Altered monocyte-derived dendritic cell function in patients on hemodialysis: a culprit for underlying impaired immune responses

Background  

Patients with end-stage renal disease (ESRD) are known to have impaired immune function. Dendritic cells (DCs) are the major antigen-presenting cells that initiate primary immune responses, linking innate and adaptive immunity. Although suboptimal immune responses to vaccination, as frequently observed in ESRD patients, might suggest the presence of impaired DC function, the precise nature of altered DC function is not fully understood.     

Antigen presentation by renal tubular epithelial cells

The interaction between immune effector cells such as T lymphocytes and parenchymal cells in organ-specific immune injury is dynamic. It is now appreciated that the specificity, intensity, and eventual destructive effects of such interactions can be greatly influenced by responses of the target issue. Renal tubular cells are particularly well suited to participate in such immune collaborations. (1) They are exposed to innumerable potentially immunogenic peptides from blood and glomerular filtrate and have pathways to further process these peptides; (2) they express surface molecules which facilitate their engagement to T cells; and (3) they can produce proinflammatory cytokines. In the models of immune-mediated tubulointerstitial injury that are currently studied, there has been a great interest in defining the T lymphocytes that initiate, accelerate, or suppress disease. Surprisingly, there has been relatively little attention on defining the tubular cell responses that regulate these immune-mediated processes. This review will therefore focus on this intriguing aspect of immune tubular injury and relate what is known about antigen presentation by tubular cells in autoimmune renal disease.     

In vitro preparation and functional assessment of human monocyte-derived dendritic cells-potential antigen-specific modulators of in vivo immune responses

Dendritic cells (DCs) are highly specialized professional antigen presenting cells that have a potent capacity for stimulating na?ve, memory and effector T-cells. They are located in lymphoid organs as well as in almost all nonlymphoid tissues. Immature DCs, residing in the host microenvironment, respond to danger signals with maturation, a differentiation process along which they acquire the ability to direct the extent and the type of primary immune responses according to the type of danger perceived. In this review we present some of our approaches and experiences regarding the isolation of human monocytes from peripheral blood and the in vitro preparation of, first, immature and then mature DCs by applying several maturation factors: bacterial lipopolysaccharide (LPS), a defined mixture of recombinant pro-inflammatory cytokines, monocyte conditioned medium (MCM) and TNF-alpha alone. The assessment of DC phenotypes and their functional capabilities as well as some of the techniques used for tumour associated antigen loading are also presented. The results of such studies represent a basis for optimal in vitro preparation of DCs, which could be clinically used to modulate immune responses in cancer, autoimmune diseases and in the planned onset of tolerance to disparate major histocompatibilty complex (MHC) antigens prior to tissue or organ transplantation.     

In vitro preparation and functional assessment of human monocyte-derived dendritic cells—potential antigen-specific modulators of in vivo immune responses

Dendritic cells (DCs) are highly specialized professional antigen presenting cells that have a potent capacity for stimulating naïve, memory and effector T-cells. They are located in lymphoid organs as well as in almost all nonlymphoid tissues. Immature DCs, residing in the host microenvironment, respond to danger signals with maturation, a differentiation process along which they acquire the ability to direct the extent and the type of primary immune responses according to the type of danger perceived.In this review we present some of our approaches and experiences regarding the isolation of human monocytes from peripheral blood and the in vitro preparation of, first, immature and then mature DCs by applying several maturation factors: bacterial lipopolysaccharide (LPS), a defined mixture of recombinant pro-inflammatory cytokines, monocyte conditioned medium (MCM) and TNF-α alone. The assessment of DC phenotypes and their functional capabilities as well as some of the techniques used for tumour associated antigen loading are also presented. The results of such studies represent a basis for optimal in vitro preparation of DCs, which could be clinically used to modulate immune responses in cancer, autoimmune diseases and in the planned onset of tolerance to disparate major histocompatibilty complex (MHC) antigens prior to tissue or organ transplantation.     

Activation of human dendritic cells by porcine aortic endothelial cells: transactivation of na?ve T cells through costimulation and cytokine generation.

