CD8+ T cells mediate ultraviolet A-induced immunomodulation in a model of extracorporeal photochemotherapy

Extracorporeal photochemotherapy (ECP) that takes advantage of the immunomodulatory effects of UV light has been extensively used for many years for the treatment of several T cell–mediated diseases, including graft-versus-host disease (GvHD) and systemic scleroderma. Immune mechanisms that lead to the establishment of T cell tolerance in ECP-treated patients remain poorly known. In this study, we have tested the effect of UV/psoralen-treated BM-derived dendritic cells, referred to as ECP-BMDCs on the outcome of an antigen-specific T cell-mediated reaction, that is, contact hypersensitivity (CHS), which is mediated by CD8⁺ effector T cells (CD8⁺T_eff). The intravenous (i.v.) injection of antigen-pulsed ECP-BMDCs in recipient C57BL/6 mice induced specific CD8⁺ T cells endowed with immunomodulatory properties (referred to as CD8⁺T_ECP), which prevented the priming of CD8⁺T_eff and the development of CHS, independently of conventional CD4⁺ regulatory T cells. CD8⁺T_ECP mediated tolerance by inhibiting the migration and functions of skin DC and subsequently the priming of CD8⁺T_eff. CD8⁺T_ECP displayed none of the phenotypes of the usual CD8⁺T regulatory cells described so far. Our results reveal an underestimated participation of CD8⁺ T cells to ECP-induced immunomodulation that could explain the therapeutic effects of ECP in T cell-mediated diseases.     

Extracorporeal photopheresis affects co-stimulatory molecule expression and interleukin-10 production by dendritic cells in graft-versus-host disease patients

Graft-versus-host disease (GVHD) is a major complication of allogeneic bone marrow transplantation. Extracorporeal photochemotherapy (ECP) has been introduced as an alternative treatment for GVHD refractory to conventional immunosuppressive treatment, although its mechanism of action is not yet clear. We investigated, in seven GVHD patients, the effects of ECP on dendritic cell maturation and cytokine production in an in vitro model that could mimic the potential in vivo effect of reinfusion of ECP-treated peripheral blood mononuclear cells. The model was based on co-culture of ECP-treated lymphocytes with monocyte-derived dendritic cells (DCs) of the same patient. We found that the co-culture of ECP-treated lymphocytes with immature DCs reduced CD54, CD40 and CD86 mean fluorescence intensity (MFI) significantly after lipopolysaccharide (LPS) stimulation, without affecting human leucocyte antigen D-related and CD80 MFI. In the same co-culture model, DCs produced increased amounts of interleukin (IL)-10 when co-cultured with ECP-treated lymphocytes and stimulated with LPS, while IL-12 and tumour necrosis factor-alpha production were not affected. These results suggest that reinfusion of large numbers of autologous apoptotic lymphocytes is significant for the therapeutic outcome of ECP through down-regulation of co-stimulatory molecules on DCs, inducing non-fully mature DCs with a low signal 2 and up-regulation of IL-10, which is an immunosuppressive cytokine.     

Immune privilege induced by regulatory T cells in transplantation tolerance

Summary:  Immune privilege was originally believed to be associated with particular organs, such as the testes, brain, the anterior chamber of the eye, and the placenta, which need to be protected from any excessive inflammatory activity. It is now becoming clear, however, that immune privilege can be acquired locally in many different tissues in response to inflammation, but particularly due to the action of regulatory T cells (Tregs) induced by the deliberate therapeutic manipulation of the immune system toward tolerance. In this review, we consider the interplay between Tregs, dendritic cells, and the graft itself and the resulting local protective mechanisms that are coordinated to maintain the tolerant state. We discuss how both anti-inflammatory cytokines and negative costimulatory interactions can elicit a number of interrelated mechanisms to regulate both T-cell and antigen-presenting cell activity, for example, by catabolism of the amino acids tryptophan and arginine and the induction of hemoxygenase and carbon monoxide. The induction of local immune privilege has implications for the design of therapeutic regimens and the monitoring of the tolerant status of patients being weaned off immunosuppression.     

