Cytotoxic T Lymphocyte Antigen-4 Down-Regulates T Helper 1 Cells by Increasing Expression of Signal Transducer and Activator of Transcription 3 in Acute Graft-versus-Host Disease

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.

Immune Checkpoints and targeted agents in relapse and graft-versus-host disease after hematopoietic stem cell transplantation

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for malignant hematologic disorders. Novel anti-infection agents have successfully decreased the risk of fatal infections post-HSCT in recent years, but the relapse of primary disease and graft-versus-host disease (GVHD) remain the major causes of death for transplant recipients, and significantly deteriorate the quality of life. Thus, it is crucial to maintain the immune homeostasis in transplant recipients and balance the graft-versus-leukemia (GVL) effect and GVHD.

METHODS

We reviewed the recently published literatures on immune checkpoint (IC) and targeted agents in relapse and GVHD after allogeneic HSCT RESULTS: Emerging data suggest that IC is an attractive target to modulate immune responses, and accumulating evidences of IC-targeted agents have been published for the treatment of malignancies and autoimmune disorders. The unique mechanism of IC-targeted agents, which affects the immune homeostasis of the transplant recipient by modulating alloreactivity, minimizes the risk of organ toxicity and immunosuppression associated with conventional therapy CONCLUSION: There is an increase in literature reporting the application of immune checkpoint-targeted agents in HSCT settings, and an overview will benefit further exploration in this field.

Case report: Challenges in immune reconstitution following hematopoietic stem cell transplantation for CTLA-4 insufficiency-like primary immune regulatory disorders

Cytotoxic T-lymphocyte antigen-4 (CTLA-4) haploinsufficiency is a T-cell hyperactivation disorder that can manifest with both immunodeficiency and immune dysregulation. Approximately one-third of patients may present mild symptoms and remain stable under supportive care. The remaining patients may develop severe multiorgan autoimmunity requiring lifelong immunosuppressive treatment. Hematopoietic stem cell transplantation (HSCT) is potentially curable for patients with treatment-resistant immune dysregulation. Nevertheless, little experience is reported regarding the management of complications post-HSCT. We present case 1 (CTLA-4 haploinsufficiency) and case 2 (CTLA-4 insufficiency-like phenotype) manifesting with severe autoimmunity including cytopenia and involvement of the central nervous system (CNS), lung, and gut and variable impairment of humoral responses. Both patients underwent HSCT for which the main complications were persistent mixed chimerism, infections, and immune-mediated complications [graft-versus-host disease (GVHD) and nodular lung disease]. Detailed management and outcomes of therapeutic interventions post-HSCT are discussed. Concretely, post-HSCT abatacept and human leukocyte antigen (HLA)-matched sibling donor lymphocyte infusions may be used to increase T-cell donor chimerism with the aim of correcting the immune phenotype of CTLA-4 haploinsufficiency.

Role of T cell immune response cDNA 7 on the pathology of acute graft-versus-host disease

Activation of T lymphocytes is the initiating factor of the occurrence of acute graft-versus-host disease (aGVHD), and cytotoxic T lymphocyte antigen-4 (CTLA-4) is the inhibitory receptor for activating T cells. T cell immune response cDNA 7 (TIRC7) is considered an upstream regulator of CTLA-4; however, little is understood regarding the effects of TIRC7 on the regulation of CTLA-4 in aGVHD. The purpose of the present study was to evaluate the regulatory effects of TIRC7 on aGVHD, mainly in the pathology. Recipient mice were exposed to a preconditioning dose of 7.5 Gy irradiation on the day of the transplantation and were divided into the following groups: Blank control group, bone marrow transplantation control group, total body irradiation group, mild-moderate aGVHD group and severe aGVHD group. According to the different administration of CTLA-4 and TIRC7 monoclonal antibodies, the mild-moderate and severe aGVHD groups were randomly divided into the hematopoietic stem cell transplantation (HSCT) and HSCT + CTLA-4/TIRC7 groups. Recipient mice were sacrificed at different time points post-HSCT for histopathological analysis by hematoxylin and eosin staining. Compared with the control and other experimental groups, the mice in the combined CTLA-4 and TIRC7 group exhibited ameliorated pathological injury, and lower pathology scores of the liver, lung and intestine. These data revealed that intraperitoneal injection of anti-TIRC7 and/or anti-CTLA-4 monoclonal antibody into mice could effectively alleviate the severity of aGVHD.

TIRC7 inhibits Th1 cells by upregulating the expression of CTLA‑4 and STAT3 in mice with acute graft‑versus‑host disease

In a previous study, it was demonstrated that T‑cell immune response cDNA 7 (TIRC7) levels reflect the efficacy of treatment of patients with acute graft‑versus‑host disease (GVHD). However, the pathogenesis of TIRC7 in acute GVHD remains poorly understood. Lymphocytes from patients with acute GVHD were selected as targeT cells, and the effects of TIRC7 on cytotoxic T lymphocyte antigen‑4 (CTLA‑4), T cell activation and cytokine secretion were observed by electroporation. A mouse model of acute GVHD was established; anti‑TIRC7 and anti‑CTLA‑4 monoclonal antibodies were intraperitoneally injected into recipient mice. Then, the effects of TIRC7 and CTLA‑4 on T cell activation and acute GVHD were monitored. After TIRC7 expression was downregulated, CTLA‑4 levels were decreased and STAT3 phosphorylation was reduced; conversely, the activation capacity of T lymphocytes was elevated, and the secretion of interferon‑γ and other cytokines was increased. The mice in the TIRC7 + CTLA‑4 co‑administration group exhibited the lowest acute GVHD scores, with the longest average survival time and shortest recovery time of hematopoietic reconstitution. In conclusion, the results indicated that TIRC7 may positively regulate the function of CTLA‑4 and inhibit T cell activation, thus suppressing the development and progression of acute GVHD.

STAT3 Expression in Host Myeloid Cells Controls Graft-versus-Host Disease Severity

Professional antigen-presenting cells (APCs) are important modulators of acute graft-versus-host disease (GVHD). Although dendritic cells (DCs) are the most potent APC subset, other myeloid cells, especially macrophages (MFs) and neutrophils, recently have been shown to play a role in the severity of GVHD. The critical molecular mechanisms that determine the functions of myeloid cells in GVHD are unclear, however. Signal transducer and activator of transcription 3 (STAT3) is a master transcription factor that plays a crucial role in regulating immunity, but its role in MF biology and in acute GVHD remains unknown. To determine the impact of myeloid cell-specific expression of STAT3 on the severity of acute GVHD, we used myeloid cell-specific STAT3-deficient LysM-Cre/STAT3^fl/- animals as recipients and donors in well-characterized experimental models of acute GVHD. We found that reduced expression of STAT3 in myeloid cells from the hosts, but not the donors, increased inflammation, increased donor T cell activation, and exacerbated GVHD. Our data demonstrate that STAT3 in host myeloid cells, such as MFs, dampens acute GVHD.