髓样抑制细胞免疫抑制机理的研究

目的:研究荷瘤小鼠来源的髓样抑制细胞(Myeloid derived suppressor cell,MDSC)在肿瘤免疫抑制中的作用机理。方法:用Percoll分离法从荷瘤小鼠的脾脏和骨髓中分离Gr-1+CD11b+MDSC;用流式细胞术检测MDSC对T细胞增殖的抑制作用;分别用生化法和ELISA技术检测MDSC体外培养上清中抑制性因子NO、ROS和IL-10、TGF-β的含量。结果:MDSC在荷瘤小鼠的脾脏和骨髓中聚集增多,且其在骨髓中所占的比例显著高于脾脏;MDSC可以明显抑制脾脏细胞的增殖,体外培养6小时的MDSC可以分泌大量NO、ROS和IL-10、TGF-β。结论:本实验进一步证实MDSC可以通过分泌大量NO、ROS和IL-10、TGF-β抑制T细胞增殖。     

Neutrophilic myeloid‐derived suppressor cells in cord blood modulate innate and adaptive immune responses

Neonates show an impaired anti‐microbial host defence, but the underlying immune mechanisms are not understood fully. Myeloid‐derived suppressor cells (MDSCs) represent an innate immune cell subset characterized by their capacity to suppress T cell immunity. In this study we demonstrate that a distinct MDSC subset with a neutrophilic/granulocytic phenotype (Gr‐MDSCs) is highly increased in cord blood compared to peripheral blood of children and adults. Functionally, cord blood isolated Gr‐MDSCs suppressed T cell proliferation efficiently as well as T helper type 1 (Th1), Th2 and Th17 cytokine secretion. Beyond T cells, cord blood Gr‐MDSCs controlled natural killer (NK) cell cytotoxicity in a cell contact‐dependent manner. These studies establish neutrophilic Gr‐MDSCs as a novel immunosuppressive cell subset that controls innate (NK) and adaptive (T cell) immune responses in neonates. Increased MDSC activity in cord blood might serve as key fetomaternal immunosuppressive mechanism impairing neonatal host defence. Gr‐MDSCs in cord blood might therefore represent a therapeutic target in neonatal infections.     

Neonatal myeloid derived suppressor cells show reduced apoptosis and immunosuppressive activity upon infection with Escherichia coli

Susceptibility to infection during the neonatal period and reduced control of inflammation in neonates are attributed to immunosuppression persisting from fetal life. Myeloid‐derived suppressor cells (MDSCs) are immature myeloid progenitors with suppressive activity and increased numbers in cord blood. We hypothesized that MDSCs contribute to innate host defence in neonates, paralleled by anti‐inflammatory signalling.Phagocytic activity, infection induced apoptosis, expression of B‐cell lymphoma (Bcl)‐2 family proteins, production of reactive oxygen species (ROS), cytokine production and T‐cell suppression of neonatal granulocytic‐MDSCs (G‐MDSCs) after infection with Escherichia coli (E. coli) were compared to neonatal autologous mature polymorphonuclear leukocytes (PMNs). Phagocytic activity of G‐MDSCs upon infection with E. coli was equal to that of mature PMNs, however, apoptosis of G‐MDSCs was decreased. G‐MDSCs showed enhanced Bcl‐2‐expression and lower ROS production compared to PMNs. Inhibition of Bcl‐2 reduced apoptosis rates of G‐MDSCs to that of mature PMNs. Induction of anti‐inflammatory transforming growth factor beta (TGF‐β) was enhanced, while pro‐inflammatory IL‐8 decreased in G‐MDSCs compared to PMNs. Infected G‐MDSCs strongly suppressed proliferation of T cells. We show a direct role of G‐MDSCs for anti‐bacterial host defence. Prolonged survival and anti‐inflammatory capacity suggest that G‐MDSCs are important for immune‐regulation after bacterial infection.     

Human splenic polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) are strategically located immune regulatory cells in cancer

In contrast to the mouse, functional assets of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) in the human spleen remain to be better elucidated. Here, we report that the spleen in gastric and pancreatic cancer adopts an immune regulatory character, harbors excessive amount of PMN-MDSC, and anatomically enables their interaction with T cells. Compared to the peripheral blood, the spleen from cancer patients contained significantly higher levels of low-density PMN-MDSC, but not early-stage MDSC (e-MDSC) and monocytic-MDSC (M-MDSC). Low-density fraction of polymorphonuclear (PMN) cells was enriched in immature myeloid cells and displayed higher levels of CD10, CD16, and ROS than their blood-derived counterparts. They were also positive for PD-L1, LOX-1, and pSTAT3. The white pulp and periarteriolar lymphoid sheath (PALS) were strategically surrounded by PMN cells that were in contact with T cells. Unlike those from the blood, both low-density and normal-density PMN cells from the human spleen suppressed T cell proliferation and IFN-γ production. Independent of clinical grade, high PMN-MDSC percentages were associated with decreased survival in gastric cancer. In summary, our results outline the immune regulatory role of the spleen in cancer where neutrophils acquire MDSC functions and feasibly interact with T cells.     

