Cutaneous GVHD is associated with the expansion of tissue-localized Th1 and not Th17 cells

Monocytes as an early risk factor for acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Acute graft-versus-host disease (aGVHD) is a major complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and contributes to high morbidity and mortality. However, our current understanding of the development and progression of aGVHD after allo-HSCT remains limited. To identify the potential biomarkers for the prevention and treatment of aGVHD during the early hematopoietic reconstruction after transplantation, we meticulously performed a comparative analysis of single-cell RNA sequencing data from post-transplant patients with or without aGVHD. Prior to the onset of aGVHD, monocytes in the peripheral blood of patients with aGVHD experienced a dramatic rise and activation on day 21 post-transplantation. This phenomenon is closely aligned with clinical cohort results obtained from blood routine examinations. Furthermore, in vitro co-culture experiments showed that peripheral blood monocytes extracted from patients with aGVHD approximately 21 days post-transplantation induced a significantly higher proliferation rate of allogeneic T cells compared to those from patients without aGVHD. Our study indicates that monocytes could be a crucial early clinical risk factor for the development of aGVHD, and this insight could potentially guide the timing of monitoring efforts, recommending assessments at the pivotal juncture of approximately day 21 post-transplantation, shedding fresh light on the significance of early hematopoietic regeneration in relation to the onset of aGVHD.

Efficiency and Toxicity of Imatinib Mesylate Combined with Atorvastatin Calcium in the Treatment of Steroid-Refractory Chronic Graft-versus-Host Disease: A Single-Center, Prospective, Single-Arm, Open-Label Study

INTRODUCTION

Steroid-refractory cGVHD (SR-cGVHD) presents new great challenges for treatment. We have reported that imatinib monotherapy was effective to SR-cGVHD, but the CR rate was not satisfactory and the benefit was not showed specific to some target organs, previously. Imatinib and statin drugs have been recognized to regulate T-cell function, statins also have been demonstrated endothelia protection, but whether this combination therapy was able to improve the efficacy remains unknown. Therefore, we designed this prospective, single-arm, open-label trial to investigate the efficacy of imatinib-based combination therapy in the treatment of SR-cGVHD for the first time.

METHODS

Sixty SR-cGVHD patients were entered into this trial to investigate the combination of imatinib mesylate and atorvastatin calcium for the treatment of SR-cGVHD. The primary endpoint included the overall response rate (ORR) after 6 months of combined treatment. The secondary endpoints included an evaluation of survival, changes in T-cell subsets, and adverse events.

RESULTS

At baseline, 45% (27/60) of patients had moderate cGVHD, and 55.0% (33/60) of patients had severe cGVHD. At the 6-month follow-up, a clinical response was achieved in 70.0% of patients, and a complete response (CR) was achieved in 26.7%. A total of 11.7% (7/60) of patients stopped immunosuppressive therapy at this point. After 6 months of treatment, the ORR rates of the liver, skin, eyes, and oral cavity were 80.6%, 78.1%, 61.5%, and 60.9%, respectively, with the liver also having the highest CR of 58.1%. The patients with moderate cGVHD had a better CR rate than those with severe cGVHD (55.6% vs. 3.0%, p < 0.0001). The overall survival in patients with ORR was improved (p = 0.0106). Lung involvement is an independent risk factor to affected ORR achievement (p = 0.021, HR = 0.335, 95% CI: 0.133-0.847), and the dosage of steroids was reduced in ORR patients. In clinical response patients, the ratio of CD8+ T cells (p = 0.0117) and Th17 cells (p = 0.0171) decreased, while the number of Treg cells (p = 0.0147) increased after 3 months. The most common adverse events were edema, nausea, and neutropenia, which were 13.3%, 11.7%, and 11.7%, respectively.

CONCLUSION

Combination treatment with imatinib mesylate and atorvastatin calcium was effective in treating SR-cGVHD and significantly decreased target organ injury, especially liver damage, indicating that T-cell regulatory function may play an important role in this process.

T helper 17 and regulatory T-cell profile and graft-versus-host disease after allogeneic hematopoietic stem cell transplantation in pediatric patients with beta-thalassemia

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective treatment option for hereditary hemoglobin disorders, such as beta-thalassemia; However, this procedure is not without constraints, mainly engendering complications such as acute graft-versus-host disease (aGvHD), chronic GvHD (cGvHD), and susceptibility to infections. The clinical outcomes of allo-HSCT are highly dependant on the quality and quantity of T-cell subsets reconstitution. Following the allo-HSCT of six pediatric patients afflicted with beta-thalassemia, their mononuclear cells were isolated, and then cultured with a combination of phorbol myristate acetate (PMA)/ionomycin and Brefeldin A. The content of CD4 T-cell subsets, including T helper 17 (Th17) cells and regulatory T cells (Tregs), were determined by specific conjugated-monoclonal antibodies three and six months post-HSCT. An increased frequency of total CD4 T-cells, Tregs and Th17 cells was observed at day 90 and 180 after allo-HSCT, albeit the numbers were still lower than that of our healthy controls. In patients who developed cGvHD, a lower Th17/Treg ratio was observed, owing it to a decreased proportion of Th17 cells. In conclusion, creating balance between Th17 and Treg subsets may prevent acute and chronic GvHD in patients after allo-HSCT.

