Fluctuations in pathogenic CD4+ T-cell subsets in a murine sclerodermatous model of chronic graft-versus-host disease

Preclinical evaluation of JAK1/2 inhibition by ruxolitinib in a murine model of chronic graft-versus-host disease

The objective of this study was to examine the therapeutic effect of ruxolitinib, an orally administered selective Janus kinase (JAK) 1/2 inhibitor, on chronic graft-versus-host disease (cGVHD) using a murine model of sclerodermatous GVHD (scl-GVHD). Compared with scl-GVHD controls, ruxolitinib-treated recipients had scl-GVHD of significantly attenuated clinical and pathological severity in the skin and decreased frequencies of effector cells, CD4⁺ T cells, and CD11b⁺ macrophage/monocytes. Regulatory CD4⁺ Foxp3⁺ T cells were expanded whereas interferon-γ (IFN-γ)-producing CD4⁺ T cells were significantly decreased in ruxolitinib-treated recipients. Ruxolitinib suppressed not only the production of IFN-γ from CD4⁺ T cells and monocyte chemoattractant protein 1 (MCP-1) from CD11b⁺ macrophage/monocytes, but also the proliferation of these cells in vitro. Levels of both cytokines (IFN-γ and MCP-1) were also reduced in the spleen and skin of ruxolitinib-treated recipients in vivo. IFN-γ-induced MCP-1 production and migration of RAW 264.7 cells, a macrophage cell line, were inhibited by ruxolitinib. However, supplementation with MCP-1 restored this effect of ruxolitinib. In addition, blocking JAK-STAT signaling using ruxolitinib reduced the activation of STAT1 in stimulated immune effector cells. Taken together, these results suggest that ruxolitinib can prevent scl-GVHD by suppressing IFN-γ produced by T cells and MCP-1 expression in macrophage/monocytes via inhibition of JAK-STAT signaling.

Cholinergic modulation of the immune system - A novel therapeutic target for myocardial inflammation

The immune system and the nervous system depend on each other for their fine tuning and working, thus cooperating to maintain physiological homeostasis and prevent infections. The cholinergic system regulates the mobilization, differentiation, secretion, and antigen presentation of adaptive and innate immune cells mainly through α7 nicotinic acetylcholine receptors (α7nAChRs). The neuro-immune interactions are established and maintained by the following mechanisms: colocalization of immune and neuronal cells at defined anatomical sites, expression of the non-neuronal cholinergic system by immune cells, and the acetylcholine receptor-mediated activation of intracellular signaling pathways. Based on these immunological mechanisms, the protective effects of cholinergic system in animal models of diseases were summarized in this paper, such as myocardial infarction/ischemia-reperfusion, viral myocarditis, and endotoxin-induced myocardial damage. In addition to maintaining hemodynamic stability and improving the energy metabolism of the heart, both non-neuronal acetylcholine and neuronal acetylcholine in the heart can alleviate myocardial inflammation and remodeling to exert a significant cardioprotective effect. The new findings on the role of cholinergic agonists and vagus nerve stimulation in immune regulation are updated, so as to develop improved approaches to treat inflammatory heart disease.

CCL1 blockade alleviates human mesenchymal stem cell (hMSC)-induced pulmonary fibrosis in a murine sclerodermatous graft-versus-host disease (Scl-GVHD) model

Background

Human chronic graft-versus-host disease (CGVHD) shares clinical characteristics with a murine sclerodermatous GVHD (Scl-GVHD, B10.D2 → BALB/c) model that is characterized by skin and lung fibrosis. In this study, bone marrow- or adipose tissue-derived human mesenchymal stem cells (hMSCs) were injected into the Scl-GVHD mice to address their therapeutic effect on CGVHD.

Methods

Lethally irradiated BALB/c mice were transplanted with B10.D2 T cell-depleted bone marrow with or without spleen cells to generate Scl-GVHD. hMSCs were intravenously treated on days 3, 5, and 7 post-transplantation, and the control antibody or CCL1 blocking antibody was subcutaneously injected according to the same schedule as the hMSCs. Fourteen days after transplantation, the recipient mice were sacrificed, and their skin and lungs were analyzed.

