Dongchang Zhao

Reciprocal differentiation and tissue-specific pathogenesis of Th1, Th2, and Th17 cells in graft-versus-host disease

In acute graft-versus-host disease (GVHD), naive donor CD4(+) T cells recognize alloantigens on host antigen-presenting cells and differentiate into T helper (Th) subsets (Th1, Th2, and Th17 cells), but the role of Th subsets in GVHD pathogenesis is incompletely characterized. Here we report that, in an MHC-mismatched model of C57BL/6 donor to BALB/c recipient, WT donor CD4(+) T cells predominantly differentiated into Th1 cells and preferentially mediated GVHD tissue damage in gut and liver. However, absence of interferon-gamma (IFN-gamma) in CD4(+) T cells resulted in augmented Th2 and Th17 differentiation and exacerbated tissue damage in lung and skin; absence of both IL-4 and IFN-gamma resulted in augmented Th17 differentiation and preferential, although not exclusive, tissue damage in skin; and absence of both IFN-gamma and IL-17 led to further augmentation of Th2 differentiation and idiopathic pneumonia. The tissue-specific GVHD mediated by Th1, Th2, and Th17 cells was in part associated with their tissue-specific migration mediated by differential expression of chemokine receptors. Furthermore, lack of tissue expression of the IFN-gamma-inducible B7-H1 played a critical role in augmenting the Th2-mediated idiopathic pneumonia. These results indicate donor CD4(+) T cells can reciprocally differentiate into Th1, Th2, and Th17 cells that mediate organ-specific GVHD.

Absence of donor Th17 leads to augmented Th1 differentiation and exacerbated acute graft versus host disease

Th17 is a newly identified T-cell lineage that secretes proinflammatory cytokine IL-17. Th17 cells have been shown to play a critical role in mediating autoimmune diseases such as EAE, colitis, and arthritis, but their role in the pathogenesis of graft-versus-host disease (GVHD) is still unknown. Here we showed that, in an acute GVHD model of C57BL/6 (H-2(b)) donor to BALB/c (H-2(d)) recipient, IL-17(-/-) donor T cells manifested an augmented Th1 differentiation and IFN-gamma production and induced exacerbated acute GVHD. Severe tissue damage mediated by IL-17(-/-) donor T cells was associated with increased Th1 infiltration, up-regulation of chemokine receptors by donor T cells, and enhanced tissue expression of inflammatory chemokines. Administration of recombinant IL-17 and neutralizing IFN-gamma in the recipients given IL-17(-/-) donor cells ameliorated the acute GVHD. Furthermore, the regulation of Th1 differentiation by IL-17 or Th17 may be through its influence on host DCs. Our results indicate that donor Th17 cells can down-regulate Th1 differentiation and ameliorate acute GVHD in allogeneic recipients, and that treatments neutralizing proinflammatory cytokine IL-17 may augment acute GVHD as well as other inflammatory autoimmune diseases.

HDAC inhibitor reduces cytokine storm and facilitates induction of chimerism that reverses lupus in anti-CD3 conditioning regimen.

In allogeneic hematopoietic cell transplantation (HCT), donor T cell-mediated graft versus host leukemia (GVL) and graft versus autoimmune (GVA) activity play critical roles in treatment of hematological malignancies and refractory autoimmune diseases. However, graft versus host disease (GVHD), which sometimes can be fatal, remains a major obstacle in classical HCT, where recipients are conditioned with total body irradiation or high-dose chemotherapy. We previously reported that anti-CD3 conditioning allows donor CD8+ T cells to facilitate engraftment and mediate GVL without causing GVHD. However, the clinical application of this radiation-free and GVHD preventative conditioning regimen is hindered by the cytokine storm syndrome triggered by anti-CD3 and the high-dose donor bone marrow (BM) cells required for induction of chimerism. Histone deacetylase (HDAC) inhibitors such as suberoylanilide hydroxamic acid (SAHA) are known to induce apoptosis of cancer cells and reduce production of proinflammatory cytokines by nonmalignant cells. Here, we report that SAHA inhibits the proliferative and cytotoxic activity of anti-CD3-activated T cells. Administration of low-dose SAHA reduces cytokine production and ameliorates the cytokine storm syndrome triggered by anti-CD3. Conditioning with anti-CD3 and SAHA allows induction of chimerism with lower doses of donor BM cells in old nonautoimmune and autoimmune lupus mice. In addition, conditioning with anti-CD3 and SAHA allows donor CD8+ T cell-mediated GVA activity to reverse lupus glomerulonephritis without causing GVHD. These results indicate that conditioning with anti-CD3 and HDAC inhibitors represent a radiation-free and GVHD-preventative regimen with clinical application potential.