Immunological mechanisms of sublingual immunotherapy

Administration of allergen-specific immunotherapy by the oral route, sublingual immunotherapy (SLIT), has been shown to be effective, with an improved safety profile compared with subcutaneous administration. However, the precise mechanisms underlying the induction of immune tolerance by SLIT remain unclear. Contact of the allergen with the antigen-presenting cells in oral mucosa is likely to be critical. Mucosal Langerhans cells can capture the allergen and transport it to local lymph nodes, which may favour the induction of T lymphocytes that suppress the allergic response. In addition, the production of blocking IgG4 antibodies and the involvement of mucosal B cells appear to play a role. There is a growing evidence to support the role of regulatory T cells in controlling the development of asthma and allergic disease. Nevertheless, there remains a lack of firm evidence that SLIT induces regulatory T cells, although preliminary in vitro data suggest that SLIT may increase interleukin-10, which has a clear role in suppressing the allergic immune response. Further studies are required to determine the involvement of regulatory T cells, the role of different dendritic cell subsets, mucosal B cells as well as the potential use of adjuvants during SLIT.     

Monocytes show immunoregulatory capacity on CD4+ T cells in a human in-vitro model of extracorporeal photopheresis

Extracorporeal photopheresis (ECP) is a widely used immunomodulatory therapy for the treatment of various T cell-mediated disorders such as cutaneous T cell lymphoma (CTCL), graft-versus-host disease (GvHD) or systemic sclerosis. Although clinical benefits of ECP are already well described, the underlying mechanism of action of ECP is not yet fully understood. Knowledge on the fate of CD14⁺ monocytes in the context of ECP is particularly limited and controversial. Here, we investigated the immunoregulatory function of ECP treated monocytes on T cells in an in-vitro ECP model. We show that ECP-treated monocytes significantly induce proinflammatory T cell types in co-cultured T cells, while anti-inflammatory T cells remain unaffected. Furthermore, we found significantly reduced proliferation rates of T cells after co-culture with ECP-treated monocytes. Both changes in interleukin secretion and proliferation were dependent on cell-contact between monocytes and T cells. Interestingly, blocking interactions of programmed death ligand 1 (PD-L1) to programmed death 1 (PD-1) in the in-vitro model led to a significant recovery of T cell proliferation. These results set the base for further studies on the mechanism of ECP, especially the regulatory role of ECP-treated monocytes.     

Immune monitoring as prerequisite for transplantation tolerance trials

Ever since its first application in clinical medicine, scientists have been urged to induce tolerance towards foreign allogeneic transplants and thus avoid rejection by the recipient's immune system. This would circumvent chronic use of immunosuppressive drugs (IS) and thus avoid development of IS‐induced side effects, which are contributing to the still unsatisfactory long‐term graft and patient survival after solid organ transplantation. Although manifold strategies of tolerance induction have been described in preclinical models, only three therapeutic approaches have been utilized successfully in a still small number of patients. These approaches are based on (i) IS withdrawal in spontaneous operational tolerant (SOT) patients, (ii) induction of a mixed chimerism and (iii) adoptive transfer of regulatory cells. Results of clinical trials utilizing these approaches show that tolerance induction does not work in all patients. Thus, there is a need for reliable biomarkers, which can be used for patient selection and post‐therapeutic immune monitoring of safety, success and failure. In this review, we summarize recent achievements in the identification and validation of such immunological assays and biomarkers, focusing mainly on kidney and liver transplantation. From the published findings so far, it has become clear that indicative biomarkers may vary between different therapeutic approaches applied and organs transplanted. Also, patient numbers studied so far are very small. This is the main reason why nearly all described parameters lack validation and reproducibility testing in large clinical trials, and are therefore not yet suitable for clinical practice.     