Results

After the early injection of hMSCs after transplantation, the clinical and pathological severity of Scl-GVHD in the skin was significantly attenuated, whereas the pathological score was exacerbated in the lungs. hMSCs had migrated into the lungs, but not into the skin. CD11b monocyte/macrophages and CD4 T cells were markedly decreased in skin tissues, whereas there was an early recruitment of CD11b cells, and subsequently increased infiltration of CD4 T cells, in the lungs. Importantly, hMSCs persistently upregulated the expression of CCL1 in the lungs, but not in the skin. Concurrent treatment of hMSCs with a CCL1-blocking antibody alleviated the severity of the lung histopathology score and fibrosis with the preservation of the cutaneous protective effect against CGVHD. Infiltration of CD3 T cells and CD68 macrophages and upregulation of chemokines were also decreased in lung tissues, along with the recruitment of eosinophils and tissue IgE expression. In the skin, chemokine expression was further reduced after CCL1 blockade.

Conclusions

These data demonstrate that despite a protective effect against Scl-GVHD in the skin, administration of hMSCs exacerbated lung fibrosis associated with eosinophilia and airway inflammation through persistent CCL1 upregulation. CCL1 blockade offers a potential treatment of pulmonary complications induced after treatment with hMSCs.

Inducible T-Cell Co-Stimulator Impacts Chronic Graft-Versus-Host Disease by Regulating Both Pathogenic and Regulatory T Cells

The incidence of chronic graft-versus-host disease (cGVHD) is on the rise and still the major cause of morbidity and mortality among patients after allogeneic hematopoietic stem cell transplantation (HCT). Both donor T and B cells contribute to the pathogenesis of cGVHD. Inducible T-cell co-stimulator (ICOS), a potent co-stimulatory receptor, plays a key role in T-cell activation and differentiation. Yet, how ICOS regulates the development of cGVHD is not well understood. Here, we investigated the role of ICOS in cGVHD pathogenesis using mice with germline or regulatory T cell (Treg)-specific ICOS deficiency. The recipients of ICOS^−/− donor grafts had reduced cGVHD compared with wild-type controls. In recipients of ICOS^−/− donor grafts, we observed significant reductions in donor T follicular helper (Tfh), Th17, germinal center B-cell, and plasma cell differentiation, coupled with lower antibody production. Interestingly, Tregs, including follicular regulatory T (Tfr) cells, were also impaired in the absence of ICOS. Using ICOS conditional knockout specific for Foxp3⁺ cells, we found that ICOS was indispensable for optimal survival and homeostasis of induced Tregs during cGVHD. Furthermore, administration of anti-ICOS alleviated cGVHD severity via suppressing T effector cells without affecting Treg generation. Taken together, ICOS promotes T- and B-cell activation and differentiation, which can promote cGVHD development; however, ICOS is critical for the survival and homeostasis of iTregs, which can suppress cGVHD. Hence, ICOS balances the development of cGVHD and could offer a potential target after allo-HCT in the clinic.

Mesenchymal Stem Cells (MSCs) Attenuate Cutaneous Sclerodermatous Graft-Versus-Host Disease (Scl-GVHD) through Inhibition of Immune Cell Infiltration in a Mouse Model

Human chronic graft-versus-host disease (GVHD) shares clinical characteristics with a murine sclerodermatous GVHD model that is characterized by skin thickening and lung fibrosis. A B10.D2 → BALB/c transplant model of sclerodermatous GVHD was used to address the therapeutic effect of mesenchymal stem cells (MSCs) on the development of chronic GVHD. The clinical and pathological severity of cutaneous sclerodermatous GVHD was significantly attenuated in MSC-treated recipients relative to sclerodermatous GVHD control subjects. After MSC treatment, skin collagen production was significantly reduced, with consistent down-regulation of Tgfb expression. Effects of MSCs on molecular markers implicated in persistent transforming growth factor-β signaling and fibrosis, such as PTEN, phosphorylated Smad-2/3, and matrix metalloproteinase-1, were observed in skin tissue. MSCs neither migrate to the skin nor affect the in vivo expansion of immune effector cells, but they inhibited the infiltration of immune effector cells into skin via down-regulation of CCR4 and CCR8 expression on CD4⁺ T cells and CCR1 on CD11b⁺ monocyte/macrophages. MSCs diminished expression of chemokines such as CCL1, CCL3, CCL8, CCL17, and CCL22 in skin. MSCs were also dependent on stimulated splenocytes to suppress fibroblast proliferation. Our findings indicate that MSCs attenuate the cutaneous sclerodermatous GVHD by selectively blocking immune cell migration and down-regulating chemokines and chemokine receptors.