60 Years Young: The Evolving Role of Allogeneic Hematopoietic Stem Cell Transplantation in Cancer Immunotherapy

The year 2020 marked the 30th anniversary of the Nobel Prize in Medicine awarded to E. Donnall Thomas for the development of allogeneic hematopoietic stem cell transplantation (allo-HSCT) to treat hematologic malignancies and other blood disorders. Dr. Thomas, "father of bone marrow transplantation," first developed and reported this technique in 1957, and in the ensuing decades, this seminal study has impacted fundamental work in hematology and cancer research, including advances in hematopoiesis, stem cell biology, tumor immunology, and T-cell biology. As the first example of cancer immunotherapy, understanding the mechanisms of antitumor biology associated with allo-HSCT has given rise to many of the principles used today in the development and implementation of novel transformative immunotherapies. Here we review the historical basis underpinning the development of allo-HSCT as well as advances in knowledge obtained by defining mechanisms of allo-HSCT activity. We review how these principles have been translated to novel immunotherapies currently utilized in clinical practice and describe potential future applications for allo-HSCT in cancer research and development of novel therapeutic strategies.

Histopathologic and immunophenotypic features of cutaneous solid organ transplant-associated graft-vs-host disease: Comparison with acute hematopoietic cell transplant-associated graft-vs-host disease and cutaneous drug eruption

BACKGROUND

Although it is relatively common after hematopoietic cell transplant (HCT), graft-vs-host disease (GVHD) is a rare complication following solid organ transplantation (SOT).

METHODS

This study evaluated skin biopsy specimens from five cases of SOT GVHD, 15 cases of HCT GVHD, and 15 cases of cutaneous drug eruption. Immunohistochemical staining for CD3, CD4, CD8, T-bet, and GATA-3 was performed to examine the density and immune phenotype of skin-infiltrating lymphocytes.

RESULTS

Similar to HCT GVHD, the predominant histopathologic findings in skin biopsy specimens of SOT GVHD were widespread vacuolar interface dermatitis with scattered necrotic keratinocytes. However, the density of dermal inflammation was considerably higher in SOT GVHD. Features that were more predictive of a cutaneous drug eruption over GVHD included spongiosis, confluent parakeratosis, and many eosinophils. Involvement of the hair follicle epithelium was seen in all three disorders. Both forms of cutaneous GVHD showed a predominance of Th1 (CD3+/T-bet+) lymphocytes within the inflammatory infiltrates. This shift was more pronounced in SOT GVHD, particularly among intraepidermal T-cells.

CONCLUSIONS

SOT GVHD shares many histopathologic features with HCT GVHD. However, SOT GVHD has a greater tendency to develop brisk lichenoid inflammation.

Removal of CD276+ cells from haploidentical memory T-cell grafts significantly lowers the risk of GVHD

Detrimental graft-versus-host disease (GVHD) still remains a major cause of death in hematopoietic stem cell transplantation (HSCT). The recently explored depletion of naive cells from mobilized grafts (CD45RA depletion) has shown considerable promise, yet is unable to eliminate the incidence of GVHD. Analysis of CD45RA-depleted haploidentical mixed lymphocytes culture (haplo-MLC) revealed insufficient suppression of alloresponses in the CD4⁺ compartment and identified CD276 as a marker for alloreactive memory Th1 T cells. Conclusively, depleting CD276⁺ cells from CD45RA-depleted haplo-MLC significantly attenuated alloreactivity to recipient cells while increasing antiviral reactivity and maintaining anti-third party reactivity in vitro. To evaluate these findings in vivo, bulk, CD45RA-depleted, or CD45RA/CD276-depleted CD4⁺ T cells from HLA-DR4^negative healthy humans were transplanted into NSG-Ab°DR4 mice, a sensitive human allo-GVHD model. Compellingly, CD45RA/CD276-depleted grafts from HLA-DR4^negative donors or in vivo depletion of CD276⁺ cells after transplant of HLA-DR4^negative memory CD4 T cells significantly delay the onset of GVHD symptoms and significantly alleviate its severity in NSG-Ab°DR4 mice. The clinical courses correlated with diminished Th1-cytokine secretion and downregulated CXCR6 expression of engrafted peripheral T cells. Collectively, mismatched HLA-mediated GVHD can be controlled by depleting recipient-specific CD276⁺ alloreacting T cells from the graft, highlighting its application in haplo-HSCT.

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.

Donor monocyte-derived macrophages promote human acute graft-versus-host disease

Myelopoiesis is invariably present and contributes to pathology in animal models of graft-versus-host disease (GVHD). In humans, a rich inflammatory infiltrate bearing macrophage markers has also been described in histological studies. In order to determine the origin, functional properties, and role in pathogenesis of these cells, we isolated single-cell suspensions from acute cutaneous GVHD and subjected them to genotype, transcriptome, and in vitro functional analysis. A donor-derived population of CD11c⁺CD14⁺ cells was the dominant population of all leukocytes in GVHD. Surface phenotype and NanoString gene expression profiling indicated the closest steady-state counterpart of these cells to be monocyte-derived macrophages. In GVHD, however, there was upregulation of monocyte antigens SIRPα and S100A8/9 transcripts associated with leukocyte trafficking, pattern recognition, antigen presentation, and costimulation. Isolated GVHD macrophages stimulated greater proliferation and activation of allogeneic T cells and secreted higher levels of inflammatory cytokines than their steady-state counterparts. In HLA-matched mixed leukocyte reactions, we also observed differentiation of activated macrophages with a similar phenotype. These exhibited cytopathicity to a keratinocyte cell line and mediated pathological damage to skin explants independently of T cells. Together, these results define the origin, functional properties, and potential pathogenic roles of human GVHD macrophages.

