve outcomes have yet to be fully developed. There is an unmet need to determine mechanisms to improve the efficacy of allo-HSCT.

Human CD83-targeted chimeric antigen receptor T cells prevent and treat graft-versus-host disease

Graft-versus-host disease (GVHD) remains an important cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HCT). For decades, GVHD prophylaxis has included calcineurin inhibitors, despite their incomplete efficacy and impairment of graft-versus-leukemia (GVL). Distinct from pharmacologic immune suppression, we have developed what we believe is a novel, human CD83-targeted chimeric antigen receptor (CAR) T cell for GVHD prevention. CD83 is expressed on allo-activated conventional CD4+ T cells (Tconvs) and proinflammatory dendritic cells (DCs), which are both implicated in GVHD pathogenesis. Human CD83 CAR T cells eradicate pathogenic CD83+ target cells, substantially increase the ratio of regulatory T cells (Tregs) to allo-activated Tconvs, and provide durable prevention of xenogeneic GVHD. CD83 CAR T cells are also capable of treating xenogeneic GVHD. We show that human acute myeloid leukemia (AML) expresses CD83 and that myeloid leukemia cell lines are readily killed by CD83 CAR T cells. Human CD83 CAR T cells are a promising cell-based approach to preventing 2 critical complications of allo-HCT - GVHD and relapse. Thus, the use of human CD83 CAR T cells for GVHD prevention and treatment, as well as for targeting CD83+ AML, warrants clinical investigation.

IL-17A Contributes to Lung Fibrosis in a Model of Chronic Pulmonary Graft-versus-host Disease

BACKGROUND

Chronic pulmonary graft-versus-host disease (cpGVHD) after hematopoietic cell transplant (HCT) manifests as progressive airway and parenchymal lung fibrosis. On the basis of our prior data, mice that undergo allogeneic HCT with Tbet-knockout donors (AlloTbet) have increased lung Th17 cells and IL-17A and develop fibrosis resembling human cpGVHD. The role of IL-17A in posttransplant pulmonary fibrosis remains incompletely understood. We hypothesized that IL-17A is necessary for development of murine cpGVHD in this model.

METHODS

AlloTbet mice received weekly intraperitoneal anti-IL-17A or IgG (200 μg/mouse) starting 2 weeks post-HCT and were sacrificed after week 5. Histologic airway and parenchymal fibrosis were semiquantitatively graded in a blinded fashion. Lung cells and proteins were measured by flow cytometry, ELISA, and multicytokine assays.

RESULTS

Anti-IL-17A modestly decreased airway and parenchymal lung fibrosis, along with a striking reduction in pulmonary neutrophilia, IL-6, MIP-1α, MIP-1β, CXCL1, and CXCL5 in AlloTbet mice. Additionally, anti-IL-17A decreased CCL2, inflammatory monocytes and macrophages, and Th17 cells.

CONCLUSIONS

In the setting of murine AlloHCT with Tbet donors, IL-17A blockade decreases fibrotic features of cpGVHD. This may be mediated by the observed reduction in neutrophils or specific lung monocyte and macrophage populations or alternatively via a direct effect on fibroblasts. Collectively, our results further suggest that anti-IL-17A strategies could prove useful in preventing alloimmune-driven fibrotic lung diseases.

Metabolic reprogramming augments potency of human pSTAT3-inhibited iTregs to suppress alloreactivity

Immunosuppressive donor Tregs can prevent graft-versus-host disease (GVHD) or solid-organ allograft rejection. We previously demonstrated that inhibiting STAT3 phosphorylation (pSTAT3) augments FOXP3 expression, stabilizing induced Tregs (iTregs). Here we report that human pSTAT3-inhibited iTregs prevent human skin graft rejection and xenogeneic GVHD yet spare donor antileukemia immunity. pSTAT3-inhibited iTregs express increased levels of skin-homing cutaneous lymphocyte-associated antigen, immunosuppressive GARP and PD-1, and IL-9 that supports tolerizing mast cells. Further, pSTAT3-inhibited iTregs significantly reduced alloreactive conventional T cells, Th1, and Th17 cells implicated in GVHD and tissue rejection and impaired infiltration by pathogenic Th2 cells. Mechanistically, pSTAT3 inhibition of iTregs provoked a shift in metabolism from oxidative phosphorylation (OxPhos) to glycolysis and reduced electron transport chain activity. Strikingly, cotreatment with coenzyme Q10 restored OxPhos in pSTAT3-inhibited iTregs and augmented their suppressive potency. These findings support the rationale for clinically testing the safety and efficacy of metabolically tuned, human pSTAT3-inhibited iTregs to control alloreactive T cells.

Resolution of acute intestinal graft-versus-host disease

Allogeneic transplantation of hematopoietic stem cells (allo-HCT) represents an increasingly employed therapeutic approach to potentially cure patients suffering from life-threatening malignant and autoimmune disorders. Despite its lifesaving potential, immune-mediated allo-reactivity inherent to the allogeneic transplantation can be observed within up to 50% of all allo-HCT patients regularly resulting in the manifestation of acute and/or chronic graft-versus-host disease (GvHD). Mechanistically, especially donor T cells are assumed to chiefly drive inflammation that can occur in virtually all organs, with the skin, liver, and gut representing as the most frequently affected anatomic sites. Especially in the presence of intestinal manifestations of GvHD, the risk that the disease takes a life-threatening, potentially fatal course is significantly increased. In the light of a rapid gain of knowledge in respect to decode innate and adaptive immunity related mechanisms as, e.g., cytokine networks, intracellular signaling pathways or environmental triggers as, e.g., the intestinal microbiota and the development of novel therapeutic approaches, detailed insight into endogenous mechanisms seeking to counterbalance the proinflammatory machinery or to proactively foster signals promoting the resolution of allo-driven intestinal inflammation is emerging. Here, we seek to highlight the key aspects of those mechanisms involved in and contributing to the resolution of GvHD-associated intestinal inflammation. Concomitantly, we would like to briefly outline and discuss promising future experimental targets suitable to be therapeutically employed to directionally deflect the tissue response from a proinflammatory to an inflammation-resolving type of intestinal GvHD after allo-HCT.

