B7-H1/PD-1共刺激途径对慢性乙型肝炎患者HBV特异性T淋巴细胞功能的影响

目的研究B7-H1／PD-1共刺激信号途径对慢性乙型肝炎（chronic hepatitis B，CHB）患者HBV特异性T淋巴细胞免疫功能的影响。方法流式细胞术检测CHB患者和健康人外周血髓样树突细胞（myeloid dendritic cells，mDC）上B7-H1及T淋巴细胞上PD-1的表达水平，并分析患者B7-H1和PD-1的表达水平与ALT水平的相关性；体外培养CHB患者单核细胞来源的树突细胞（monocyte-derived cells，MoDC），HBcAg负载后用“细胞因子鸡尾酒”（TNF-α、IL-6、IL-1β和PGE2）促成熟。MoDC和自体T淋巴细胞混合培养，并对B7-H1／PD-1途径进行阻断处理，^3H-TdR掺入法检测HBV特异性T淋巴细胞增殖的能力；ELISA法检测混合淋巴细胞培养上清中细胞因子的浓度；ELISPOT法检测分泌IFN-γ的T淋巴细胞频数。结果B7-H1及受体PD-1在CHB患者外周血mDC和T淋巴细胞上的表达水平明显升高，且B7-H1和PD-1的表达水平与患者的ALT水平呈明显的正相关；阻断B7-H1／PD-1共刺激途径，不但能够促进HBV特异性T淋巴细胞的增殖和Ⅰ型细胞因子分泌，同时可以提高分泌IFN-γ的抗原特异性T淋巴细胞的频数。结论CHB患者B7-H1和PD-1表达水平的升高，降低了HBV特异性T淋巴细胞免疫功能。     

B7-H1共刺激信号途径及其病理作用机制研究进展

B7-H1首先是在与B7-1/B7-2的同源性分析中发现的。可在多数外周和造血组织中诱导表达。通过与na ve T细胞上未定受体结合,B7-H1共刺激T细胞增殖并诱导IL-10和IFN-γ生成。B7-H1的共刺激作用对淋巴器官T细胞的成熟和分化有重要作用。相反,通过结合活化T细胞和B细胞上的PD-1受体,B7-H1诱导凋亡和延滞细胞周期而抑制T细胞反应。在癌症、类风湿、HIV感染等疾病中发现B7-H1有负调节作用。对B7-H1路径进行调控有助于自身免疫病及恶性肿瘤的治疗。     

B7-1/B7-H1相对比例变化对Hsp70-肽复合物抗肿瘤免疫效应的影响

目的：探讨Hsp7肽复合物对B7-1／B7-H1相对比例的影响及真核表达可溶性PD-1(sPD-1)对Hsp70-肽复合物抗肿瘤作用的影响。方法：通过RT-PCR和半定量PCR技术检测Hsp70-肽复合物体外刺激和体内免疫对小鼠脾细胞正调控共刺激分子B7-1和抑制性共刺激分子B7-H1及其受体PD-1表达的影响；体内转染表达sPD-1后，观察Hsp70-肽复合物免疫小鼠的肿瘤生长以及脾淋巴细胞毒性的变化。结果：基因表达检测表明．Hsp70-肽复合物体外刺激的小鼠脾细胞B7-1 mRNA和B7-H1 mRNA的水平随时问而变化，B7-1／B7-H1比值随刺激时间而增高；Hsp70-肽复合物体内免疫小鼠后期脾细胞B7-1表达下降，B7-H1及其受体PD-1表达上调，B7-1／B7-H1比值逆转；体内表达sPD-1可显著增强和延长Hsp70-肽复合物的抑瘤效果；体内表达sPD-1可提高Hsp70-肽复合物免疫的荷瘤小鼠脾细胞的杀伤率。结论：Hsp70-肽复合物的刺激引起共刺激分子B7-1和B7-H1表达的变化，B7-1／B7-H1的比例与激活效应相关，sPD-1通过阻抑B7-H1／PD-1途径、上调B7-1／B7-H1比例，可增强免疫应答，提高Hsp70-肽复合物特异性免疫治疗肿瘤的效应。     