Th2 polarization in target organs is involved in the alleviation of pathological damage mediated by transplanting granulocyte colony-stimulating factor-primed donor T cells

Acute graft-versus-host disease (aGVHD) is caused by allo-activated donor T cells infiltrating target organs. As a regulator of immune function, granulocyte colony-stimulating factor (G-CSF) has been demonstrated to relieve the aGVHD reaction. However, the role of G-CSF-primed donor T cells in specific target organs is still unknown. In this study, we employed a classical MHC-mismatched transplantation mouse model (C57BL/6 into BALB/c) and found that recipient mice transplanted with G-CSF-primed T cells exhibited prolonged survival compared with that of the PBS-treated group. This protective function against GVHD mediated by G-CSF-primed donor T cells was further confirmed by decreased clinical and pathological scores in this aGVHD mouse model, especially in the lung and gut. Moreover, we found that T cells polarized towards Th2 cells and regulatory T cells were increased in specific target organs. In addition, G-CSF treatment inhibited inducible co-stimulator (ICOS) expression and increased the expression of tolerance-related genes in recipient mice. Our study provides new insight into the immune regulatory effects of G-CSF on T cell-mediated aGVHD, especially for its precise regulation in GVHD target organs.

β2-Adrenergic receptor activation on donor cells ameliorates acute GvHD

Acute graft versus host disease (aGvHD) remains a major impediment to successful allogeneic hematopoietic cell transplantation (allo-HCT). To solve this problem, a greater knowledge of factors that regulate the differentiation of donor T cells toward cytotoxic cells or Tregs is necessary. We report that the β2-adrenergic receptor (β2-AR) is critical for regulating this differentiation and that its manipulation can control aGvHD without impairing the graft-versus-tumor (GvT) effect. Donor T cell β2-AR expression and signaling is associated with decreased aGvHD when compared with recipients of β2-AR-/- donor T cells. We determined that β2-AR activation skewed CD4+ T cell differentiation in vitro and in vivo toward Tregs rather than the T helper 1 (Th1) phenotype. Treatment of allo-HCT recipients with a selective β2-agonist (bambuterol) ameliorated aGvHD severity. This was associated with increased Tregs, decreased cytotoxic T cells, and increased donor BM-derived myeloid-derived suppressor cells (MDSCs) in allogeneic and humanized xenogeneic aGvHD models. β2-AR signaling resulted in increased Treg generation through glycogen synthase kinase-3 activation. Bambuterol preserved the GvT effect by inducing NKG2D+ effector cells and central memory T cells. These data reveal how β-AR signaling can be targeted to ameliorate GvHD severity while preserving GvT effect.

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

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

Diverse Activity of IL-17+ Cells in Chronic Skin and Mucosa Graft-Versus-Host Disease

Excessive inflammatory environment in a course of chronic graft-versus-host disease (cGvHD) is associated with T-cell trafficking into inflamed tissues. This study focused on the identification of IL-17-producing cells in the tissue biopsies of cGvHD patients. Forty-one biopsy specimens of cGvHD lesions of the skin (n = 27), gastrointestinal tract (n = 9) and oral mucosa (n = 5), examined in 24 patients, were morphologically defined according to the NIH criteria and analyzed for the presence of cellular infiltrations including: IL-17⁺, FOXP3⁺ and CCR6⁺ cells. IL-17⁺ cells were identified in 26/27 skin and in all gut and oral mucosa biopsies, being more frequent in mucosa lesions than in the skin (11/14 vs 14/26, respectively; NS: not significant). Double staining documented that CD138⁺/IL-17⁺ cells were commonly seen in the gut than in the skin (5/8 vs 3/11, respectively; NS). In the skin, cells expressing trafficking receptor CCR6⁺ were more frequent than IL-17⁺ cells compared to the mucosa (23/26 vs 2/13, respectively; p < 0.0001). CCR6 was present on a majority of IL-17⁺ cells in all examined skin biopsies but only in 6 out of 11 digestive tract biopsies (p = 0.0112). FOXP3⁺ cells were identified only in five patients (with mild lesions) at least in one biopsy. In this study group, results documented that local expansion of IL-17-producing cells in the digestive tract correlate with moderate and severe clinical symptoms of cGvHD, in contrast to the skin, where IL-17⁺ cells are rather scarcely present (p = 0.0301) and the course of cGvHD is slowly progressing with final organ deterioration.

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.

An activated Th17-prone T cell subset involved in chronic graft-versus-host disease sensitive to pharmacological inhibition

Chronic graft-versus-host disease (cGvHD) remains a major complication of allogeneic stem cell transplantation requiring novel therapies. CD146 and CCR5 are expressed by activated T cells and associated with increased T cell migration capacity and Th17 polarization. We performed a multiparametric flow cytometry analysis in a cohort of 40 HSCT patients together with a cGvHD murine model to understand the role of CD146-expressing subsets. We observed an increased frequency of CD146+ CD4 T cells in the 20 patients with active cGvHD with enhanced RORγt expression. This Th17-prone subset was enriched for cells coexpressing CD146 and CCR5 that harbor mixed Th1/Th17 features and were more frequent in cGvHD patients. Utilizing a murine cGvHD model with bronchiolitis obliterans (BO), we observed that donor T cells from CD146-deficient mice versus those from WT mice caused significantly reduced pulmonary cGvHD. Reduced cGvHD was not the result of failed germinal center B cell or T follicular helper cell generation. Instead, CD146-deficient T cells had significantly lower pulmonary macrophage infiltration and T cell CCR5, IL-17, and IFN-γ coexpression, suggesting defective pulmonary end-organ effector mechanisms. We, thus, evaluated the effect of TMP778, a small-molecule RORγt activity inhibitor. TMP778 markedly alleviated cGvHD in murine models similarly to agents targeting the Th17 pathway, such as STAT3 inhibitor or IL-17-blocking antibody. Our data suggest CD146-expressing T cells as a cGvHD biomarker and suggest that targeting the Th17 pathway may represent a promising therapy for cGvHD.