Graft-versus-host disease, but not graft-versus-leukemia immunity, is mediated by GM-CSF-licensed myeloid cells

Allogeneic hematopoietic cell transplantation (allo-HCT) not only is an effective treatment for several hematologic malignancies but can also result in potentially life-threatening graft-versus-host disease (GvHD). GvHD is caused by T cells within the allograft attacking nonmalignant host tissues; however, these same T cells mediate the therapeutic graft-versus-leukemia (GvL) response. Thus, there is an urgent need to understand how to mechanistically uncouple GvL from GvHD. Using preclinical models of full and partial MHC-mismatched HCT, we here show that the granulocyte-macrophage colony-stimulating factor (GM-CSF) produced by allogeneic T cells distinguishes between the two processes. GM-CSF drives GvHD pathology by licensing donor-derived phagocytes to produce inflammatory mediators such as interleukin-1β and reactive oxygen species. In contrast, GM-CSF did not affect allogeneic T cells or their capacity to eliminate leukemic cells, retaining undiminished GvL responses. Last, tissue biopsies and peripheral blood mononuclear cells from patients with grade IV GvHD showed an elevation of GM-CSF-producing T cells, suggesting that GM-CSF neutralization has translational potential in allo-HCT.

In Vitro Th17-Polarized Human CD4+ T Cells Exacerbate Xenogeneic Graft-versus-Host Disease

Acute graft-versus-host disease (aGVHD) is a severe complication of allogeneic hematopoietic stem cell transplantation. The role of Th17 cells in its pathophysiology remains a matter of debate. In this study, we assessed whether enrichment of human peripheral blood mononuclear cells (PBMCs) with in vitro Th17-polarized CD4⁺ T cells would exacerbate xenogeneic GVHD (xGVHD) into NOD-scid IL-2Rγ null (NSG) mice. Naive human CD4⁺ T cells were stimulated under Th17-skewing conditions for 8 to 10 days and then coinjected in NSG mice with fresh PBMCs from the same donor. We observed that Th17-polarized cells engrafted and migrated toward xGVHD target organs. They also acquired a double-expressing IL-17A⁺IFNγ⁺ profile in vivo. Importantly, cotransfer of Th17-polarized cells (1 × 10⁶) with PBMCs (1 × 10⁶) exacerbated xGVHD compared with transplantation of PBMCs alone (2 × 10⁶). Furthermore, PBMC cotransfer with Th17-polarized cells was more potent for xGVHD induction than cotransfer with naive CD4⁺ T cells stimulated in nonpolarizing conditions (Th0 cells, 1 × 10⁶ + 1 × 10⁶ PBMCs) or with Th1-polarized cells (1 × 10⁶ + 1 × 10⁶ PBMCs). In summary, our results suggest that human Th17-polarized cells can cooperate with PBMCs and be pathogenic in the NSG xGVHD model.

Targeting Inflammatory T Helper Cells via Retinoic Acid-Related Orphan Receptor Gamma t Is Ineffective to Prevent Allo-Response-Driven Colitis

Intestinal graft-versus-host disease (GvHD) is a life-threatening, inflammatory donor T cell-mediated complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the light of the reported efficacy of interleukin-23 (IL-23)-blockade to mitigate syngeneic intestinal inflammation in inflammatory bowel disease patients, targeting IL-23 and thereby interleukin-17a (IL-17a) producing T helper (Th17) cells as the T cell subset assumed to be mostly regulated by IL-23, has emerged as a putatively general concept to harness immune-mediated mucosal inflammation irrespective of the underlying trigger. However, the role of Th17 cells during allo-response driven colitis remains ambiguous due to a series of studies with inconclusive results. Interestingly, we recently identified granulocyte-macrophage colony-stimulating factor (GM-CSF+) T cells to be promoted by interleukin-7 (IL-7) signaling and controlled by the activating protein-1 transcription factor family member basic leucine zipper transcription factor ATF-like (BATF) as critical mediators of intestinal GvHD in mice. Given the dual role of BATF, the contribution of IL-23-mediated signaling within donor T cells and bona fide Th17 cells remains to be delineated from the regulation of GM-CSF+ T cells in the absence of BATF. Here, we found in a complete MHC class I-mismatched model that genetic inactivation of the IL-23 receptor (IL-23R) or the transcription factor retinoic acid-related orphan receptor gamma t (RORγt) within donor T cells similarly ablated Th17 cell formation in vivo but preserved the T cells' ability to induce intestinal GvHD in a compared to wild-type controls indistinguishable manner. Importantly, RORγt-independent manifestation of intestinal GvHD was completely dependent on BATF-regulated GM-CSF+ T cells as BATF/RORγt double-deficient T cells failed to induce colitis and the antibody-mediated blockage of IL-7/IL-7R interaction and GM-CSF significantly diminished signs of intestinal GvHD elicited by RORγt-deficient donor T cells. Finally, in analogy to our murine studies, colonic RORC expression levels inversely correlated with the presence of GvHD in allo-HSCT patients. Together, this study provides a crucial example of a BATF-dependent, however, IL-23R signaling- and RORγt-, i.e., Th17 fate-independent regulation of a colitogenic T cell population critically impacting the current understanding of intestinal GvHD.