PD-1/PD-L1抑制性通路在病毒性感染中的研究进展

杀伤性T细胞(CTL)是病毒感染过程中主要的效应细胞.在急性病毒性感染中,CTL细胞通过杀伤病毒感染的细胞,分泌抗病毒细胞因子从而有效清除病毒.而在慢性病毒感染过程中,病毒特异性CTL发生克隆耗竭,细胞数量少,细胞功能受损,分泌细胞因子能力下降.目前证明,CD28家族成员Programmed Death-1(PD-1)是一种重要的细胞表面分子,能够抑制CTL细胞功能,参与外周免疫耐受,维持T细胞克隆耗竭,保护机体不受免疫病理损伤.在慢性病毒性感染中,T细胞表面的PD-1与其受体PD-L1/2结合后,传递抑制性信号,下调外周T细胞功能.阻断PD-1通路,能够重建CD8+T细胞功能,抑制病毒复制,促进病毒清除.因此,通过干扰PD-1/PD-L1抑制途径进行免疫调节,可能是处理慢性病毒感染性疾病的一个新方法.     

B7-H1共刺激信号途径及其病理作用机制研究进展

B7-H1首先是在与B7-1／B7-2的同源性分析中发现的。可在多数外周和造血组织中诱导表达。通过与naive T细胞上未定受体结合，B7-H1共刺激T细胞增殖并诱导IL-10和IFN-γ生成。B7-H1的共刺激作用对淋巴器官T细胞的成熟和分化有重要作用。相反，通过结合活化T细胞和B细胞上的PD-1受体，B7-H1诱导凋亡和延滞细胞周期而抑制T细胞反应。在癌症、类风湿、HIV感染等疾病中发现B7-H1有负调节作用。对B7-H1路径进行调控有助于自身免疫病及恶性肿瘤的治疗。     

PD-1/PD-L信号通路研究进展

PD-1是近年新发现的一个负性共刺激信号分子,其配体为PD-L1和PD-L2,共属于CD28/B7家族。PD-1/PD-L通路削弱、限制和/或终止T细胞、B细胞和骨髓细胞的活化及外周炎症的效应器功能;二者相互作用导致T细胞增殖抑制和细胞因子IL-2I、L-10和IFN-γ的分泌下降,在移植免疫、自身免疫及肿瘤免疫等体系中发挥着重要作用。     

PD-1及PD-L1与肿瘤适应性免疫抵抗的研究进展

程序性死亡蛋白-1(programmed death protein 1,PD-1)与其配体程序性死亡配体1(programmed cell death-ligand 1,PD-L1)属于CD28/B7家族,是近年研究比较透彻的免疫检查点分子。PD-1/PD-L1通过调节外周组织中免疫反应的持续性和效价避免组织损伤并维持对于自身抗原的耐受。肿瘤细胞主动性抑制T细胞的机制称为适应性免疫抵抗(adaptive immune resistance),即肿瘤抗原特异性T细胞企图攻击肿瘤,但肿瘤细胞发生反应性改变(诱导表达PD-L1)从而避免免疫攻击。适应性免疫抵抗过程中的关键分子即为PD-1/PD-L1。PD-1/PD-L1抗体治疗已在临床试验中显示出良好的疗效,使阻断适应性免疫抵抗有望成为重要的肿瘤免疫治疗手段。分析肿瘤活检样本的基线免疫信息能指导制定个体化的免疫治疗方案。本文就PD-1/PD-L1的生物学结构、适应性免疫抵抗机制及相关临床决策等进行综述。     

B/T淋巴细胞间抑制信号研究进展

B7-CD28家族共刺激信号分子在T淋巴细胞激活、抑制机体耐受及产生理想的T细胞免疫应答等方面起着关键作用。B7-CD28家族共信号分子已经被集中的研究,并且引起免疫调控领域充分的重视。CD80/CD86/CD28/CTLA-4经典途径的新功能的发现以及这一家族包括B7-H1/B7-DC/PD-1,B7-H2/ICOS,B7-H4和BTLA的新途径的确定,都拓宽了我们对T细胞介导的免疫应答和免疫耐受调控的理解。本文就CTLA-4、PD-1和BTLA对T细胞应答的负性调节以及在维持外周耐受中起作用的研究进展作一综述。     