Metabolism of L-Arginine by Myeloid-Derived Suppressor Cells in Cancer: Mechanisms of T cell suppression and Therapeutic Perspectives

Patients with cancer have an impaired T cell response that can decrease the potential therapeutic benefit of cancer vaccines and other forms of immunotherapy. The establishment of a chronic inflammatory environment in patients with cancer plays a critical role in the induction of T cell dysfunction. The accumulation of myeloid-derived suppressor cells (MDSC) in tumor bearing hosts is a hallmark of malignancy-associated inflammation and a major mediator of the induction of T cell suppression in cancer. Recent findings in tumor bearing mice and cancer patients indicate that the increased metabolism of L-Arginine (L-Arg) by MDSC producing Arginase I inhibits T cell lymphocyte responses. Here, we discuss some of the most recent concepts of how MDSC expressing Arginase I may regulate T cell function in cancer and suggest possible therapeutic interventions to overcome this inhibitory effect.     

Arginine regulation by myeloid derived suppressor cells and tolerance in cancer: mechanisms and therapeutic perspectives

Summary: Patients with cancer have an impaired T-cell response that can decrease the potential therapeutic benefit of cancer vaccines and other forms of immunotherapy. l -arginine ( l -Arg) is a conditionally essential amino acid that is fundamental for the function of T lymphocytes. Recent findings in tumor-bearing mice and cancer patients indicate that increased metabolism of l -Arg by myeloid derived suppressor cells (MDSCs) producing arginase I inhibits T-lymphocyte responses. Here we discuss some of the most recent concepts how MDSC expressing arginase I may regulate T-cell function in cancer and other chronic inflammatory diseases and suggest possible therapeutic interventions to overcome this inhibitory effect.     

Antigen specificity of immune suppression by myeloid-derived suppressor cells

Among the mechanisms set in motion by the tumor to escape the control of the immune system, MDSCs play a central role in inducing tolerance to a variety of anti-tumor effectors, including T lymphocytes. It has been demonstrated that MDSCs expand in tumor-bearing mice and in cancer patients, leading to an impairment of T cell reactivity against the tumor. However, as the presence of MDSCs is not correlated with a general immune suppression, it was advanced that a mechanism regulating the specificity of MDSC inhibition must be present. In this article, we review the literature showing that MDSCs exert their immune-suppressive function on Ag-specific T cell responses but at times, also on mitogen-activated T lymphocytes, therefore bypassing the Ag dependency. We propose that the features of MDSC-mediated immune suppression might be influenced not only by the specific microenvironment in which MDSCs expand and by the tumor characteristics but also by the levels of activation of the target lymphocytes.     

Myeloid‐derived suppressor cells mediate tolerance induction in autoimmune disease

In multiple sclerosis (MS) T cells aberrantly recognize self‐peptides of the myelin sheath and attack the central nervous system (CNS). Antigen‐specific peptide immunotherapy, which aims to restore tolerance while avoiding the use of non‐specific immunosuppressive drugs, is a promising approach to combat autoimmune disease, but the cellular mechanisms behind successful therapy remain poorly understood. Myeloid‐derived suppressor cells (MDSCs) have been studied intensively in the field of cancer and to a lesser extent in autoimmunity. Because of their suppressive effect on the immune system in cancer, we hypothesized that the development of MDSCs and their interaction with CD4⁺ T cells could be beneficial for antigen‐specific immunotherapy. Hence, changes in the quantity, phenotype and function of MDSCs during tolerance induction in our model of MS were evaluated. We reveal, for the first time, an involvement of a subset of MDSCs, known as polymorphonuclear (PMN)‐MDSCs, in the process of tolerance induction. PMN‐MDSCs were shown to adopt a more suppressive phenotype during peptide immunotherapy and inhibit CD4⁺ T‐cell proliferation in a cell‐contact‐dependent manner, mediated by arginase‐1. Moreover, increased numbers of tolerogenic PMN‐MDSCs, such as observed over the course of peptide immunotherapy, were demonstrated to provide protection from disease in a model of experimental autoimmune encephalomyelitis.     

Regulatory T cells: immune suppression and beyond

Foxp3-expressing regulatory T cells (Tregs) were originally identified as critical in maintaining self-tolerance and immune homeostasis. The immunosuppressive functions of Tregs are widely acknowledged and have been extensively studied. Recent studies have revealed many diverse roles of Tregs in shaping the immune system and the inflammatory response. This review will discuss our efforts as well as the efforts of others towards understanding the multifaceted function of Tregs in immune regulation.     