In vivo IL-12/IL-23p40 neutralization blocks Th1/Th17 response after allogeneic hematopoietic cell transplantation

T-helper 1 and T-helper 17 lymphocytes mediate acute graft-versus-host disease (GvHD). Interleukin 12 is critical for T-helper 1 differentiation and interleukin 23 for T-helper 17 maintenance. Interleukin 12 and 23 are heterodimeric cytokines that share the p40 subunit (IL-12/IL-23p40). In a randomized, blinded, placebo-controlled trial, we examined the biological impact and clinical outcomes following IL-12/IL-23p40 neutralization using ustekinumab. Thirty patients received peripheral blood mobilized hematopoietic cell transplantation (HCT) from HLA-matched sibling or unrelated donors, received sirolimus plus tacrolimus as GvHD prophylaxis, and were randomized to ustekinumab versus placebo with 1:1 allocation after stratification by donor type. The primary end point of the trial was the mean percentage (%) T-regulatory (Treg) cells on day 30 post HCT. Ustekinumab was delivered by subcutaneous injection on day -1 and day +20 after transplantation. On day 30 post transplant, no significant difference in % Treg was observed. Ustekinumab suppressed serum IL-12/IL-23p40 levels. Host-reactive donor alloresponse at days 30 and 90 after transplantation was polarized with significant reduction in IL-17 and IFN-α production and increase in IL-4. No toxicity attributed to ustekinumab was observed. Overall survival and National Institute of Health moderate/severe chronic GvHD-free, relapse-free survival were significantly improved among ustekinumab-treated patients. No significant improvements were observed in acute or chronic GvHD, relapse, or non-relapse mortality. These data provide first evidence that IL-12/IL-23p40 neutralization can polarize donor anti-host alloresponse in vivo and provide initial clinical efficacy evidence to be tested in subsequent trials. (Trial registered at clinicaltrials.gov identifier: 01713400).

BATF-dependent IL-7RhiGM-CSF+ T cells control intestinal graft-versus-host disease

Acute graft-versus-host disease (GVHD) represents a severe, T cell-driven inflammatory complication following allogeneic hematopoietic cell transplantation (allo-HCT). GVHD often affects the intestine and is associated with a poor prognosis. Although frequently detectable, proinflammatory mechanisms exerted by intestinal tissue-infiltrating Th cell subsets remain to be fully elucidated. Here, we show that the Th17-defining transcription factor basic leucine zipper transcription factor ATF-like (BATF) was strongly regulated across human and mouse intestinal GVHD tissues. Studies in complete MHC-mismatched and minor histocompatibility-mismatched (miHA-mismatched) GVHD models revealed that BATF-expressing T cells were functionally indispensable for intestinal GVHD manifestation. Mechanistically, BATF controlled the formation of colon-infiltrating, IL-7 receptor-positive (IL-7R+), granulocyte-macrophage colony-stimulating factor-positive (GM-CSF+), donor T effector memory (Tem) cells. This T cell subset was sufficient to promote intestinal GVHD, while its occurrence was largely dependent on T cell-intrinsic BATF expression, required IL-7-IL-7R interaction, and was enhanced by GM-CSF. Thus, this study identifies BATF-dependent pathogenic GM-CSF+ effector T cells as critical promoters of intestinal inflammation in GVHD and hence putatively provides mechanistic insight into inflammatory processes previously assumed to be selectively Th17 driven.

The Biology of Chronic Graft-versus-Host Disease: A Task Force Report from the National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease

Chronic graft-versus-host disease (GVHD) is the leading cause of late, nonrelapse mortality and disability in allogeneic hematopoietic cell transplantation recipients and a major obstacle to improving outcomes. The biology of chronic GVHD remains enigmatic, but understanding the underpinnings of the immunologic mechanisms responsible for the initiation and progression of disease is fundamental to developing effective prevention and treatment strategies. The goals of this task force review are as follows: This document is intended as a review of our understanding of chronic GVHD biology and therapies resulting from preclinical studies, and as a platform for developing innovative clinical strategies to prevent and treat chronic GVHD.

Adoptively transferred donor IL-17-producing CD4+ T cells augment, but IL-17 alleviates, acute graft-versus-host disease

The role of IL-17 and IL-17-producing CD4⁺ T cells in acute graft-versus-host disease (GVHD) has been controversial in recent mouse and human studies. We carried out studies in a murine acute GVHD model of fully major histocompatibility complex-mismatched myeloablative bone marrow transplantation. We showed that donor wild-type CD4⁺ T cells exacerbated acute GVHD compared with IL-17^-/- CD4⁺ T cells, while IL-17 reduced the severity of acute GVHD. The augmentation of acute GVHD by transferred donor IL-17-producing CD4⁺ T cells was associated with increased Th1 responses, while IL-17 decreased the percentages of Th1 cells in the GVHD target organs. Furthermore, IL-17 reduced the infiltration of macrophages into the GVHD tissues. In vitro study showed that IL-17 could downregulate Th1 responses, possibly through inhibiting IL-12 production by donor macrophages. Depletion of macrophages in vivo diminished the protective effect of IL-17. Our results demonstrated the differential roles of adoptively transferred donor IL-17-producing CD4⁺ T cells and IL-17 in the same acute GVHD model.