Effect of roflumilast, novel phosphodiesterase-4 inhibitor, on lung chronic graft-versus-host disease in mice

Chronic graft-versus-host disease (CGVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation. Roflumilast has anti-inflammatory effects and has been used in the treatment of inflammatory airway diseases. It is at present unclear whether roflumilast may have a therapeutic role in CGVHD. To test this, we used the B10.D2 → BALB/c model of CGVHD to address the therapeutic effect of roflumilast on the development of CGVHD. Lungs of animals treated with roflumilast exhibited less chronic inflammatory cell infiltration and fibrosis in the peribronchial and perivascular area versus allogeneic controls. To define the mechanism, we examined the expression of pro-inflammatory and profibrotic cytokines in the lung. Messenger RNA expression of interleukin-6 and interleukin-1β in the lungs was significantly reduced in recipients treated with roflumilast. Similar changes were observed in profibrotic cytokines and chemokines. In addition, the percentage of Foxp3(+) regulatory T cells (Tregs), which have the potential to attenuate GVHD, increased significantly within the CD4(+) T cells with roflumilast in the lungs. In conclusion, roflumilast treatment attenuated murine lung CGVHD by blocking T-cell activation mediated by Tregs and downregulating pro-inflammatory and profibrotic cytokines, resulting in the reduction of lung inflammation and fibrosis.

Differential Effect of MyD88 Signal in Donor T Cells on Graft-versus-Leukemia Effect and Graft-versus-Host Disease after Experimental Allogeneic Stem Cell Transplantation

Despite the presence of toll like receptor (TLR) expression in conventional TCRαβ T cells, the direct role of TLR signaling via myeloid differentiation factor 88 (MyD88) within T lymphocytes on graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) effect after allogeneic stem cell transplantation (allo-SCT) remains unknown. In the allo-SCT model of C57BL/6 (H-2(b)) → B6D2F1 (H-2(b/d)), recipients received transplants of wild type (WT) T-cell-depleted (TCD) bone marrow (BM) and splenic T cells from either WT or MyD88 deficient (MyD88KO) donors. Host-type (H-2(d)) P815 mastocytoma or L1210 leukemia cells were injected either subcutaneously or intravenously to generate a GVHD/GVL model. Allogeneic recipients of MyD88KO T cells demonstrated a greater tumor growth without attenuation of GVHD severity. Moreover, GVHD-induced GVL effect, caused by increasing the conditioning intensity was also not observed in the recipients of MyD88KO T cells. In vitro, the absence of MyD88 in T cells resulted in defective cytolytic activity to tumor targets with reduced ability to produce IFN-γ or granzyme B, which are known to critical for the GVL effect. However, donor T cell expansion with effector and memory T-cell differentiation were more enhanced in GVHD hosts of MyD88KO T cells. Recipients of MyD88KO T cells experienced greater expansion of Foxp3- and IL4-expressing T cells with reduced INF-γ producing T cells in the spleen and tumor-draining lymph nodes early after transplantation. Taken together, these results highlight a differential role for MyD88 deficiency on donor T-cells, with decreased GVL effect without attenuation of the GVHD severity after experimental allo-SCT.