BACKGROUND: Dendritic cells (DC) are the most potent antigen-presenting cells in the immune system. To define the role of human DC in human anti-porcine immune responses, we defined the interaction of human DC with porcine aortic endothelial cells (PAEC). METHODS: To determine the immune responses, both monocyte-derived and peripheral blood DC were cultured with porcine and human endothelial cells. We analyzed the role of CD11a, CD11b, and CD54 in a cell-to-cell adhesion assay using antibodies against these molecules. The expression pattern of costimulatory molecules (CD40, CD80, CD86), adhesion molecules (CD54), and intracellular cytokines (interleukin-12p70 and tumor necrosis factor [TNF]-alpha) in DC after interaction with endothelial cells was determined by immunofluorescence. RESULTS: Human DC significantly adhered to PAEC (38-40%), and this adhesion was augmented (>50%) upon treatment with either recombinant swine interferon-gamma or recombinant human TNF-alpha. Addition of human DC to PAEC was blocked by pretreatment of DC with antibodies specific to human leukocyte function-associated antigen-1 or CD54. Adhesion of DC to PAEC also resulted in the activation of DC, which was manifested by up-regulation of costimulatory molecules (CD40, CD80, CD86), adhesion molecules (CD54), and HLA-DR. PAEC-activated human DC provided proliferative signals to the na?ve autologous CD4+ T cells and synthesized interleukin-12p70 and TNF-alpha. However, activated DCs failed to lyse PAEC in such interaction. CONCLUSION: Human DC effectively adhered to PAEC and were activated by xenoantigen, resulting in highly efficient antigen presentation and proliferation of CD4+ T cells. Further, this interaction of human DC to PAEC is regulated by the participation of costimulatory and adherence molecules and cytokines.     

Plasmacytoid dendritic cells: in vivo regulators of alloimmune reactivity?

Dendritic cells (DC) exhibit remarkable plasticity in terms of their ability to induce and regulate innate and adaptive immune responses. Human and mouse interferon alpha-producing plasmacytoid (p) DC have been found to regulate allogeneic T cell responses in vitro. Evidence is emerging that pDC may also regulate immune reactivity in vivo, including the responses that underlie graft-versus-host disease and organ transplant rejection. These cells may also offer potential for therapy of adverse immune responses and the promotion of tolerance induction.     

Interaction of Antithymocyte Globulins with Dendritic Cell Antigens

The polyclonal rabbit antithymocyte globulins (ATGs), Thymoglobulin and ATG‐Fresenius S, are widely used for prevention and therapy of allograft rejection and graft versus host disease. Dendritic cells (DC) govern immune responses and thus the interaction of ATGs with these cells could potentially contribute to the clinical effects of ATG therapy. Currently there is little information on the DC‐antigens targeted by ATGs. In this study we have used a new methodology to identify DC surface antigens recognized by ATGs. By screening an eukaryotic expression library generated from DC with ATGs we could identify several novel ATG antigens including CD81, CD82, CD98, CD99 and CD147. Furthermore, we engineered cells to express previously described ATG antigens and probed them with Thymoglobulin and ATG‐Fresenius S. Our results demonstrated strong binding to some but not all of these molecules. We show that previously described antigens and antigens identified in this study account for around 80% of the DC reactivity of ATGs. Analysis of molecules induced by ATG–DC interaction are more in support for an activation of these cells by ATGs than for a specific induction of a tolerogenic DC phenotype.     

基因修饰的树突状细胞疫苗诱导抗肿瘤免疫

树突状细胞是目前已知最有效的专职抗原提呈细胞,能诱导针对肿瘤的特异性细胞毒性T淋巴细胞反应,在抗肿瘤免疫中发挥着重要作用.运用树突状细胞的这一特性制备的肿瘤疫苗在体外和体内实验都已证明其抗肿瘤效应.近年来,基因修饰的树突状细胞疫苗由于其更出色的抗肿瘤效应成为研究的热点.本文就目前基因修饰的树突状细胞疫苗的研究现状,包括...     