Systems analysis uncovers inflammatory Th/Tc17-driven modules during acute GVHD in monkey and human T cells

One of the central challenges of transplantation is the development of alloreactivity despite the use of multiagent immunoprophylaxis. Effective control of this immune suppression-resistant T-cell activation represents one of the key unmet needs in the fields of both solid-organ and hematopoietic stem cell transplant (HCT). To address this unmet need, we have used a highly translational nonhuman primate (NHP) model to interrogate the transcriptional signature of T cells during breakthrough acute graft-versus-host disease (GVHD) that occurs in the setting of clinically relevant immune suppression and compared this to the hyperacute GVHD, which develops in unprophylaxed or suboptimally prophylaxed transplant recipients. Our results demonstrate the complex character of the alloreactivity that develops during ongoing immunoprophylaxis and identify 3 key transcriptional hallmarks of breakthrough acute GVHD that are not observed in hyperacute GVHD: (1) T-cell persistence rather than proliferation, (2) evidence for highly inflammatory transcriptional programming, and (3) skewing toward a T helper (Th)/T cytotoxic (Tc)17 transcriptional program. Importantly, the gene coexpression profiles from human HCT recipients who developed GVHD while on immunosuppressive prophylactic agents recapitulated the patterns observed in NHP, and demonstrated an evolution toward a more inflammatory signature as time posttransplant progressed. These results strongly implicate the evolution of both inflammatory and interleukin 17-based immune pathogenesis in GVHD, and provide the first map of this evolving process in primates in the setting of clinically relevant immunomodulation. This map represents a novel transcriptomic resource for further systems-based efforts to study the breakthrough alloresponse that occurs posttransplant despite immunoprophylaxis and to develop evidence-based strategies for effective treatment of this disease.

The Role of Animal Models in the Study of Hematopoietic Stem Cell Transplantation and GvHD: A Historical Overview

Bone marrow transplantation (BMT) is the only therapeutic option for many hematological malignancies, but its applicability is limited by life-threatening complications, such as graft-versus-host disease (GvHD). The last decades have seen great advances in the understanding of BMT and its related complications; in particular GvHD. Animal models are beneficial to study complex diseases, as they allow dissecting the contribution of single components in the development of the disease. Most of the current knowledge on the therapeutic mechanisms of BMT derives from studies in animal models. Parallel to BMT, the understanding of the pathophysiology of GvHD, as well as the development of new treatment regimens, has also been supported by studies in animal models. Pre-clinical experimentation is the basis for deep understanding and successful improvements of clinical applications. In this review, we retrace the history of BMT and GvHD by describing how the studies in animal models have paved the way to the many advances in the field. We also describe how animal models contributed to the understanding of GvHD pathophysiology and how they are fundamental for the discovery of new treatments.

High expression of heme oxygenase-1 in target organs may attenuate acute graft-versus-host disease through regulation of immune balance of TH17/Treg

The high incidence of acute graft-versus-host disease (aGVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Grades III and IV aGVHD are the leading causes of death in allo-HSCT recipients. Heme oxygenase-1(HO-1) has anti-inflammatory and immune-regulatory functions. In this study, we evaluated the none GVHD and grade I-IV patients samples which were collected at the first re-examination after successful allo-HSCT, we found that expressions of HO-1 mRNA in the bone marrow and peripheral blood mononuclear cells of allo-HSCT recipients who had subsequent non-GVHD and grade I aGVHD were significantly higher than those in patients with Grade III-IV aGVHD. We then demonstrated that enhanced expression of HO-1 in target organs by infusing HO-1-gene-modified Mesenchymal stem cells (MSCs) alleviated the clinical and histopathological severity of aGVHD in experimental mice. Flow cytometry revealed a higher expression of Treg cells and a lower expression of TH17 cells in splenic and lymph node tissues of mice with enhanced HO-1 expression, as compared to that in the aGVHD mice. This was further substantiated by lower expression levels of ROR-Υt and IL-17A mRNA, and higher levels of Foxp3 mRNA in the splenic tissue of mice with enhanced HO-1 expression. Our results indicate that high expression of HO-1 may reduce the severity of aGVHD by regulation of the TH17/Treg balance.

Metabolic reprogramming of alloantigen-activated T cells after hematopoietic cell transplantation

Alloreactive donor T cells are the driving force in the induction of graft-versus-host disease (GVHD), yet little is known about T cell metabolism in response to alloantigens after hematopoietic cell transplantation (HCT). Here, we have demonstrated that donor T cells undergo metabolic reprograming after allogeneic HCT. Specifically, we employed a murine allogeneic BM transplant model and determined that T cells switch from fatty acid β-oxidation (FAO) and pyruvate oxidation via the tricarboxylic (TCA) cycle to aerobic glycolysis, thereby increasing dependence upon glutaminolysis and the pentose phosphate pathway. Glycolysis was required for optimal function of alloantigen-activated T cells and induction of GVHD, as inhibition of glycolysis by targeting mTORC1 or 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) ameliorated GVHD mortality and morbidity. Together, our results indicate that donor T cells use glycolysis as the predominant metabolic process after allogeneic HCT and suggest that glycolysis has potential as a therapeutic target for the control of GVHD.