Tbet is a critical modulator of FoxP3 expression in autoimmune graft-versus-host disease

CD4⁺ T-helper subsets drive autoimmune chronic graft-versus-host disease, a major complication after allogeneic bone marrow transplantation. However, it remains unclear how specific T-helper subsets contribute to chronic graft-versus-host disease. T-helper type 1 cells are one of the major disease-mediating T-cell subsets and require interferon-γ signaling and Tbet expression for their function. Regulatory T cells on the other hand can inhibit T-helper type 1 cell-mediated responses. Using an established murine model that isolates the autoimmune component of graft-versus-host disease, we hypothesized that T-helper type 1 cells would restrict FoxP3-driven regulatory T cells. Upon transfer into immune-deficient syngeneic hosts, alloreactive Tbx21^−/−CD4⁺ T cells led to marked increases in FoxP3⁺ cells and reduced clinical evidence of autoimmunity. To evaluate whether peripheral induction contributed to regulatory T-cell predominance, we adoptively transferred Tbx21^−/− T cells that consisted of fate mapping for FoxP3: recipients of flow-purified effector cells that were Foxp3⁻ and Tbx21^−/− had enhanced T-regulatory-cell predominance during autoimmune graft-versus-host disease. These data directly demonstrated that peripheral T-regulatory-cell induction was inhibited by Tbet. Finally, Tbx21^−/− T-regulatory cells cross-regulated autoimmune wild-type T-effector-cell cytokine production in vivo. The Tbet pathway therefore directly impairs T-regulatory-cell reconstitution and is consequently a feasible target in efforts to prevent autoimmune graft-versus-host disease.

Rat acute GvHD is Th1 driven and characterized by predominant donor CD4+ T-cell infiltration of skin and gut

Acute graft-versus-host disease (aGvHD) remains a significant hurdle to successful treatment of many hematological disorders. The disease is caused by infiltration of alloactivated donor T cells primarily into the gastrointestinal tract and skin. Although cytotoxic T cells mediate direct cellular damage, T helper (Th) cells differentially secrete immunoregulatory cytokines. aGvHD is thought to be initiated primarily by Th1 cells but a consensus is still lacking regarding the role of Th2 and Th17 cells. The aim of this study was to determine the contribution of distinct T-cell subsets to aGvHD in the rat. aGvHD was induced by transplanting irradiated rats with T-cell-depleted major histocompatibility complex-mismatched bone marrow, followed 2 weeks later by donor lymphocyte infusion. Near complete donor T-cell chimerism was achieved in the blood and lymphatic tissues, in contrast to mixed chimerism in the skin and gut. Skin and gut donor T cells were predominantly CD4⁺, in contrast to T cells in the blood and lymphatic tissues. Genes associated with Th1 cells were upregulated in gut, liver, lung, and skin tissues affected by aGvHD. Increased serum levels of CXCL10 and IL-18 preceded symptoms of aGvHD, accompanied by increased responsiveness to CXCL10 by blood CD4⁺ T cells. No changes in the expression of Th2- or Th17-associated genes were observed, indicating that aGvHD in this rat model is mainly Th1 driven. The rat model of aGvHD could be instrumental for further investigations of donor T-cell subsets in the skin and gut and for exploring therapeutic options to ameliorate symptoms of aGvHD.

A high migratory capacity of donor T-cells in response to the lymph node homing receptor CCR7 increases the incidence and severity of GvHD

The pathogenesis of GvHD involves migration of donor T-cells into the secondary lymphoid organs in the recipient, which is steered by two homing molecules, CD62L and CCR7. Therefore, we investigated whether the migratory capacity of donor T-cells is associated with GvHD. This single center prospective study included 85 donor-recipient pairs. In vitro chemotaxis assays of the lymphocytes of the apheresis product were performed in parallel to the analysis of CD62L and CCR7 by flow cytometry. The migratory index to the CCR7 ligands, CCL19 and CCL21, was higher in T-cells from donors whose recipients will develop GvHD. Similarly, the acute GvHD (aGvHD) group received higher percentage of CD4+CCR7+ T-cells, whereas chronic GvHD (cGvHD) patients were transplanted with higher percentages of CD8+CCR7+ T-cells compared with the non-GvHD group. These results were confirmed when patients were subdivided according to degrees of severity. Further, multivariate analysis confirmed that the proportions of CCR7+ CD4+ and CCR7+ CD8+ T-cells are risk factors for the development and severity of aGvHD and cGvHD, respectively. Functional experiments demonstrated that CCR7+ T-cells exhibited higher potential for activation than CCR7- T-cells did. We therefore propose that the selective depletion of CCR7-expressing T-cells may be an effective preventive therapy for GvHD.