趋化因子在树突状细胞肿瘤疫苗研究中的进展

趋化因子是一类调节免疫细胞定向迁移的细胞因子,其与表达于细胞表面的趋化因子受体结合而发挥生物学功能.树突状细胞(DC)是重要的专职抗原递呈细胞,其主要的应用是制备成各种肿瘤疫苗,树突状细胞功能的行使与趋化因子及其受体介导的细胞迁移密切相关,趋化因子在树突状细胞游走与迁徙过程中始终发挥着调节、促进或抑制的作用,从而促使树突状细胞递呈抗原、激活初始T细胞,引起机体免疫反应,杀伤、消灭肿瘤细胞和炎性分子.     

Generation of Primary Peptide-Specific CD8 Cytotoxic T-Lymphocytes In Vitro Using Allogeneic Dendritic Cells

Dendritic cells (DC) are potent antigen-presenting cells (APC) capable of inducing strong T-cell–mediated immunity. Infusion of lymphoma-specific antigen-loaded autologous DC has been demonstrated to result in the generation of antigen-specific immunity and reduction in tumor burden in B-cell lymphoma patients. Cellular immunotherapy employing antigen-loaded DC could have a potential therapeutic impact in tumors and viral infections, including HIV infection. However, DC in HIV-infected individuals and breast cancer patients are believed to be functionally defective. Therefore, the potential of using allogeneic DC offers significant implications for DC immunotherapy in AIDS and immunocompromised cancer patients. To explore the potential of allogeneic DC therapy in vivo, we tested the ability of allogeneic DC to generate primary peptide-specific CD8⁺ cytotoxic T-lymphocyte (CTL) responses in vitro. Our results indicate that DC from HLA class I-matched individuals elicit primary immune responses in vitro using viral peptides as naive antigens. A primary peptide-specific immune response could also be detected even when only one HLA allele (HLA-A10201) was matched between the allogeneic DC and T-lymphocytes. The ability to generate primary peptide-specific responses in vitro is strongly indicative of the in vivo therapeutic potential of allogeneic DC.     

The contribution of dendritic cells to immune responses against urological cancers

Dendritic cells (DC) play an essential role in initiating and directing primary immune responses. Their antigen uptake, migration, and interaction with T lymphocytes are regulated. Immunohistological studies of renal cell carcinomas, prostatic carcinomas, and transitional cell carcinomas suggest that these malignancies fail to recruit or activate DC. Tumor mediated inhibition of DC function may also occur by a variety of mechanisms. These data provide a rationale for the use of DC for active tumor immunotherapy. Initial data suggests that DC may help generate effective T lymphocyte responses against prostate cancer antigens and optimization of DC preparations, tumor antigenic material, and vaccination schedules are now priorities for therapeutic programs.     

Rabbit antithymocyte globulin inhibits monocyte-derived dendritic cells maturation in vitro and polarizes monocyte-derived dendritic cells towards tolerogenic dendritic cells expressing indoleamine 2,3-dioxygenase

BACKGROUND: Rabbit antithymocyte globulin (rATG) is a polyclonal mixture of immunoglobulin (Ig) G. It is used to prevent graft rejection and also graft versus host disease after transplantation. Its effect on lymphocyte function has been widely studied. Dendritic cells are central actors of the immune system. As antigen presenting cells, they are able to initiate, stimulate, and modulate immune responses. METHODS: In this study, we investigated rATG effects on in vitro differentiation and maturation of monocyte-derived dendritic cells (Mo-DCs). RESULTS: rATG inhibited maturation of immature Mo-DCs and allowed the generation of dendritic cells expressing ILT-3, CD123, CCR6 but not CCR7 and producing Indoleamine 2,3-dioxygenase mRNA as well as interferon-alpha. CONCLUSION: rATG polarizes in vitro Mo-DCs towards tolerogenic dendritic cells.     