Translational opportunities for targeting the Th17 axis in acute graft-vs.-host disease

Allogeneic stem cell transplantation (allo-SCT) is a curative therapy for different life-threatening malignant and non-malignant hematologic disorders. Acute graft-vs.-host disease (aGVHD) and particularly gastrointestinal aGVHD remains a major source of morbidity and mortality following allo-SCT, which limits the use of this treatment in a broader spectrum of patients. Better understanding of aGVHD pathophysiology is indispensable to identify new therapeutic targets for aGVHD prevention and therapy. Growing amount of data suggest a role for T helper (Th)17 cells in aGVHD pathophysiology. In this review, we will discuss the current knowledge in this area in animal models and in humans. We will then describe new potential treatments for aGVHD along the Th17 axis.

Antibodies from donor B cells perpetuate cutaneous chronic graft-versus-host disease in mice

Cutaneous sclerosis is one of the most common clinical manifestations of chronic graft-versus-host disease (cGVHD). Donor CD4(+) T and B cells play important roles in cGVHD pathogenesis, but the role of antibodies from donor B cells remains unclear. In the current studies, we generated immunoglobulin (Ig)H(µγ1) DBA/2 mice whose B cells have normal antigen-presentation and regulatory functions but cannot secrete antibodies. With a murine cGVHD model using DBA/2 donors and BALB/c recipients, we have shown that wild-type (WT) grafts induce persistent cGVHD with damage in the thymus, peripheral lymphoid organs, and skin, as well as cutaneous T helper 17 cell (Th17) infiltration. In contrast, IgH(µγ1) grafts induced only transient cGVHD with little damage in the thymus or peripheral lymph organs or with little cutaneous Th17 infiltration. Injections of IgG-containing sera from cGVHD recipients given WT grafts but not IgG-deficient sera from recipients given IgH(µγ1) grafts led to deposition of IgG in the thymus and skin, with resulting damage in the thymus and peripheral lymph organs, cutaneous Th17 infiltration, and perpetuation of cGVHD in recipients given IgH(µγ1) grafts. These results indicate that donor B-cell antibodies augment cutaneous cGVHD in part by damaging the thymus and increasing tissue infiltration of pathogenic Th17 cells.

Cellular and molecular mechanisms in graft-versus-host disease

Graft-versus-host disease is a complication in patients undergoing hematopoietic stem cell transplantation. Graft-versus-host disease includes acute graft-versus-host disease and chronic graft-versus-host disease. Host APCs (e.g., dendritic cells and macrophages), effector T cells (e.g., Th1, Th17, and abnormal Th17:regulatory T cell ratio), B cells, and NK cells are implicated in graft-versus-host disease physiopathology. Proinflammation cytokines (e.g., IL-17, IL-1β, and TNF-α) are increased in graft-versus-host disease . Costimulatory molecules play an important role in inducing graft-versus-host disease . Pattern-recognition receptors, such as TLRs and nucleotide-binding oligomerization domain-like receptors, are critically involved in the pathogenesis of graft-versus-host disease . Complement system C3 mediates Th1/Th17 polarization in human T cell activation and skin graft-versus-host disease. Accumulation of CD26 T cells in graft-versus-host disease target organs was found. As a therapeutic target, soluble CD83 molecules or antibodies have been demonstrated to have therapeutic effects against graft-versus-host disease, and signaling molecules promote the inflammatory and immune process of graft-versus-host disease . These immune cells and molecules could be the predictors of graft-versus-host disease development and the drug targets of the treatments for graft-versus-host disease. This article focuses on major advances on cellular and molecular mechanisms in graft-versus-host disease.

Essential Role of Interleukin-12/23p40 in the Development of Graft-versus-Host Disease in Mice

Graft-versus-host disease (GVHD), in both its acute (aGVHD) and chronic (cGVHD) forms, remains a major obstacle impeding successful allogeneic hematopoietic stem cell transplantation (allo-HSCT). T cells, in particular pathogenic T helper (Th) 1 and Th17 subsets, are a driving force for the induction of GVHD. IL-12 and IL-23 cytokines share a common p40 subunit and play a critical role in driving Th1 differentiation and in stabilizing the Th17 phenotype, respectively. In our current study, we hypothesized that p40 is an essential cytokine in the development of GVHD. By using p40-deficient mice, we found that both donor- and host-derived p40 contribute to the development of aGVHD. Neutralization of p40 with an anti-p40 mAb inhibited Th1- and Th17-polarization in vitro. Furthermore, anti-p40 treatment reduced aGVHD severity while preserving the graft-versus-leukemia (GVL) activity. Alleviation of aGVHD was associated with an increase of Th2 differentiation and a decrease of Th1 and Th17 effector T cells in the GVHD target organs. In addition, anti-p40 treatment attenuated the severity of sclerodermatous cGVHD. These results provide a strong rationale that blockade of p40 may represent a promising therapeutic strategy in preventing and treating aGVHD and cGVHD while sparing the GVL effect after allo-HSCT.

Inhibition of the interleukin-6 signaling pathway: a strategy to induce immune tolerance

Interleukin-6 (IL-6) is a proinflammatory cytokine that is multifunctional, with multifaceted effects. IL-6 signaling plays a vital role in the control of the differentiation and activation of T lymphocytes by inducing different pathways. In particular, IL-6 controls the balance between Th17 cells and regulatory T (Treg) cells. An imbalance between Treg and Th17 cells is thought to play a pathological role in various immune-mediated diseases. Deregulated IL-6 production and signaling are associated with immune tolerance. Therefore, methods of inhibiting IL-6 production, receptors, and signaling pathways are strategies that are currently being widely pursued to develop novel therapies that induce immune tolerance. This survey aims to provide an updated account of why IL-6 inhibitors are becoming a vital class of drugs that are potentially useful for inducing immune tolerance as a treatment for autoimmune diseases and transplant rejection. In addition, we discuss the effect of targeting IL-6 in recent experimental and clinical studies on autoimmune diseases and transplant rejection.