Immunology of hematopoietic stem cell transplant

Hematopoietic stem cell transplantation (HSCT) is a procedure in which infusion of hematopoietic stem cells is used to reestablish hematopoietic function in patients with damaged or defective bone marrow or immune systems. Early and late complications following allogeneic HSCT include acute and chronic graft-versus-host disease (GVHD), donor rejection, graft failure, relapse of primary malignancy, conditioning-related toxicity, immunodeficiency and infections. Immunology has a central role in allogeneic hematopoietic cell transplantation. Any appreciation of the immunological mechanism involved in engraftment, GVHD, the development of tolerance, immune reconstitution, and the control of malignancy requires some understanding of the immunologic basis for immune reactions provoked by grafting tissue from one individual to another. In the future it should be possible to learn what gene(s) must be activated and which must be repressed to force stem cells into division without maturation; to engineer a mechanism into the cells that stops proliferation and sets the stage for amplification; to search if there could be a universal donor cell line, neatly packaged and stabilized in sealed vials and distributed by the pharmaceutical industry; to modify the transplanted cells in such a way that they have a proliferative advantage over those of the host and to deliver the lethal blow against the neoplasm, perhaps the cells that are infused will be engineered in such a way as to be able to distinguish between normal host cells and tumor.

Ibrutinib treatment ameliorates murine chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is a life-threatening impediment to allogeneic hematopoietic stem cell transplantation, and current therapies do not completely prevent and/or treat cGVHD. CD4+ T cells and B cells mediate cGVHD; therefore, targeting these populations may inhibit cGVHD pathogenesis. Ibrutinib is an FDA-approved irreversible inhibitor of Bruton's tyrosine kinase (BTK) and IL-2 inducible T cell kinase (ITK) that targets Th2 cells and B cells and produces durable remissions in B cell malignancies with minimal toxicity. Here, we evaluated whether ibrutinib could reverse established cGVHD in 2 complementary murine models, a model interrogating T cell-driven sclerodermatous cGVHD and an alloantibody-driven multiorgan system cGVHD model that induces bronchiolar obliterans (BO). In the T cell-mediated sclerodermatous cGVHD model, ibrutinib treatment delayed progression, improved survival, and ameliorated clinical and pathological manifestations. In the alloantibody-driven cGVHD model, ibrutinib treatment restored pulmonary function and reduced germinal center reactions and tissue immunoglobulin deposition. Animals lacking BTK and ITK did not develop cGVHD, indicating that these molecules are critical to cGVHD development. Furthermore, ibrutinib treatment reduced activation of T and B cells from patients with active cGVHD. Our data demonstrate that B cells and T cells drive cGVHD and suggest that ibrutinib has potential as a therapeutic agent, warranting consideration for cGVHD clinical trials.

Activation of α7nAChR by nicotine reduced the Th17 response in CD4(+)T lymphocytes

BACKGROUND

nAChRs play an important role in the regulation and modulation of immune cell proliferation, differentiation, migration and cell-cell interactions. The present study was to characterize the expression of α7nAChR on human peripheral blood mononuclear cells (hPBMC) and CD4(+)T lymphocytes, and to explore the change of Th17 expression after activation of α7nAChR on human CD4(+)T lymphocytes.

METHODS

A Ficoll gradient was used to separate hPBMC from whole blood, and then CD4(+)T lymphocytes were isolated by magnetic bead separation. The expression of α7nAChR on PBMC and CD4(+)T lymphocytes was analyzed using flow cytometry before and after stimulation with phytohemagglutinin (PHA). The effect of α7nAChR stimulation by nicotine or inhibition by α-bungarotoxin (α-BTX), as well as Th17 expression on the phenotype of CD4(+)T cells was evaluated using flow cytometric analysis.

RESULTS

The percentage of CD4(+)T cells in reduced PBMC, while the expression of α7nAChR increased when cells were stimulated by nicotine. This effect vanished when co-treated with nicotine and α-BTX. α7nAChR was found to expressed in about 90% of CD4(+)T cells. However, α7nAChR expression reduced to 80% on CD4(+)T cells after stimulation with PHA for 24 h. Stimulation of α7nAChR with nicotine increased the expression of Th17 cells, and this upregulation reduced when AChRα7 was inhibited by α-BTX.

CONCLUSION

α7nAChR was ubiquitously expressed by CD4(+)T lymphocytes, which was correlated with the cell activation status. Meanwhile, activation of nAChRα7 by nicotine in CD4 cells reduced the Th17 response.