Dendritic Cell-Based Immunotherapy for Glioma: Multiple Regimens and Implications in Clinical Trials

High grade glioma is a highly invasive brain tumor and recurrence is almost inevitable, even after radical resection of the tumor mass. Cytotoxic immune responses and immunological memory induced by immunotherapy might prevent tumor recurrence. Dendritic cells (DCs) are professional antigen-presenting cells of the innate immune system with the potential to generate robust antigen-specific T cell immune responses. DC-based immunotherapeutic strategies have been intensively studied in both preclinical and clinical settings. Although advances have been made in the experimental use of DCs, there are still considerable challenges that need to be addressed for clinical translation. In this review, we describe the variability of regimens currently available for DC-based immunotherapy and then review strategies to optimize DC therapeutic efficacy against glioma.     

Transduction of dendritic cell progenitors with a retroviral vector encoding viral interleukin-10 and enhanced green fluorescent protein allows purification of potentially tolerogenic antigen-presenting cells

BACKGROUND: Dendritic cells (DC) are important antigen-presenting cells that play critical roles in the initiation and modulation of immune responses. Genetic engineering of DC to express immunosuppressive molecules is a novel approach to the inhibition of allograft rejection. Retroviral delivery of viral interleukin (vIL)-10 to replicating myeloid DC progenitors (DCp) impairs their T-cell stimulatory capacity and promotes the induction of antigen-specific T-cell hyporesponsiveness. However, transduction efficiency with retroviral vectors is comparatively low. Enhanced green fluorescent protein (EGFP) is important both as a marker of gene transduction and for the selection of transduced cells. Our aims were to construct a retroviral vector encoding both vIL-10 and EGFP, to positively select transduced DC, and to assess the impact of these highly purified, vIL-10-secreting antigen-presenting cells on allogeneic T-cell responses. METHODS: DCp propagated from bone marrow of C57BL10 (H2b) mice in granulocyte-macrophage colony-stimulating factor (GM-CSF)+IL-4 were transduced with a retroviral vector encoding both vIL-10 and EGFP by centrifugal enhancement. Gene transfer efficiency was determined by flow cytometry. Transduced cells were flow sorted, and vIL-10 secretion was quantified by ELISA. DC function was assessed by the ability of the cells to induce naive allogeneic (C3H; H2k) T-cell proliferation and cytotoxic T lymphocyte generation. RESULTS: Retrovirally transduced DC expressed both vIL-10 and EGFP gene products. Approximately 20% of unsorted cells expressed EGFP, as determined by flow cytometry. vIL-10 was produced at a mean rate of 31 ng/40 hr/10(6) cells. After sorting, the incidence of EGFP+ DC was increased dramatically to at least 95%, and the production of vIL-10 was increased approximately three- to fourfold, to a mean of 107 ng/40 hr/10(6) cells. These highly purified, vIL-10-secreting DC exhibited markedly diminished capacity to induce allogeneic T-cell proliferative and cytotoxic responses. CONCLUSIONS: DCp retrovirally transduced to express both vIL-10 and EGFP can be rapidly identified and sorted to high levels of purity. The availability of highly enriched preparations of vIL-10-transduced DC facilitates studies of their immunoregulatory function and may enhance their therapeutic potential in transplantation or autoimmune disease.     

Active immunotherapy of prostate cancer with a focus on dendritic cells

Recurrent or metastatic prostate cancer is generally considered an incurable disease. Given the transient benefit from hormone deprivation therapy and limited successes of systemic chemotherapy, alternative treatment modalities are needed both in the situation of PSA recurrence and in hormone-refractory disease. Prostate cancer cells express several tumor associated antigens which are currently being evaluated as targets for active and specific immunotherapy approaches. Dendritic cells (DC) are the most powerful antigen-presenting cells (APC), able to prime naive T cells and to break peripheral tolerance and thus induce tumor immune responses. Close to 1000 prostate cancer patients have been treated with DC-based or other forms of active immunotherapy to date. Vaccination-induced immune responses have been reported in two thirds of DC trials, and favorable changes in the clinical course of the disease in almost half of the patients treated. Most responses, however, were modest and transient. Therefore, mechanisms of treatment failure and possibilities to improve vaccination efficacy are being discussed.     