IL-35 mitigates murine acute graft-versus-host disease with retention of graft-versus-leukemia effects

IL-35 is a newly discovered inhibitory cytokine secreted by regulatory T cells (Tregs) and may have therapeutic potential in several inflammatory disorders. Acute graft-versus-host disease (aGVHD) is a major complication of allogeneic hematopoietic stem cell transplantation and caused by donor T cells and inflammatory cytokines. The role of IL-35 in aGVHD is still unknown. Here we demonstrate that IL-35 overexpression suppresses CD4(+) effector T-cell activation, leading to a reduction in alloreactive T-cell responses and aGVHD severity. It also leads to the expansion of CD4(+)Foxp3(+) Tregs in the aGVHD target organs. Furthermore, IL-35 overexpression results in a selective decrease in the frequency of Th1 cells and an increase of IL-10-producing CD4(+) T cells in aGVHD target tissues. Serum levels of TNF-α, IFN-γ, IL-6, IL-22 and IL-23 decrease and IL-10 increases in response to IL-35. Most importantly, IL-35 preserves graft-versus-leukemia effect. Finally, aGVHD grade 2-4 patients have decreased serum IL-35 levels comparing with time-matched patients with aGVHD grade 0-1. Our findings indicate that IL-35 has an important role in reducing aGVHD through promoting the expansion of Tregs and repressing Th1 responses, and should be investigated as the therapeutic strategy for aGVHD.

CD4+ T cell STAT3 phosphorylation precedes acute GVHD, and subsequent Th17 tissue invasion correlates with GVHD severity and therapeutic response

Th17 cells contribute to severe GVHD in murine bone marrow transplantation. Targeted deletion of the RORγt transcription factor or blockade of the JAK2-STAT3 axis suppresses IL-17 production and alloreactivity by Th17 cells. Here, we show that pSTAT3 Y705 is increased significantly in CD4(+) T cells among human recipients of allogeneic HCT before the onset of Grade II-IV acute GVHD. Examination of target-organ tissues at the time of GVHD diagnosis indicates that the amount of RORγt + Th17 cells is significantly higher in severe GVHD. Greater accumulation of tissue-resident Th17 cells also correlates with the use of MTX- compared with Rapa-based GVHD prophylaxis, as well as a poor therapeutic response to glucocorticoids. RORγt is optimally suppressed by concurrent neutralization of TORC1 with Rapa and inhibition of STAT3 activation with S3I-201, supporting that mTOR- and STAT3-dependent pathways converge upon RORγt gene expression. Rapa-resistant T cell proliferation can be totally inhibited by STAT3 blockade during initial allosensitization. We conclude that STAT3 signaling and resultant Th17 tissue accumulation are closely associated with acute GVHD onset, severity, and treatment outcome. Future studies are needed to validate the association of STAT3 activity in acute GVHD. Novel GVHD prevention strategies that incorporate dual STAT3 and mTOR inhibition merit investigation.

T-bet is critical for the development of acute graft-versus-host disease through controlling T cell differentiation and function

T-bet is a master regulator for IFN-γ production and Th1 differentiation. We evaluated the roles of T-bet and IFN-γ in T cell responses in acute graft-versus-host disease (GVHD) and found that T-bet(-/-) T cells induced significantly less GVHD compared with wild-type or IFN-γ(-/-) counterparts in both MHC-mismatched and MHC-matched but minor histocompatibility Ag-mismatched models driven by CD4 T cells. T-bet(-/-), but not IFN-γ(-/-), CD4 T cells had a markedly reduced ability to cause tissue damage in liver and gut. This distinct outcome is reflected by the differential gene expression on donor CD4 T cells deficient for T-bet or IFN-γ. At mRNA and protein levels, we defined several T-bet-dependent molecules that may account for the impaired ability of T-bet(-/-) T cells to migrate into target organs and to produce Th1-related cytokines. Moreover, these molecules were independent of either endogenous IFN-γ, such as CXCR3 and programmed death-1, or systematic IFN-γ, such as NKG2D, I-A(b), and granzyme B. Although both T-bet(-/-) and IFN-γ(-/-) CD4 T cells are prone to differentiate into Th17 cells, polarized Th17 cells deficient for T-bet but not for IFN-γ had a significantly reduced ability to cause GVHD. Finally, T-bet(-/-) T cells had a compromised graft-versus-leukemia effect, which could be essentially reversed by neutralization of IL-17 in the recipients. We conclude that T-bet is required for Th1 differentiation and migration, as well as for optimal function of Th17 cells. Thus, targeting T-bet or regulating its downstream effectors independent of IFN-γ may be a promising strategy to control GVHD in the clinic.

IL-17 genetic and immunophenotypic evaluation in chronic graft-versus-host disease

Although interleukin-17 (IL-17) is a recently discovered cytokine associated with several autoimmune diseases, its role in the pathogenesis of chronic graft-versus-host disease (cGVHD) was not established yet. The objective of this study was to investigate the association of IL17A and IL17F genes polymorphisms and IL-17A and IL-17F levels with cGVHD. IL-17A expression was also investigated in CD4(+) T cells of patients with systemic cGVHD. For Part I of the study, fifty-eight allo-HSCT recipients and donors were prospectively studied. Blood samples were obtained to determine IL17A and IL17F genes polymorphisms. Cytokines levels in blood and saliva were assessed by ELISA at days +35 and +100 after HSCT. In Part II, for the immunophenotypic evaluation, eight patients with systemic cGVHD were selected and the expression of IL-17A was evaluated. We found association between recipient AA genotype with systemic cGVHD. No association was observed between IL-17A levels and cGVHD. Lower IL-17A levels in the blood were associated with AA genotype. In flow cytometry analysis, decreased expression of IL-17A was observed in patients with cGVHD after stimulation. In conclusion, IL-17A may have an important role in the development of systemic cGVHD.