大鼠心脏移植后淋巴细胞5种免疫分子表达的变化

目的：观察大鼠异体异位心脏移植术后不同时间点，淋巴细胞相关免疫分子的表达水平、供心存活率及心肌组织的病理学改变，探讨免疫排斥反应的相关时间进程。方法：分别经供体SD大鼠的心脏主动脉、肺动脉与受体Wistar大鼠的腹主动脉及下腔静脉吻合，进行异位心脏移植术。于术前及术后不同时间点，取血分离淋巴细胞。用流式细胞仪分别检测淋巴细胞上CD4、CD8、IL-2R、ICAM-Ⅰ和MHC-Ⅱ类分子的表达水平。对供心心肌组织进行常规病理学检查。结果：于移植后24h，只有MHC-Ⅱ类分子的表达水平增加，CD4、IL-2R和ICAM—Ⅰ的表达水平降低，CD8无改变。术后72h，CD4、CD8及IL．2R的表达增加，其中CD8和IL-2R达峰值。术后7～10d，除CD4的表达继续增加外，其他4种免疫分子的表达水平逐渐降低。术后不同时间点移植心脏的存活率分别为：100％(24h)、85．7％(72h)、16．7％(7d)、0(10d和12d)。病理学检查显示，移植后24h，心肌组织无明显的病理学变化，术后3d，7只大鼠中4只出现ⅠA级及以上病理改变。术后7d，6只大鼠全部发生Ⅱ级以上的病理学变化。结论：大鼠心脏移植后的24h内，外周血淋巴细胞为以MHC-Ⅱ分子表达为主的抗原识别、呈递期，并伴有一过性免疫功能降低；术后24—72h为T细胞活化期，术后3-7d为免疫排斥反应效应期。CD4、CD8和IL-2R等免疫分子表达的峰值与开始出现轻度排斥反应时病理学变化的时间相一致。     

免疫耐受机制研究进展

免疫耐受是机体免疫系统在接触某种抗原后所产生的对该抗原特异性免疫无应答状态,是免疫应答的一种特殊形式,免疫应答的复杂性决定了免疫耐受诱导的复杂性和困难性.随着免疫学的发展,人们对免疫耐受产生机制有了较多的认识.本文对免疫耐受与细胞凋亡、调节性T细胞及树突状细胞的研究进展进行综述.     

超声心动图对心脏移植监测的多种效应

背景：急性排斥反应是关系到心脏移植后能否长期存活的关键因素之一,因此及时发现并控制急性排斥反应在临床实践中尤为重要。目的：探讨心脏移植后超声心动图检测的临床意义。方法：通过检索近年来关于超声心动图对移植心脏进行检查的临床研究及动物实验相关文献,分析移植心脏心动图特点,供者心脏在受者体内发生的结构和功能的变化,测量并比较相关指标,以评价超声心动图在心脏移植急性排斥反应中的价值。结果与结论：超声心动图检查可及时无创的监测心脏移植后排斥反应,在移植前受体评价、移植中监测及移植后随访中都为临床诊治提供重要的参考依据,但由于病例数较少,且由于心脏移植患者在移植后的不同时间段进行检测,可能对研究的结果造成影响,有待于今后对心脏移植患者在移植后的相同时间段进行评价,使研究结果更具有可比性及准确性。 中国组织工程研究杂志出版内容重点：肾移植;肝移植;移植;心脏移植;组织移植;皮肤移植;皮瓣移植;血管移植;器官移植;组织工程全文链接：     

Impact of infection on transplantation tolerance

Allograft tolerance is the ultimate goal of organ transplantation. Current strategies for tolerance induction mainly focus on inhibiting alloreactive T cells while promoting regulatory immune cells. Pathogenic infections may have direct impact on both effector and regulatory cell populations, therefore can alter host susceptibility to transplantation tolerance induction as well as impair the quality and stability of tolerance once induced. In this review, we will discuss existing data demonstrating the effect of infections on transplantation tolerance, with particular emphasis on the role of the stage of infection (acute, chronic, or latent) and the stage of tolerance (induction or maintenance) in this infection‐tolerance interaction. While the deleterious effect of acute infection on tolerance is mainly driven by proinflammatory cytokines induced shortly after the infection, chronic infection may generate exhausted T cells that could in fact facilitate transplantation tolerance. In addition to pathogenic infections, commensal intestinal microbiota also has numerous significant immunomodulatory effects that can shape the host alloimmunity following transplantation. A comprehensive understanding of these mechanisms is crucial for the development of therapeutic strategies for robustly inducing and stably maintaining transplantation tolerance while preserving host anti‐pathogen immunity in clinically relevant scenarios.     