Role of CD8 Regulatory T Cells versus Tc1 and Tc17 Cells in the Development of Human Graft-versus-Host Disease

CD8⁺ T cells that secrete proinflammatory cytokines play a central role in exacerbation of inflammation; however, a new subpopulation of CD8 regulatory T cells has recently been characterized. This study analyzes the prominent role of these different subpopulations in the development of graft-versus-host disease (GVHD). Samples from 8 healthy donors mobilized with Filgrastim® (G-CSF) and 18 patients who underwent allogeneic hematopoietic stem cell transplantation (HSCT) were evaluated by flow cytometry. Mobilization induced an increase in Tc1 (p < 0.01), Th1 (p < 0.001), Tc17 (p < 0.05), and CD8⁺IL-10⁺ cells (p < 0.05), showing that G-CSF induces both pro- and anti-inflammatory profiles. Donor-patient correlation revealed a trend (p = 0.06) toward the development of GVHD in patients who receive a high percentage of Tc1 cells. Patients with acute GVHD (aGVHD), either active or controlled, and patients without GVHD were evaluated; patients with active aGVHD had a higher percentage of Tc1 (p < 0.01) and Tc17 (p < 0.05) cells, as opposed to patients without GVHD in whom a higher percentage of CD8 Treg cells (p < 0.01) was found. These findings indicate that the increase in Tc1 and Tc17 cells is associated with GVHD development, while regulatory CD8 T cells might have a protective role in this disease. These tests can be used to monitor and control GVHD.

Chronic graft-versus-host disease: biological insights from preclinical and clinical studies

With the increasing use of mismatched, unrelated, and granulocyte colony-stimulating factor-mobilized peripheral blood stem cell donor grafts and successful treatment of older recipients, chronic graft-versus-host disease (cGVHD) has emerged as the major cause of nonrelapse mortality and morbidity. cGVHD is characterized by lichenoid changes and fibrosis that affects a multitude of tissues, compromising organ function. Beyond steroids, effective treatment options are limited. Thus, new strategies to both prevent and treat disease are urgently required. Over the last 5 years, our understanding of cGVHD pathogenesis and basic biology, born out of a combination of mouse models and correlative clinical studies, has radically improved. We now understand that cGVHD is initiated by naive T cells, differentiating predominantly within highly inflammatory T-helper 17/T-cytotoxic 17 and T-follicular helper paradigms with consequent thymic damage and impaired donor antigen presentation in the periphery. This leads to aberrant T- and B-cell activation and differentiation, which cooperate to generate antibody-secreting cells that cause the deposition of antibodies to polymorphic recipient antigens (ie, alloantibody) or nonpolymorphic antigens common to both recipient and donor (ie, autoantibody). It is now clear that alloantibody can, in concert with colony-stimulating factor 1 (CSF-1)-dependent donor macrophages, induce a transforming growth factor β-high environment locally within target tissue that results in scleroderma and bronchiolitis obliterans, diagnostic features of cGVHD. These findings have yielded a raft of potential new therapeutics, centered on naive T-cell depletion, interleukin-17/21 inhibition, kinase inhibition, regulatory T-cell restoration, and CSF-1 inhibition. This new understanding of cGVHD finally gives hope that effective therapies are imminent for this devastating transplant complication.

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.

Therapeutics for Graft-versus-Host Disease: From Conventional Therapies to Novel Virotherapeutic Strategies

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has a curative potential for many hematologic malignancies and blood diseases. However, the success of allo-HSCT is limited by graft-versus-host disease (GVHD), an immunological syndrome that involves inflammation and tissue damage mediated by donor lymphocytes. Despite immune suppression, GVHD is highly incident even after allo-HSCT using human leukocyte antigen (HLA)-matched donors. Therefore, alternative and more effective therapies are needed to prevent or control GVHD while preserving the beneficial graft-versus-cancer (GVC) effects against residual disease. Among novel therapeutics for GVHD, oncolytic viruses such as myxoma virus (MYXV) are receiving increased attention due to their dual role in controlling GVHD while preserving or augmenting GVC. This review focuses on the molecular basis of GVHD, as well as state-of-the-art advances in developing novel therapies to prevent or control GVHD while minimizing impact on GVC. Recent literature regarding conventional and the emerging therapies are summarized, with special emphasis on virotherapy to prevent GVHD. Recent advances using preclinical models with oncolytic viruses such as MYXV to ameliorate the deleterious consequences of GVHD, while maintaining or improving the anti-cancer benefits of GVC will be reviewed.

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.

Tear Cytokines as Biomarkers for Chronic Graft-versus-Host Disease

We investigated the tear cytokine profiles in patients who underwent stem cell transplantation (SCT) and attempted to evaluate whether tear cytokines are associated with the presence of systemic chronic graft-versus-host disease (GVHD), regardless of ocular GVHD status. We also tested tear cytokines as biomarkers for chronic ocular GVHD severity. Forty-four patients who underwent SCT were enrolled and their diagnosis of chronic GVHD was confirmed. Ocular surface parameters and tear cytokine profiles were evaluated and the correlations between concentrations of cytokines and ocular surface parameters or several chronic ocular GVHD severity scales were evaluated. Tear interleukin (IL)-2, IL-10, IL-17α, interferon (IFN)-γ, IL-6, and tumor necrosis factor (TNF)-α were elevated in patients with chronic systemic GVHD compared with patients without chronic systemic GVHD. Receiver-operating characteristic curve analysis revealed that area under the curve (AUC) values for tear IL-10 (AUC = .795), IL-17α (AUC = .821), IL-6 (AUC = .912), and TNF-α (AUC = .910) were significantly correlated with the presence of chronic GVHD (all P < .001). Tear IL-10, IL-6, and TNF-α showed a stronger correlation with ocular surface parameters than other cytokines and these cytokines also correlated with several chronic ocular GVHD severity scales (all P < .05). Our data suggest the tear cytokines are useful biomarkers for the diagnosis of chronic GVHD after SCT and chronic ocular GVHD severity.