B／T淋巴细胞问抑制信号研究进展

B7-CD28家族共刺激信号分子在T淋巴细胞激活、抑制机体耐受及产生理想的T细胞免疫应答等方面起着关键作用。B7-CD28家族共信号分子已经被集中的研究，并且引起免疫调控领域充分的重视。CD80/CD86，CD28/CTLA-4经典途径的新功能的发现以及这一家族包括B7-H1／B7-DC／PD-1，B7-H2／ICOS，B7-H4和BTLA的新途径的确定，都拓宽了我们对T细胞介导的免疫应答和免疫耐受调控的理解。本就CTLA-4、PD-1和BTLA对T细胞应答的负性调节以及在维持外周耐受中起作用的研究进展作一综述。     

PD-1／PD-L信号通路研究进展

PD-1是近年新发现的一个负性共刺激信号分子，其配体为PD-L1和PD-L2，共属于CD28／B7家族。PD-1／PD-L通路削弱、限制和／或终止T细胞、B细胞和骨髓细胞的活化及外周炎症的效应器功能；二者相互作用导致T细胞增殖抑制和细胞因子IL-2、IL-10和IFN-γ的分泌下降，在移植免疫、自身免疫及肿瘤免疫等体系中发挥着重要作用。     

Increased B7-H1 Expression on Peripheral Blood T Cells in Oral Lichen Planus Correlated with Disease Severity

Background

Oral lichen planus (OLP) is a chronic and T cell-mediated autoimmune disease whose immunopathogenesis may involve antigen-presentation, T cells activation and migration as well as keratinocytes apoptosis. PD-1/B7-H1 pathway may have a unique function in regulating self-reactive T cells associated with inflammatory response and maintaining tolerance in peripheral tissues. In this study, we aimed to explore the contribution of PD-1/B7-H1 pathway to OLP.

Methods

We determined the expression of PD-1 and B7-H1 on peripheral blood T cells from OLP cases and analyzed their association with disease severity assessed by RAE (reticular, atrophic and erosive lesion) scoring system. In addition, interferon-γ, interleukin (IL)-2, IL-4, IL-10 and soluble PD-1 concentrations in serum were measured using ELISA. Then, we explored the regulation of PD-1/B7-H1 pathway on T cells immune response in OLP by blockade of PD-1 or B7-H1.

Results

We found that PD-1 and B7-H1 were up-regulated on peripheral blood T cells from OLP patients and B7-H1 expression positively correlated with disease severity of OLP. It is suggested that Th1 dominant inflammatory situation might contribute to the high expression of PD-1 and B7-H1 in OLP. Blockade of PD-1/B7-H1 pathway significantly increased the proliferation, and IFN-γ and IL-2 production of T cells.

Conclusions

PD-1/B7-H1 pathway may play an important role in negatively modulating T cell-mediated immune response in OLP, and provide the rationale to employ B7-H1 expression on peripheral blood T cells as a marker of severity of OLP and to develop agonists targeting PD-1/B7-H1 pathway as a promising immunotherapeutic strategy for OLP.     

B7-H1 up-regulation impairs myeloid DC and correlates with disease progression in chronic HIV-1 infection