Donor B Cells in Transplants Augment Clonal Expansion and Survival of Pathogenic CD4+ T Cells That Mediate Autoimmune-like Chronic Graft-versus-Host Disease

We reported that both donor CD4+ T and B cells in transplants were required for induction of an autoimmune-like chronic graft-versus-host disease (cGVHD) in a murine model of DBA/2 donor to BALB/c recipient, but mechanisms whereby donor B cells augment cGVHD pathogenesis remain unknown. In this study, we report that, although donor B cells have little impact on acute GVHD severity, they play an important role in augmenting the persistence of tissue damage in the acute and chronic GVHD overlapping target organs (i.e., skin and lung); they also markedly augment damage in a prototypical cGVHD target organ, the salivary gland. During cGVHD pathogenesis, donor B cells are activated by donor CD4+ T cells to upregulate MHC II and costimulatory molecules. Acting as efficient APCs, donor B cells augment donor CD4+ T clonal expansion, autoreactivity, IL-7Rα expression, and survival. These qualitative changes markedly augment donor CD4+ T cells’ capacity in mediating autoimmune-like cGVHD, so that they mediate disease in the absence of donor B cells in secondary recipients. Therefore, a major mechanism whereby donor B cells augment cGVHD is through augmenting the clonal expansion, differentiation, and survival of pathogenic CD4+ T cells.

Anti-CD3 preconditioning separates GVL from GVHD via modulating host dendritic cell and donor T-cell migration in recipients conditioned with TBI

Host dendritic cells (DCs) play a critical role in initiating graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL), and separation of GVL from GVHD remains a major challenge in the treatment of hematologic malignancies by allogeneic hematopoietic cell transplantation (HCT). Here, we show that preconditioning with anti-CD3 monoclonal antibody before conditioning with total body irradiation (TBI) prevents GVHD but retains GVL in a HCT model of major histocompatibility complex (MHC)-mismatched C57BL/6 donor to BALB/c host. Prevention of GVHD is associated with inhibition of donor T-cell expression of homing and chemokine receptors, and inhibition of GVHD target tissue expression of chemokines. Furthermore, inhibition of donor T-cell expression of gut homing alpha4beta7 and chemokine receptor (CCR)9 by anti-CD3 preconditioning results from a reduction of CD103(+) DCs in draining mesenteric lymph nodes (LNs), which is associated with down-regulation of DC expression of CCR7, a receptor required for tissue DC migration to draining LNs. These results indicate that anti-CD3 preconditioning reduces not only tissue release of chemokines but also prevents tissue DC migration to draining LNs and subsequently reduces the capacity of DCs of draining LNs to imprint donor T-cell tissue tropism. Therefore, modulation of host DCs by anti-CD3 preconditioning before HCT represents a new approach for separating GVL from GVHD.

Host APCs Augment In Vivo Expansion of Donor Natural Regulatory T Cells via B7H1/B7.1 in Allogeneic Recipients

Foxp3+ regulatory T (Treg) cells include thymic-derived natural Treg and conventional T-derived adaptive Treg cells. Both are proposed to play important roles in downregulating inflammatory immune responses. However, the mechanisms of Treg expansion in inflammatory environments remain unclear. In this study, we report that, in an autoimmune-like graft-versus-host disease model of DBA/2 (H-2d) donor to BALB/c (H-2d) recipients, donor Treg cells in the recipients predominantly originated from expansion of natural Treg cells and few originated from adaptive Treg cells. In vivo neutralization of IFN-γ resulted in a marked reduction of donor natural Treg expansion and exacerbation of graft-versus-host disease, which was associated with downregulation of host APC expression of B7H1. Furthermore, host APC expression of B7H1 was shown to augment donor Treg survival and expansion. Finally, donor Treg interactions with host APCs via B7.1/B7H1 but not PD-1/B7H1 were demonstrated to be critical in augmenting donor Treg survival and expansion. These studies have revealed a new immune regulation loop consisting of T cell-derived IFN-γ, B7H1 expression by APCs, and B7.1 expression by Treg cells.

Alloimmune Response Results in Expansion of Autoreactive Donor CD4+ T Cells in Transplants That Can Mediate Chronic Graft-versus-Host Disease

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