Approaches for the prevention of graft-versus-host disease following hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (HCT) is an important therapeutic option for malignant and non-malignant diseases, but the more widespread application of the therapy remains limited by the occurrence of graft versus host disease (GVHD). GVHD results from immune-mediated injury by donor immune cells against tissues in the HCT recipient, and can be characterized as acute or chronic depending on the time of onset and site of organ involvement. The majority of efforts have focused on GVHD prevention. Calcineurin inhibitors are the most widely used agents and are included in almost all regimens. Despite current prophylaxis strategies, 40-70% of patients remain at risk for developing GVHD. Herein, we review standard and emerging therapies used in GVHD management.

Valproic Acid Ameliorates Graft-versus-Host Disease by Downregulating Th1 and Th17 Cells

Graft-versus-host disease (GVHD) is the major complication after allogeneic bone marrow transplantation. Valproic acid (VPA) was described as a histone deacetylase inhibitor that had anti-inflammatory effects and reduced the production of proinflammatory cytokines in experimental autoimmune disease models. Using well-characterized mouse models of MHC-mismatched transplantation, we studied the effects of VPA on GVHD severity and graft-versus-leukemia (GVL) activity. Administration of VPA significantly attenuated the clinical severity of GVHD, the histopathology of GVHD-involved organs, and the overall mortality from GVHD. VPA downregulated Th1 and Th17 cell responses and cytokine production in vitro and in vivo, whereas its effect on GVHD was regulatory T cell independent. The effect of VPA was related to its ability to directly reduce the activity of Akt, an important regulator of T cell immune responses. Importantly, when mice received lethal doses of host-type acute leukemia cells, administration of VPA did not impair GVL activity and resulted in significantly improved leukemia-free survival. These findings reveal a unique role for VPA as a histone deacetylase inhibitor in reducing the donor CD4(+) T cells that contribute to GVHD, which may provide a strategy to reduce GVHD while preserving the GVL effect.

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.

Clinical perspectives and murine models of lichenoid tissue reaction/interface dermatitis

A set of histopathological elements, that is death of epidermal basal cell layer keratinocytes and inflammatory cell infiltration, distinguishes lichenoid tissue reaction (LTR)/interface dermatitis (IFD) from other inflammatory mucocutaneous diseases with histological findings of superficial perivascular dermatitis. The LTR/IFD is observed in inflammatory mucocutaneous diseases such as lichen planus, Stevens-Johnson syndrome/toxic epidermal necrolysis, acute graft-versus-host disease, lupus erythematosus and dermatomyositis. Clinical and basic researches have suggested that keratinocytes are antigen-presenting cells and mediate LTR/IFD reaction via production of cytokines/chemokines and inhibitory molecules such as programmed cell death (PD)-L1, and that cytotoxic CD8(+) T cells producing cytotoxic granules, perforin, granzyme B and granulysin are final effector cells to cause keratinocyte death. Because interferon-γ and FasL, which are produced by not only CD8(+) but also CD4(+) T cells, are candidates of the pathogenic molecules in LTR/IFD, CD4(+) T cells may also play a role to develop LTR/IFD. On the other hand, CD4(+) Treg cells accelerate the remission of LTR/IFD. Some murine models of LTR/IFD have been established. For example, LTR/IFD reactions were induced in keratinocyte-specific membrane-binding ovalbumin-transgenic (mOVA Tg) mice by adoptive transfer of CD8(+) T cells with OVA-specific T-cell-receptor. It has also been shown that human CD8(+) T cells are pathogenic immune cells in human skin-xenografted mice. Various immunosuppressants are used to treat patients with mucocutaneous diseases with LTR/IFD. By analysis of the mOVA Tg mice, a JAK inhibitor was suggested to be a new candidate drug to inhibit not only pathogenic T cells but also keratinocyte death in LTR/IFD. More specific treatments for patients with LTR/IFD will be developed in future.

Regulatory T cells produce profibrotic cytokines in the skin of patients with systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is an autoimmune disorder characterized by fibrosis of the skin and internal organs. Pathologic conversion of regulatory T (Treg) cells into inflammatory cytokine-producing cells is thought to be an important step in the progression of autoimmunity, but whether loss of normal Treg cell function contributes to SSc is unknown.

OBJECTIVE

We sought to determine whether Treg cells in the blood and skin of patients with SSc acquired abnormal production of effector cytokines.

METHODS

Peripheral blood and skin biopsy specimens were collected from control subjects and patients with limited or diffuse SSc. Flow cytometry was used to evaluate expression of cell-surface proteins and the cytokine production profile of forkhead box protein 3-positive Treg cells compared with forkhead box protein 3-negative conventional T cells.

RESULTS

Treg cells in the blood of patients with SSc had a normal phenotype and did not produce T-effector cytokines. In contrast, Treg cells from skin affected by SSc produced significant amounts of IL-4 and IL-13. Although Treg cells in the blood of patients with SSc did not make TH2 cytokines, they contained a significantly higher proportion of skin-homing cells expressing TH2 cell-associated chemokine receptors. Evidence that IL-33 caused the differentiation of skin Treg cells into TH2-like cells, combined with high tissue-localized expression of this cytokine in patients with SSc and expression of the ST2 chain of the IL-33 receptor on skin-localized Treg cells, suggests that IL-33 might be an important stimulator of tissue-localized loss of normal Treg cell function.

CONCLUSION

These data are the first evidence for the presence of TH2-like Treg cells in human autoimmunity and show that Treg cell plasticity can be tissue specific. Localized dysfunction of Treg cells is a previously unknown factor that might contribute to fibrosis in patients with SSc.

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.