Impaired myeloid dendritic cells (mDC) fail to elicit host antiviral immune responses, leading to disease progression in HIV-1 infection. However, mechanisms underlying mDC suppression remain elusive. In this study, we found that the T-cell co-stimulatory molecule programmed death-1 ligand-1 (B7-H1) is significantly up-regulated on peripheral mDC in HIV-1-infected typical progressors and AIDS patients, but is maintained at a relatively low level in long-term non-progressors. Successful immune reconstitution after highly active antiretroviral therapy, indicated by full suppression of HIV-1 replication and substantial increases of CD4 T-cell counts, correlated with a decrease in B7-H1 expression. Importantly, we also found that X4 HIV-1 isolates directly induced B7-H1 expression on mDC in vitro, while adding antiviral agents hampered this B7-H1 up-regulation. Blockade of B7-H1 in vitro strongly enhanced mDC-mediated allostimulatory capacity and IL-12 production. In contrast, B7-H1 ligation with soluble programmed death-1 (PD-1) reduced mDC maturation and IL-12 production but increased mDC apoptosis and IL-10 production. Thus, B7-H1 up-regulation may inhibit mDC-mediated immune response, thereby facilitating viral persistence and disease progression in HIV-1-infected patients. This study provides new evidence that B7-H1 inhibitory signaling may reversely mediate functional impairment of mDC in HIV-1 infection, which further supports the notion that B7-H1 blockade represents a novel therapeutic approach to this disease.     

Co-inhibitory role of T-cell-associated B7-H1 and B7-DC in the T-cell immune response

B7-H1 and B7-DC expressed on antigen-presenting cells inhibit the T-cell response via the PD-1 counter-receptor on T cells, and co-stimulate T-cell immunity under certain conditions via an unidentified co-stimulatory receptor. However, little is known about the functional consequence of T-cell-associated B7-H1 or B7-DC in the T-cell immune response. Therefore, we evaluated the physiological role of B7-H1 and B7-DC expressed on T cells in terms of cell proliferation and cytokine production by alloreactive T cells. We found that PD-1, B7-H1, and B7-DC were up-regulated in alloreactive CD4(+) and CD8(+) T cells in vitro and in vivo. In the alloreactive T-T model, blockade of the B7-H1:PD-1 or B7-DC:PD-1 pathways significantly increased the proliferation, and IFN-gamma and IL-2 production of alloreactive T cells, although it did not affect the production of other cytokines, including IL-4, IL-10, and IL-12. The data indicate that T-cell-associated B7-H1 and B7-DC negatively regulate the T-cell response via the T-T interaction.     

Unique B7-H1 expression on masticatory mucosae in the oral cavity and trans-coinhibition by B7-H1-expressing keratinocytes regulating CD4+ T cell-mediated mucosal tissue inflammation

The PD-1/B7-H1 pathway regulates immune responses and maintains homeostasis. Here, we identified a unique expression of B7 homolog 1 (B7-H1) on masticatory mucosae in the oral cavity. B7-H1 was physiologically expressed on the dorsal surface of the tongue, gingiva, and hard palate. Other squamous epithelia and other structures of the epithelia did not express B7-H1 in the steady state. Physiological B7-H1 expression on masticatory mucosae was limited on prickle cells, and its expression on basal keratinocytes (KCs) was strictly regulated. B7-H1 on prickle cells was upregulated by external topical stimuli, but B7-H1 on basal KCs was induced only by internal stimuli via infiltrating cells. The blocking of KC-associated B7-H1 or the lack of programmed cell death-1 (PD-1) on tissue effector CD4⁺ T cells in mice lacking B7-H1 on immune cells drastically exacerbated the tissue inflammation induced by topical OVA painting as an exogenous antigen, indicating direct interaction with KCs and CD4⁺ T cells. Trans-coinhibitory signals by KCs may modulate local T-cell/dendritic cell activation, resulting in inhibition of T-cell responses in both peripheral and secondary lymphoid tissues. Careful control of B7-H1 induction in KCs may play a crucial role in the protection from CD4⁺ T cell-mediated tissue inflammation by exogenous antigens delivered from the mucosal surface.     