Tolerogenic dendritic cells and their applications in transplantation

In transplantation immunology, the ultimate goal is always to successfully and specifically induce immune tolerance of allografts. Tolerogenic dendritic cells (tol-DCs) with immunoregulatory functions have attracted much attention as they play important roles in inducing and maintaining immune tolerance. Here, we focused on tol-DCs that have the potential to promote immune tolerance after solid-organ transplantation. We focus on their development and interactions with other regulatory cells, and we also explore various tol-DC engineering protocols. Harnessing tol-DCs represents a promising cellular therapy for promoting long-term graft functional survival in transplant recipients that will most likely be achieved in the future.     

T helper frequencies in peripheral blood reflect donor-directed reactivity in the graft after clinical heart transplantation

We describe the usefulness of a fast (48-h) limiting dilution assay (LDA) for the enumeration of human alloreactive helper T lymphocytes (HTL) in the peripheral blood, in relation to histologically defined rejection grades after heart transplantation. HTL frequencies (HTLf) in pretransplant samples varied from patient to patient, ranging from 106 to 625 HTL/106 peripheral blood mononuclear cells (PBMC). In the first week after heart transplantation (HTx), when immunosuppression was instituted, HTLf were significant lower (range 30-190 HTL/106). The level of HTL in the first week after HTx when rejection grade was 0 or 1A (ISHLT score) was considered to be the baseline frequency. This frequency did not correlate with the number of subsequent rejection episodes. During rejection (grade 3), donor-specific HTLf were increased above their baseline frequencies (P = 0.01). Expressed as percentage of baseline frequencies, HTLf increased significantly during acute rejection (AR) compared with 1-2 weeks before rejection (P = 0.003). The increase was specific, since viral infections did not result in a rise of donor-specific HTL, while also HTLf specific for third party HLA antigens were not elevated during rejection. Monitoring HTLf in peripheral blood with a shortened (48-h) assay may serve as a non-invasive method for detecting intragraft immunological reactivity. Demonstrating absence of donor-specific reactivity may limit the number of invasive endomyocardial biopsy (EMB) procedures and allow tapering of immunosuppressive treatment.     

Regulatory T cells in autologous stem cell transplantation for autoimmune disease

Since a decade autologous stem cell transplantation (ASCT) is successfully performed to treat patients with severe autoimmune disease. However, the mechanism of action of this intervention remains largely unknown. Scarce data from animal studies and human clinical trials indicate that, besides extensive immune ablation, restoration of regulatory immune networks is of critical importance. This review focuses on the role of naturally occurring and induced regulatory T cells in controlling immune reconstitution and restoration of immune tolerance and in preventing relapses of disease following ASCT.     

Lymphocyte response in the early period after heart transplantation

The quantitative and qualitative composition of the leukocytes and dehydrogenase activity of the lymphocytes were determined in blood entering and leaving the transplanted heart at different times after grafting in dogs. A decrease in the lymphocyte count in blood flowing from the grafted heart was found, on account of retention of the lymphocytes in the graft; the activities of the mitochondrial dehydrogenases also were reversed as the result of contact of the lymphocytes with the foreign antigens of the transplanted heart. It is suggested that the mechanism of reversal is connected with the functions of the lymphocytes as immunocompetent cells.A. N. Bakulev Institute of Cardiovascular Surgery, Academy of Medical Sciences of the USSR, Moscow. Institute of Experimental Surgery, Slovak Academy of Sciences, Bratislava, Czechoslovakia. (Presented by Academician of the Academy of Medical Sciences of the USSR, P. A. Vershilova.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 6, pp. 704–708, June, 1978.     

清髓性和非清髓性干细胞移植后树突状细胞亚群的动态观察

探讨不同预处理方法移植后树突状细胞亚群早期重建情况。采用三色流式细胞仪动态检测不同移植方法后早期患者外周血树突状细胞亚群DC1(Lin-HLA-DR+CD11c+)、DC2(Lin-HLA-DR+CD123+)水平。结果:清髓性干细胞移植组包括同胞全相合干细胞移植和HLA半相合移植,移植后14dDC1分别为0.093%±0.091%,0.090%±0.064%,DC2为0.056%±0.026%,0.130%±0.036%,二者差别无统计意义。非清髓性干细胞移植组移植后14dDC1为0.223%±0.084%,DC2为0.360%±0.023%,非清髓性干细胞组DC1、DC2略低于正常对照组,和清髓性移植组相比,非清髓性干细胞组明显增高,P<0.05,二者差别有统计学意义。移植前的预处理方案强度影响树突状细胞亚群重建。     