Control of tissue-localized immune responses by human regulatory T cells

Treg cells control immune responses to self and nonharmful foreign antigens. Emerging data from animal models indicate that Treg cells function in both secondary lymphoid organs and tissues, and that these different microenvironments may contain specialized subsets of Treg cells with distinct mechanisms of action. The design of therapies for the restoration of tissue-localized immune homeostasis is dependent upon understanding how local immune responses are influenced by Treg cells in health versus disease. Here we review the current state of knowledge about human Treg cells in four locations: the skin, lung, intestine, and joint. Despite the distinct biology of these tissues, there are commonalities in the biology of their resident Treg cells, including phenotypic and functional differences from circulating Treg cells, and the presence of cytokine-producing (e.g. IL-17(+)) FOXP3(+) cells. We also highlight the challenges to studying tissue Treg cells in humans, and opportunities to use new technologies for the detailed analysis of Treg cells at the single-cell level. As emerging biological therapies are increasingly targeted toward tissue-specific effects, it is critical to understand their potential impact on local immune regulation.

Monocyte-induced development of Th17 cells and the release of S100 proteins are involved in the pathogenesis of graft-versus-host disease

Graft-versus-host disease (GvHD) is a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation. However, the pathophysiology of GvHD remains poorly understood. In this study, we analyzed the induction of Th17 cells by monocytes of patients with GvHD in vitro, demonstrating that monocytes isolated from patients with acute skin and intestinal GvHD stage I-IV and chronic GvHD induce significantly increased levels of Th17 cells compared with patients without GvHD. S100 proteins are known to act as innate amplifier of inflammation. We therefore investigated the presence of S100 proteins in the stool, serum, and bowel tissue of patients with GvHD and the influence of S100 proteins on the induction of Th17 cells. Elevated levels of S100 proteins could be detected in patients with acute GvHD, demonstrating the release of these phagocyte-specific proteins during GvHD. Furthermore, stimulation of monocytes with S100 proteins was found to promote Th17 development, emphasizing the role of S100 proteins in Th17-triggered inflammation. Altogether, our results indicate that induction of Th17 cells by activated monocytes and the stimulatory effects of proinflammatory S100 proteins might play a relevant role in the pathogenesis of acute GvHD. Regarding our data, S100 proteins might be novel markers for the diagnosis and follow-up of GvHD.

Current issues in chronic graft-versus-host disease

Chronic graft-versus-host disease (GVHD) is a frequent and potentially life-threatening complication of allogeneic hematopoietic stem cell transplantation. Increased transplantation of older patients and the more frequent use of unrelated donors has led to increased numbers of patients with this painful complication. Recent advances have been made in understanding the pathophysiology of chronic GVHD and in establishing precise criteria for diagnosis and classification of disease manifestations. These advances will hopefully pave the way for improving both the prophylaxis and treatment of chronic GVHD.

Current issues in chronic graft-versus-host disease

Chronic graft-versus-host disease (GVHD) is a frequent and potentially life-threatening complication of allogeneic hematopoietic stem cell transplantation. Increased transplantation of older patients and the more frequent use of unrelated donors has led to increased numbers of patients with this painful complication. Recent advances have been made in understanding the pathophysiology of chronic GVHD and in establishing precise criteria for diagnosis and classification of disease manifestations. These advances will hopefully pave the way for improving both the prophylaxis and treatment of chronic GVHD.

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.

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.

Diverse T-cell responses characterize the different manifestations of cutaneous graft-versus-host disease

Graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic stem cell transplantation (HCT) and can present in an acute (aGVHD), a chronic lichenoid (clGVHD), and a chronic sclerotic form (csGVHD). It is unclear whether similar or different pathomechanisms lead to these distinct clinical presentations. To address this issue, we collected lesional skin biopsies from aGVHD (n = 25), clGVHD (n = 17), and csGVHD (n = 7) patients as well as serial nonlesional biopsies from HCT recipients (prior to or post-HCT) (n = 14) and subjected them to phenotypic and functional analyses. Our results revealed striking differences between aGVHD and clGVHD. In aGVHD, we found a clear predominance of T helper (Th)2 cytokines/chemokines and, surprisingly, of interleukin (IL)-22 messenger RNA as well as an increase of IL-22-producing CD4(+) T cells. Thymic stromal lymphopoietin, a cytokine skewing the immune response toward a Th2 direction, was elevated at day 20 to 30 post-HCT in the skin of patients who later developed aGVHD. In sharp contrast to aGVHD, the immune response occurring in clGVHD showed a mixed Th1/Th17 signature with upregulated Th1/Th17 cytokine/chemokine transcripts and elevated numbers of interferon-γ- and IL-17-producing CD8(+) T cells. Our findings shed new light on the T-cell responses involved in the different manifestations of cutaneous GVHD and identify molecular signatures indicating the development of the disease.

Increased plasmacytoid dendritic cells and RORγt-expressing immune effectors in cutaneous acute graft-versus-host disease

The role of PDCs and Th17 cells is not well understood in the pathogenesis of aGVHD. We evaluated PDC and Th17 cells in skin biopsies of 38 patients at diagnosis of aGVHD. The biopsies were tested by immunohistochemistry for the expression of BDCA2, a typical marker of PDCs. We found an increase of BDCA2(+) cells in the skin of the patients with aGVHD. Moreover, we observed a strong expression of the type I IFN-inducible protein Mx1 in the skin of the patients with aGVHD, compared with that of those without it, suggesting that PDCs produce type I IFN. We also analyzed the expression of two Th17 surface markers-CD161 and CCR6-and RORγt, the key transcription factor that orchestrates the differentiation of Th17 cells. Significantly higher numbers of RORγt(+), CD161(+), and CCR6(+) cells were counted in the skin of the patients with aGVHD than in the skin of those who underwent allo-SCT and in whom aGVHD did not develop. This study provides evidence for a role of Th17-mediated responses and a potential new pathophysiological link between PDCs and Th17 in human cutaneous aGVHD.