Association of IL-17 gene polymorphisms and serum level with graft versus host disease after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Cytokines are important factors determining the outcome of transplantation. Host ability in cytokine production may be affected by cytokine genes polymorphisms. The aim of the present study was to investigate the effect of IL-17 gene polymorphisms on outcome of Hematopoietic stem cell transplantation.

MATERIALS AND METHODS

A total of 60 bone marrow recipients were included in this study. Twenty-five recipients (41.66%) underwent a GVHD. IL-17 gene polymorphisms were evaluated by PCR-RFLP method and the serum levels were also checked by ELISA.

RESULTS

No significant differences in distribution of the IL-17(A/G) (rs3819025) genotypes and alleles were observed between two groups. But, IL-17 (A/G, -197) GG genotype was found to be significantly higher in GVHD group compared to those of non-GVHD group (P = 0.04). Interestingly, after stratification of patients according severity of GVHD, IL-17 (rs3819025) G allele was remained significantly higher in GVHD grade (0-I) group compared to those of grade (II-IV) group (P = 0.05). In addition, after categorization of patients according to their sex, IL-17-197 GG genotype showed a significant association with non-GVHD in male patients (P = 0.05). IL-17 serum levels did not show any significant difference between GVHD and non GVHD groups.

CONCLUSION

Results indicated that IL-17197 GG genotype, G allele of (rs3819025) and its serum level have predictive values for severity of GVHD. Also, IL-17-197 GG genotype is a sex dependent genetic risk factor for development of GVHD, but this subject need to be studied in different population.

Kinetics of IFN-γ and IL-17 Production by CD4 and CD8 T Cells during Acute Graft-versus-Host Disease

Graft-versus-host disease (GVHD) is a fatal complication that occurs after allogeneic hematopoietic stem cell transplantation. To understand the dynamics of CD4 and CD8 T cell production of IFN-γ and IL-17 during GVHD progression, we established a GVHD model by transplanting T cell-depleted bone marrow (TCD-BM) and purified T cells from B6 mice into irradiated BALB.B, creating an MHC-matched but minor histocompatibility (H) antigen-mismatched transplantation (B6 → BALB.B GVHD). Transplantation-induced GVHD was confirmed by the presence of the appropriate compositional changes in the T cell compartments and innate immune cells in the blood and the systemic secretion of inflammatory cytokines. Using this B6 → BALB.B GVHD model, we showed that the production of IFN-γ and IL-17 by CD4 T cells preceded that by CD8 T cells in the spleen, mesenteric lymph node, liver, and lung in the BALB.B GVHD host, and Th1 differentiation predated Th17 differentiation in all organs during GVHD progression. Such changes in cytokine production were based on changes in cytokine gene expression by the T cells at different time points during GVHD development. These results demonstrate that both IFN-γ and IL-17 are produced by CD4 and CD8 T cells but with different kinetics during GVHD progression.

Helper T-cell differentiation in graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective therapeutic option for many malignant diseases. However, the efficacy of allo-HSCT is limited by the occurrence of destructive graft-versus-host disease (GVHD). Since allogeneic T cells are the driving force in the development of GVHD, their activation, proliferation, and differentiation are key factors to understanding GVHD pathogenesis. This review focuses on one critical aspect: the differentiation and function of helper T (Th) cells in acute GVHD. We first summarize well-established subsets including Th1, Th2, Th17, and T-regulatory cells; their flexibility, plasticity, and epigenetic modification; and newly identified subsets including Th9, Th22, and T follicular helper cells. Next, we extensively discuss preclinical findings of Th-cell lineages in GVHD: the networks of transcription factors involved in differentiation, the cytokine and signaling requirements for development, the reciprocal differentiation features, and the regulation of microRNAs on T-cell differentiation. Finally, we briefly summarize the recent findings on the roles of T-cell subsets in clinical GVHD and ongoing strategies to modify T-cell differentiation for controlling GVHD in patients. We believe further exploration and understanding of the immunobiology of T-cell differentiation in GVHD will expand therapeutic options for the continuing success of allo-HSCT.

Current data on IL-17 and Th17 cells and implications for graft versus host disease

Human interleukin 17 was first described in 1995 as a new cytokine produced primarily by activated T CD4+ cells that stimulate the secretion of IL-6 and IL-8 by human fibroblasts, besides increasing the expression of ICAM-1. Various authors have reported that IL-17A has a role in the protection of organisms against extracellular bacteria and fungi due to the capacity of IL-17A to recruit neutrophils to the areas of infection, evidencing a pathological role in various models of autoimmune diseases, such as experimental autoimmune encephalitis and arthritis. The participation of IL-17A has also been described in the acute rejection of organ transplants and graft versus host disease. However, the greatest revolution in research with IL-17 happened in 2000, when it was proposed that IL-17 cannot be classified as Th1 or Th2, but rather, simply as a new lineage of IL-17-producing T-cells. These findings modified the previously established Th1/Th2 paradigm, leading to the definition of the CD3+ CD4+ Th17 cellular subtype and establishment of a new model to explain the origin of various immune events, as well as its implication in the graft versus host disease that is discussed in depth in this article.