Adrenomedullin, a neuropeptide with immunoregulatory properties induces semi-mature tolerogenic dendritic cells

Dendritic cells (DC) play a pivotal role in tolerance. Adrenomedullin (AM), a neuropeptide with anti-apoptotic and anti-inflammatory effects, may decrease T helper type 1 effector cells and induce regulatory T (Treg) cells. The aim of this study was to evaluate AM effects on murine dendritic cell (DC) maturation and functions. Bone marrow-derived DC were produced and stimulated with CpG motifs, lipopolysaccharide or AM for 24 hr. Then, DC maturation and expression of AM and AM receptors were evaluated. Compared with lipopolysaccharide-stimulated or CpG-stimulated DC, AM-stimulated DC had lower levels of co-stimulatory molecule expression and pro-inflammatory cytokine release. The AM induced high levels of interferon-γ but not of interleukin-10. Importantly, AM inhibited lipopolysaccharide-induced maturation of DC. However, allogeneic T-cell stimulation and endocytic capacity of AM-stimulated DC were comparable to those of semi-mature and mature DC. Moreover, DC expressed AM and its receptors at a basal level, and AM receptor expression increased with DC maturation. The AM stimulation induced indoleamine 2,3-dioxygenase (IDO) expression, promoting Treg cell expansion. For the first time, we describe the DC maturation phenotype by a neuropeptide (AM). We have demonstrated that AM and its receptors are expressed in DC and that exogenous AM can modify the DC phenotype and functions and can induce a semi-mature DC phenotype with IDO expression. These results indicate close interactions among immune system regulation mechanisms and calcitonin-like peptides.     

调节性T细胞在大鼠小肠移植急性排斥反应中的作用

目的 分析调节性T细胞在大鼠急性排斥反应中的作用。方法 采用免疫组化SABC染色法，测定BN→LEW大鼠小肠移植急性排斥反应时，外周血及移植肠浸润淋巴细胞中调节性T细胞：CD4^ ,CD8^ ,CD25^ T淋巴细胞及相关细胞因子IL－4和IFN－γ的表达，并与同基因大鼠间小肠移植（BN→BN）作比较。结果 外周血淋巴细胞分析显示，大鼠小肠移植急性排斥反应时，以CD4^ ,CD25^ ,T细胞为主，CD8^ 淋巴细胞只占少部分；分泌IL－4的细胞在术后4，7，14d分别只占14．3％，16．2％和16．9％。移植肠基底浸润的淋巴细胞以CD4^ ,CD25^＋和分泌IFN－γ的淋巴细胞为主。结论 在大鼠同种小肠移植中，急性排斥反应与CD25^ ,CD4^ T细胞及Th1相关细胞因子IFN－γ的表达增加相关。而CD8^＋T淋巴细胞和Th2相关细胞因子IL－4可能具有保护作用。     

肾移植后排斥与感染中细胞免疫功能的监测

背景：Cylex ImmuKnow检测方法是惟一得到FDA认可的检测移植受者细胞免疫功能的方法, 它直接反映细胞免疫的功能,具有灵敏度高、特异性强,结果量化等优点。 目的：通过对肾移植后患者监测细胞免疫功能iATP值(intracellular adenosine triphosphatei),分析细胞免疫功能与肾移植术后排斥或感染的关系。 方法：140例肾移植受者采用ImmuKnowTM-Cylex®方法检测细胞免疫功能,收集数据结合患者临床状态分为排斥组18例,感染组35例与稳定组87例,同时收集61份健康人群血样检测细胞免疫功能数据作对照。分析细胞免疫功能与肾移植患者移植后发生排斥与感染的关系。 结果与结论：细胞免疫功能iATP值检测结果显示,感染组患者有71.4%(n=25)分布在低免疫区,同比对照组、稳定组与排斥组比例明显增高(P < 0.05)。感染组iATP值显著低于其他3组。说明感染与细胞免疫功能低下两者具有明显的相关性,细胞免疫功能测定对监测肾移植后感染具有显著意义。提示ImmuKnowTM-Cylex®方法测定细胞免疫功能为肾移植后并发感染的诊断与治疗提供可靠客观依据,但与肾移植后排斥反应的发生未见明显的相关性,有待于大样本的实验证实。