Transcriptome analysis reveals markers of aberrantly activated innate immunity in vitiligo lesional and non-lesional skin

BACKGROUND

Vitiligo is characterized by the death of melanocytes in the skin. This is associated with the presence of T cell infiltrates in the lesional borders. However, at present, there is no detailed and systematic characterization on whether additional cellular or molecular changes are present inside vitiligo lesions. Further, it is unknown if the normal appearing non-lesional skin of vitiligo patients is in fact normal. The purpose of this study is to systematically characterize the molecular and cellular characteristics of the lesional and non-lesional skin of vitiligo patients.

METHODS AND MATERIALS

Paired lesional and non-lesional skin biopsies from twenty-three vitiligo patients and normal skin biopsies from sixteen healthy volunteers were obtained with informed consent. The following aspects were analyzed: (1) transcriptome changes present in vitiligo skin using DNA microarrays and qRT-PCR; (2) abnormal cellular infiltrates in vitiligo skin explant cultures using flow cytometry; and (3) distribution of the abnormal cellular infiltrates in vitiligo skin using immunofluorescence microscopy.

RESULTS

Compared with normal skin, vitiligo lesional skin contained 17 genes (mostly melanocyte-specific genes) whose expression was decreased or absent. In contrast, the relative expression of 13 genes was up-regulated. The up-regulated genes point to aberrant activity of the innate immune system, especially natural killer cells in vitiligo. Strikingly, the markers of heightened innate immune responses were also found to be up-regulated in the non-lesional skin of vitiligo patients.

CONCLUSIONS AND CLINICAL IMPLICATIONS

As the first systematic transcriptome characterization of the skin in vitiligo patients, this study revealed previously unknown molecular markers that strongly suggest aberrant innate immune activation in the microenvironment of vitiligo skin. Since these changes involve both lesional and non-lesional skin, our results suggest that therapies targeting the entire skin surface may improve treatment outcomes. Finally, this study revealed novel mediators that may facilitate future development of vitiligo therapies.

Decreased levels of circulating IL17-producing CD161+CCR6+ T cells are associated with graft-versus-host disease after allogeneic stem cell transplantation

The C-type lectin-like receptor CD161 is a well-established marker for human IL17-producing T cells, which have been implicated to contribute to the development of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (allo-SCT). In this study, we analyzed CD161⁺ T cell recovery, their functional properties and association with GVHD occurrence in allo-SCT recipients. While CD161⁺CD4⁺ T cells steadily recovered, CD161^hiCD8⁺ T cell numbers declined during tapering of Cyclosporine A (CsA), which can be explained by their initial growth advantage over CD161^neg/lowCD8⁺ T cells due to ABCB1-mediated CsA efflux. Interestingly, occurrence of acute and chronic GVHD was significantly correlated with decreased levels of circulating CD161⁺CD4⁺ as well as CD161^hiCD8⁺ T cells. In addition, these subsets from transplanted patients secreted high levels of IFNγ and IL17. Moreover, we found that CCR6 co-expression by CD161⁺ T cells mediated specific migration towards CCL20, which was expressed in GVHD biopsies. Finally, we demonstrated that CCR6⁺ T cells indeed were present in these CCL20⁺ GVHD-affected tissues. In conclusion, we showed that functional CD161⁺CCR6⁺ co-expressing T cells disappear from the circulation and home to GVHD-affected tissue sites. These findings support the hypothesis that CCR6⁺CD161-expressing T cells may be involved in the immune pathology of GVHD following their CCL20-dependent recruitment into affected tissues.

Inorganic arsenic represses interleukin-17A expression in human activated Th17 lymphocytes

Trivalent inorganic arsenic [As(III)] is an efficient anticancer agent used to treat patients suffering from acute promyelocytic leukemia. Recently, experimental studies have clearly demonstrated that this metalloid can also cure lymphoproliferative and/or pro-inflammatory syndromes in different murine models of chronic immune-mediated diseases. T helper (Th) 1 and Th17 lymphocytes play a central role in development of these diseases, in mice and humans, especially by secreting the potent pro-inflammatory cytokine interferon-γ and IL-17A, respectively. As(III) impairs basic functions of human T cells but its ability to modulate secretion of pro-inflammatory cytokines by differentiated Th lymphocytes is unknown. In the present study, we demonstrate that As(III), used at concentrations clinically achievable in plasma of patients, has no effect on the secretion of interferon-γ from Th1 cells but almost totally blocks the expression and the release of IL-17A from human Th17 lymphocytes co-stimulated for five days with anti-CD3 and anti-CD28 antibodies, in the presence of differentiating cytokines. In addition, As(III) specifically reduces mRNA levels of the retinoic-related orphan receptor (ROR)C gene which encodes RORγt, a key transcription factor controlling optimal IL-17 expression in fully differentiated Th17 cells. The metalloid also blocks initial expression of IL-17 gene induced by the co-stimulation, probably in part by impairing activation of the JNK/c-Jun pathway. In conclusion, our results demonstrate that As(III) represses expression of the major pro-inflammatory cytokine IL-17A produced by human Th17 lymphocytes, thus strengthening the idea that As(III) may be useful to treat inflammatory immune-mediated diseases in humans.