Preferential contribution of B7-H1 to programmed death-1-mediated regulation of hapten-specific allergic inflammatory responses

Programmed death-1 (PD-1) and its ligands, B7-H1/PD-L1 and B7-DC/PD-L2, are new CD28-B7 family members that may be involved in the regulation of immune responses. We examined the roles of these molecules in mouse hapten-induced contact hypersensitivity (CH). Administration of anti-PD-1 mAb at sensitization significantly enhanced and prolonged ear swelling. Treatment with anti-B7-H1 mAb, but not anti-B7-DC mAb, also enhanced CH reactions. The anti-PD-1 mAb treatment at sensitization significantly increased the T cell number of draining lymph nodes (DLN). B7-H1 was induced on activated T cells and antigen-presenting cells (APC) in the skin and the DLN, whereas B7-DC expression was restricted to dendritic cells (DC) in the dermis and the DLN. A particular subset of DC, B7-H1(+)B7-DC(-)CD86(low), was found in sensitized DLN. The blockade of B7-H1, but not B7-DC, dramatically enhanced the initial T cell proliferative responses against hapten-pulsed DLN APC, suggesting the preferential contribution of B7-H1 to the T cell-APC interaction. Our results demonstrate the regulatory role of PD-1 and the differential roles of B7-H1 and B7-DC in hapten-induced immune responses. The PD-1-B7-H1 pathway may play a unique role in regulating inflammatory responses.     

Intrahepatic PD-1/PD-L1 Up-regulation Closely Correlates with Inflammation and Virus Replication in Patients with Chronic HBV Infection

Chronic hepatitis B was characterized by fluctuant immune response to infected hepatocytes resulting in hepatic inflammation and virus persistence. Recently, Programmed Death-1 (PD-1) and its ligand PD-L1 have been demonstrated to play an essential role in balancing antiviral immunity and inflammation in the livers of acute hepatitis B patients, significantly influencing disease outcome. PD-1 up-regulation in peripheral T cells is associated with immune dysfunction in chronic hepatitis B patients. However, the effect of PD-1/PD-L1 on hepatic damage and chronic infective status is still unknown in patients with chronic HBV infection. Here, we report up-regulation of PD-1 and PD-L1 in liver biopsies from 32 chronic HBV patients compared to 4 healthy donors. PD-1/PD-L1 up-regulation was significantly associated with hepatic inflammation and ALT elevation. Moreover, appropriate up-regulation but not overexpression of PD-L1 in the active phase of chronic hepatitis B as well as lower expression of PD-L1 in the inactive phase in liver residential antigen presenting cells (including Kupffer cells and sinusoidal endothelial cells) may contribute to viral inhibition. Our data suggest that the intrahepatic interaction of PD-1 and PD-L1 might play an important role in balancing the immune response to HBV and immune-mediated liver damage in chronic HBV infection.     

The B7-H4 gene induces immune escape partly via upregulating the PD-1/Stat3 pathway in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is associated with high mortality rates worldwide. The costimulatory molecule, B7-H4, a member of the B7 family, plays an important role in immune regulation, mainly by inhibiting the proliferation of T cells to achieve a negative regulatory T cell immune response. The mechanism of action of B7-H4 in non-small cell lung cancer is unknown at present. Tumor tissues from 71 patients subjected to radical pneumonectomy were examined, along with NSCLC cells and BALB/c mice. Among the 71 NSCLC cases, overall and recurrence-free survival rates were significantly lower in those displaying high B7-H4 expression. Mechanistic analyses showed that B7-H4 promoted the growth and metastasis of non-small cell lung cancer tumor tissues in mice through effects on CD8⁺ T cell apoptosis. Data from western blot experiments further suggested that B7-H4 induced CD8⁺ T cell death, both in vitro and in vivo, and affecting the PD-1/Stat3 pathway and promoting immune escape of tumor cells. Our collective findings support the potential utility of B7-H4 gene expression as a marker of NSCLC prognosis and provide a novel strategy for targeted therapy.     