βhCG mediates immune suppression through upregulation of CD11b+Gr1+ myeloid derived suppressor cells,CD206+ M2 macrophages,and CD4+FOXP3+ regulatory T-cells in BRCA1 deficient breast cancers

BRCA1 mutation is reported in about 70% of all triple negative breast cancers (TNBC), while BRCA1 defect due to promoter hypermethylation is seen in about 30%–60% of sporadic breast cancers. Although PARP inhibitors and platinum-based chemotherapy are used to treat these cancers, more efficient therapeutic approaches are required to overcome the resistance to treatment. Our previous findings have reported elevated βhCG expression but not αhCG in BRCA1 deficient breast cancers. As βhCG causes immune suppression in pregnancy, this study explored the immunomodulatory effect of βhCG in BRCA1mutated/deficient TNBC. We observed that Th1, Th2, and Th17 cytokines are upregulated in the presence of βhCG in BRCA1 defective cancers. In NOD-SCID and syngeneic mouse models, βhCG increases the frequency of Myeloid-derived suppressor cells in tumour tissues and contributes to macrophage reprogramming from antitumor M1 to pro-tumour M2 phenotype. βhCG reduces the CD4⁺T-cell infiltration while increasing the density of CD4⁺CD25⁺FOXP3⁺regulatory T-cell in BRCA1 deficient tumour tissues. In contrast, xenograft tumours with βhCG knocked down TNBC cells did not show these immune suppressive effects. We have also shown that βhCG upregulates pro-tumorigenic markers arginase1(Arg1), inducible nitric oxide synthase, PD-L1/PD-1, and NFκB in BRCA1 defective tumours. Thus, for the first time, this study proves that βhCG suppresses the host antitumor immune response and contributes to tumour progression in BRCA1 deficient tumours. This study will help develop new immunotherapeutic approaches for treating BRCA1 defective TNBC by regulating βhCG.     

Challenges in the pursuit of immune tolerance

Strategies for inducing immune tolerance are fundamentally similar across a spectrum of immune-mediated disorders, including allergic disease, autoimmunity, and rejection of allografts. In each case, the objective of establishing an immunoregulatory balance is challenged by variable upswings in effector cell populations and proinflammatory mediators of immunity, requiring careful, and innovative therapeutic intervention to restore stability. The Immune Tolerance Network, an international consortium sponsored by the National Institutes of Health, seeks to advance both the scientific understanding and the clinical success of immune therapies for these disorders, through an innovative and collaborative effort involving clinical trials and mechanistic studies. Over the last decade, scientists have evaluated cell-based ablation and deviation strategies in trials using lymphocyte-specific targeting, induction of host-donor hematopoietic chimerism, induction of antigen-specific immune regulation, and a variety of antigen desensitization approaches. In this article, we review some of the highlights of this experience and discuss the potential for progress, utilizing new insights into regulatory mechanisms and biomarker signatures of tolerance.     

浆细胞样树突状细胞与免疫耐受

浆细胞样树突状细胞(PDC)来源于淋巴系干细胞,其表面标志、功能有别于髓系DC,不仅在抗病毒免疫中发挥重要作用,而且通过多种途径诱导T细胞失能和调节性T细胞的形成,从而参与免疫耐受的诱导.PDC诱导T细胞免疫耐受的分子机制与吲哚胺2,3-双加氧酶(IDO)-色氨酸代谢通路和具有抑制功能的膜分子密切相关.深入阐明PDC诱导耐受的机制,将为免疫耐受异常相关的疾病的治疗提供新方案.     

髓系来源抑制细胞促进肿瘤免疫逃逸的研究进展

髓系来源抑制细胞(MDSC)是髓系来源的一群异质细胞,在荷瘤小鼠模型及肿瘤患者均发挥免疫抑制作用.肿瘤MDSC免疫逃逸作用的机制目前已取得了很多进展,这群细胞可以通过上调精氨酸酶1(ARN1),诱导一氧化氮合酶(iNOS or NOS-2)表达,增加一氧化氮(NO)、活化氧自由基(ROS)等的释放,分解肿瘤微环境中的半...     