c-Rel is an essential transcription factor for the development of acute graft-versus-host disease in mice

Transcription factors of the Rel/NF-κB family are known to play different roles in immunity and inflammation, although the putative role of c-Rel in transplant tolerance and graft-versus-host disease (GVHD) remains elusive. We report here that T cells deficient for c-Rel have a dramatically reduced ability to cause acute GVHD after allogeneic bone marrow transplantation using major and minor histocompatibility mismatched murine models. In the study to understand the underlying mechanisms, we found that c-Rel(-/-) T cells had a reduced ability to expand in lymphoid organs and to infiltrate in GVHD target organs in allogeneic recipients. c-Rel(-/-) T cells were defective in the differentiation into Th1 cells after encountering alloantigens, but were enhanced in the differentiation toward Foxp3(+) regulatory T (Treg) cells. Furthermore, c-Rel(-/-) T cells had largely preserved activity to mediate graft-versus-leukemia response. Taken together, our findings indicate that c-Rel plays an essential role in T cells in the induction of acute GVHD, and suggest that c-Rel can be a potential target for therapeutic intervention in allogeneic hematopoietic cell transplantation in the clinic.

The expression of Th17-associated cytokines in human acute graft-versus-host disease

The role of Th17 cells and Th17-associated cytokines in the development of acute graft-versus-host disease (aGVHD) in clinical allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients is not well established. In the current study, a cohort of 69 allo-HSCT patients was examined for the percentages of Th17 and FoxP3(+) Treg cells and the expressions of RORγt and FoxP3 in peripheral blood mononuclear cells (PBMCs). The Th17 percentage and RORγt expression were significantly higher, whereas Treg percentage and FoxP3 expression were significantly lower in severe aGVHD (grade 3 to 4) and mild aGVHD (grade 1 to 2) patients than in patients without aGVHD (grade 0) and healthy donors. We then investigated the expressions of Th17-associated cytokines, including TGF-β, IL-6, IL-1β, IL-17, IL-21, IL-22, IL-23, as well as IL-23R in the PBMCs of patients after allo-HSCT. The expressions of IL-17 and IL-22 in CD4(+) T cells were also examined. The results showed that the expressions of IL-6, IL-1β, IL-17, IL-21, IL-23, and IL-23R were all increased, whereas IL-22 expression was decreased in aGVHD patients. The changes were also correlated with the severity of aGVHD. We also investigated the dynamic changes of Th17/Treg cells and Th17-associated cytokines in patients during the onset and resolution of aGVHD. The results demonstrated a reciprocal relationship between Treg and Th17 cells. Th17-associated cytokine expressions, namely IL-17 and IL-23, were closely related to the occurrence and resolution of aGVHD. We conclude that the dynamic balance between the Th17 and FoxP3(+) Treg cells and the changes of Th17-associated cytokines could be the indicators of the disease progression and promising candidates of prognostic biomarkers of aGVHD.

PLZF confers effector functions to donor T cells that preserve graft-versus-tumor effects while attenuating GVHD

Efforts to limit GVHD mediated by alloreactive donor T cells after allogeneic bone marrow transplantation are limited by a concomitant decrease in graft-versus-tumor (GVT) activity and increased possibilities of tumor relapse. Using a novel approach, we adoptively transferred conventional T cells expressing the transcription factor promyelocytic leukemia zinc finger (PLZF), which confers effector properties resembling invariant natural killer T cells, such as copious production of cytokines under suboptimal stimulation. PLZF expression in T-cell allografts attenuates expansion of alloreactive T cells, leading to lower GVHD. Intact alloreactivity-driven antitumor cytokine responses result in preserved GVT effects, leading to improved survival. Our findings suggest that therapy with PLZF-overexpressing T cells would result in overall improved outcomes due to less GVHD and intact GVT effects.

Essentials of Th17 cell commitment and plasticity

CD4(+) T helper (Th) cells exist in a variety of epigenetic states that determine their function, phenotype, and capacity for persistence. These polarization states include Th1, Th2, Th17, and Foxp3(+) T regulatory cells, as well as the more recently described T follicular helper, Th9, and Th22 cells. Th17 cells express the master transcriptional regulator retinoic acid-related orphan receptor γ thymus and produce canonical interleukin (IL)-17A and IL-17F cytokines. Th17 cells display a great degree of context-dependent plasticity, as they are capable of acquiring functional characteristics of Th1 cells. This late plasticity may contribute to the protection against microbes, plays a role in the development of autoimmunity, and is necessary for antitumor activity of Th17 cells in adoptive cell transfer therapy models. Moreover, plasticity of this subset is associated with higher in vivo survival and self-renewal capacity and less senescence than Th1 polarized cells, which have less plasticity and more phenotypic stability. New findings indicate that subset polarization of CD4(+) T cells not only induces characteristic patterns of surface markers and cytokine production but also has a maturational aspect that affects a cell's ability to survive, respond to secondary stimulation, and form long-term immune memory.

Pharmacologic prophylaxis regimens for acute graft-versus-host disease: past, present and future

Abstract Acute graft-versus-host disease (GVHD) has compromised and continues to compromise the benefits associated with allogeneic hematopoietic cell transplant to cure malignant and non-malignant diseases. Pharmacologic interventions to prevent GVHD have emerged as a major objective of research in the immunology and transplant fields. A better understanding of the pathobiology behind the GVHD process has led the way to novel approaches and medications. Here we review the present arsenal of medications used to prevent GVHD, focusing on past experience and the current evidence, and discuss future potential targets.