Emerging concepts in PD-1 checkpoint biology

The PD-1 pathway is a cornerstone in immune regulation. While the PD-1 pathway has received considerable attention for its role in contributing to the maintenance of T cell exhaustion in chronic infection and cancer, the PD-1 pathway plays diverse roles in regulating host immunity beyond T cell exhaustion. Here, we discuss emerging concepts in the PD-1 pathway, including (1) the impact of PD-1 inhibitors on diverse T cell differentiation states including effector and memory T cell development during acute infection, as well as T cell exhaustion during chronic infection and cancer, (2) the role of PD-1 in regulating Treg cells, NK cells, and ILCs, and (3) the functions of PD-L1/B7-1 and PD-L2/RGMb/neogenin interactions. We then discuss the emerging use of neoadjuvant PD-1 blockade in the treatment of early-stage cancers and how the timing of PD-1 blockade may improve clinical outcomes. The diverse binding partners of PD-1 and its associated ligands, broad expression patterns of the receptors and ligands, differential impact of PD-1 modulation on cells depending on location and state of differentiation, and timing of PD-1 blockade add additional layers of complexity to the PD-1 pathway, and are important considerations for improving the efficacy and safety of PD-1 pathway therapeutics.     

Intrahepatic expression of the co-stimulatory molecules programmed death-1, and its ligands in autoimmune liver disease

Liver-infiltrating T cells play an essential role in the immunopathogenesis of autoimmune liver disease. Programmed death-1 (PD-1) and its ligands, B7-H1/PD-L1 and B7-DC/PD-L2, are new CD28-B7 family members that are involved in the regulation of immune responses. The ligation of PD-1 inhibits T-cell receptor-mediated T cell proliferation and cytokine production, and PD-1-deficient mice develop various organ-specific autoimmune diseases. To investigate the expressions of PD-1 and its ligands in autoimmune liver disease, in particular autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC), immunohistochemical analysis was performed. Liver biopsy specimens obtained from 17 patients with AIH and PBC were studied. PD-1 was expressed on more than half of the liver-infiltrating T cells within the portal tract. Some of the intrahepatic T cells expressed B7-H1 in patients with AIH and PBC. B7-H1 and B7-DC were mainly expressed on some Kupffer cells (KC) and liver sinusoidal endothelial cells (LSEC) within the sinusoids and their expression was upregulated in autoimmune liver disease. These results suggest that the interaction of PD-1 on T cells with increased expression of B7-H1 and B7-DC on KC and LSEC might be involved in the downregulation of autoreactive lymphocytes and result in the regulation of pathogenesis in autoimmune liver disease.     

Adenovirus-mediated delivery of soluble ST2 attenuates ovalbumin-induced allergic asthma in mice

Co-stimulatory molecules are important for regulating T cell activation and immune response. CD274 [programmed death ligand 1 (PD-L1), B7-H1] has emerged as an important immune modulator that can block T cell receptor signalling. We have investigated whether PD-L1 and other co-stimulatory ligands could be expressed in human B cells stimulated by cytosine-phosphate-guanosine (CpG)-DNA. CpG-DNA strongly induced the co-inhibitory molecule ligand, PD-L1, of human B cells. Results show that nuclear factor-kappa B (NF-κB) signalling is involved directly in CpG-DNA-induced PD-L1 expression in human B cells. We sought to determine the effect of CpG-DNA-treated B cells on T helper type 2 (Th2) cytokine production in Cry j 1 (Japanese pollen antigen)-stimulated human CD4-positive cells from patients with seasonal allergic rhinitis caused by Japanese cedar pollen. CpG-DNA-treated B cells reduced Cry j 1-induced interleukin (IL)-5 and IL-13 production in CD4-positive cells. When the binding of PD-1 to PD-L1 was inhibited by PD-1-immunoglobulin (Ig), this chimera molecule reversed the previously described reductions in IL-5 and IL-13 production. In contrast, the CpG B-treated B cells increased both interferon (IFN)-γ and IL-12 production in the presence of Cry j 1-stimulated CD4-positive cells. CpG-DNA simultaneously reduced the expression of B7RP-1 [also known as inducible co-stimulator ligand (ICOSL), B7-H2] and the ligand of CD30 (CD30L). These results indicate that CpG-DNA induces co-inhibitory molecule ligand PD-L1 expression in human B cells and PD-L1 can suppress Th2 cytokine production in Cry j 1-stimulated CD4-positive cells, while CpG-DNA increased Th1 cytokine production and reduced the expression of co-stimulatory molecule ligands that can promote Th2 inflammatory responses.