Selective suppression of antigen-specific Th2 cells by continuous micro-dose oral tolerance

The effect on antigen (Ag)-specific Th2 response as well as IgE production of continuous oral administration of micro-doses of Ag was investigated. Transgenic (Tg) mice carrying the α β-T cell receptor (TCR) genes specific for ovalbumin (OVA) peptide fragment 323 – 339 were continuously fed with micro-doses of OVA (100 μg/day) for 14 days. Mice were first immunized by OVA in alum and pertussis toxin 7 days before the oral feeding and given a second immunization 1 day after the oral treatment. This feeding regimen tolerized Th2 but not Th1 responses as shown by decrease of Ag-driven cell proliferation and cytokine secretion of IL- 4 but not of IL-2 or IFN-γ as well as by the absence of Ag-specific antibody production of IgE and IgG1, but not of IgG2a or total IgG. Numbers of clonotype-specific TCR-high CD4-positive T cells in peripheral lymphoid tissues markedly decreased in the orally treated group but not in the control group. However, total numbers of CD4-positive T cells in thymus, spleen and lymph nodes were not affected by the oral treatment, indicating that tolerance induction in Th2 cells was mainly due to the down-regulation of TCR and not clonal deletion. The population of antigen-presenting cells expressing B7-2 (CD86) Ag on the surface was decreased in the spleen of the mice which underwent the feeding regimen. The present results suggest that Ag-specific low responsiveness in Th2 cells, which resulted in suppres sion of the Ag-specific IgE production, can be achieved by continuous feeding with microdoses of Ag.     

肝窦状内皮细胞(LSECs)与肝脏免疫耐受

肝脏是机体重要的免疫器官,其解剖部位和功能特性决定了肝脏具有独特的免疫机制。一方面需要强大的免疫应答能力抗感染,另一方面需要强有力的调节机制避免不必要的免疫激活,而后者主要通过免疫耐受来实现。在肝脏的免疫防御系统中,肝窦状内皮细胞通过抗原特异性的免疫耐受诱导以及T淋巴细胞的凋亡诱导与清除,从而在肝脏的局部免疫以及全身免疫调控、器官移植耐受以及病毒感染的慢性化等生理病理过程中发挥着关键作用。     

Polyunsaturated fatty acids promote the expansion of myeloid‐derived suppressor cells by activating the JAK/STAT3 pathway

Polyunsaturated fatty acids (PUFAs) exert immunosuppressive effects that could prove beneficial in clinical therapies for certain autoimmune and inflammatory disorders. However, the mechanism of PUFA‐mediated immunosuppression is far from understood. Here, we provide evidence that PUFAs enhance the accumulation of myeloid‐derived suppressor cells (MDSCs), a negative immune regulator. PUFA‐induced MDSCs have a more potent suppressive effect on T‐cell responses than do control MDSCs. These observations were found both in cultured mouse bone marrow cells in vitro and in vivo in mice fed diets enriched in PUFAs. The enhanced suppressive activity of MDSCs by PUFAs administration was coupled with a dramatic induction of nicotinamide adenine dinucleo‐ tide phosphate oxidase subunit p47^phox and was dependent on reactive oxygen species (ROS) production. Mechanistic studies revealed that PUFAs mediate its effects through JAK‐STAT3 signaling. Inhibition of STAT3 phosphorylation by JAK inhibitor JSI‐124 almost completely abrogated the effects of PUFAs on MDSCs. Moreover, the effects of PUFAs on MDSCs and the underlying mechanisms were confirmed in tumor‐bearing mice. In summary, this study sheds new light on the immune modulatory role of PUFAs, and demonstrates that MDSCs expansion may mediate the effects of PUFAs on the immune system.     

HLA-G与免疫耐受

HLA-G是一种非经典人类主要组织相容性复合物Ⅰ类分子,与器官移植、生殖及肿瘤等多种免疫反应有关,是引起免疫耐受的一种因子.     

人肝癌HepG2细胞小鼠荷瘤模型的建立及免疫耐受的探讨

目的 建立正常免疫背景小鼠的人肝癌荷瘤模型,探讨人肿瘤细胞与胎鼠异种嵌合产生的免疫耐受。 方法 用绿色荧光蛋白（GFP）标记人肝癌细胞系HepG2,将GFP- HepG2细胞注射入孕16.5d的胎鼠腹腔内,观察新生小鼠腹腔内荷瘤情况及酶联免疫吸附法（ELISA）检测荷瘤小鼠血清人甲胎蛋白（AFP）含量; 小鼠成年后进行皮下成瘤实验及流式细胞术检测小鼠脾脏Ｔ淋巴细胞亚群变化。 结果 观察到经胎鼠腹腔注射的人GFP- HepG2细胞在新生鼠体内种植并生长于肝脏,分泌人甲胎蛋白;皮下荷瘤实验观察到经胎体注射GFP HepG2细胞诱导免疫耐受后,部分小鼠成年后仍可支持皮下HepG2细胞荷瘤,流式细胞术检测表明,诱导耐受后的小鼠免疫系统仍对人肝癌细胞保留有较弱的攻击。 结论 通过胎鼠腹腔注射人GFP- HepG2细胞可以建立人肝癌细胞小鼠荷瘤模型,部分荷瘤后的小鼠具有免疫耐受的能力。