Hyporesponsiveness in Alloreactive T-cells by NF-κB Inhibitor-Treated Dendritic Cells: Resistance to Calcineurin Inhibition

Dendritic cells (DC) are the most potent antigen-presenting cells (APC) initiating primary T-cell responses. Beyond this immunostimulatory function, certain DC subsets have been shown to induce T-cell tolerance in vitro and in vivo. In this study, immature monocyte-derived DC were activated in the presence of the NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC) and characterized with regard to phenotype, cytokine production and allostimulatory potential. Furthermore, the functional consequences of calcineurin inhibition were studied in T cells exposed to PDTC-modulated DC. We demonstrate that PDTC treatment of DC leads to an arrest in maturation as reflected by down-regulated major histocompatibility complex (MHC) antigens and costimulatory molecules, suppressed immunostimulatory cytokines and an impaired capability to support allogeneic T-cell activation. Allogeneic T cells challenged with PDTC-treated DC are refractory upon restimulation with alloantigens but not to polyclonal stimuli. Interestingly, the successful establishment of alloantigenic hyporesponsiveness is not prevented by concomitant calcineurin inhibition in vitro as well as in T cells from patients under cyclosporine A (CsA)-based immunosuppression ex vivo. These data may have important implications for the design of clinical regimens for the establishment of antidonor hyporeactivity in organ transplantation using in vitro-modulated DC.     

Current concepts in immunotherapy for the treatment of colorectal cancer

Immunotherapy could have a role in the therapy of colorectal cancer as there is now convincing evidence that the immune system can specifically recognize and destroy malignant cells. The MAb 17-1A has been used in advanced and primary disease, along with newer agents such as anti-epidermal growth factor receptor (EGFR) antibody. Immunotherapy with autologous tumour cell vaccine, genetic modification of immunostimulatory cytokines, suicide genes and TAAs as discussed. The multiplicity of peptide and carbohydrate antigens which can be potential targets for immunotherapy are also discussed. These include MUC1, Thomsen-Friedenreich and Sialosyl-Tn antigens and HER2 / neu. Active specific immunotherapy with the anti-idiotypic antibodies CEAVac and 105AD7, along with DC vaccines, is being currently used in adjuvant clinical trials. 105AD7 has been shown to cause significantly greater apoptosis of tumour cells in colorectal cancer patients, while CEAVac generated T cell proliferative anti-CEA responses. Dendritic cells pulsed with tumour mRNA or TAAs currently are being assessed in clinical trials. The role of HSPs in the anti-tumour immune response is discussed. Non-specific immunotherapeutic agents used in clinical trials with chemotherapeutic regimens have not shown any definitive benefit. Tumour progression may occur as result of escape from the host anti-cancer immune response. Better understanding of mechanisms of tumour evasion could explain why immunotherapy trials in patients have not shown better results. These include down-regulation of immune responses by the tumour, altered expression of MHC and/or TAAs by tumour cells, altered expression of adhesion molecules by tumour and/or DCs and usurpation of the immune response to the advantage of the cancer.     

Quantification of dendritic cell subsets in human renal tissue under normal and pathological conditions

Dendritic cells (DCs) play critical roles in immune responses and can be distinguished in two major subsets, myeloid and plasmacytoid DCs. Although the presence of DC in all peripheral organs, including the kidney, has been well documented, no accurate estimates of DC subsets in human kidneys have been reported. This study shows a detailed analysis of DC subsets in cryosections of human renal tissue. The cortex of normal kidneys contains at least two different HLA-DR(+) myeloid DC subtypes characterized by BDCA-1(+)DC-SIGN(+) and BDCA-1(+)DC-SIGN(-). The staining for DC-SIGN completely overlapped with CD68 in the renal interstitium. Unexpectedly, BDCA-2(+)DC-SIGN(-) plasmacytoid DCs are also abundantly present. Both subsets are located in the tubulo-interstitium often with a high frequency around, but rarely observed within glomeruli. Quantification of BDCA-1(+), DC-SIGN(+), and BDCA-2(+) cells in normal human renal tissue (pretransplant biopsy living donors; n=21) revealed that BDCA-1 is about four times as frequently present as BDCA-2. A preliminary cross-sectional analysis of DC in diseased kidneys, including rejection and immunoglobulin A nephropathy, revealed that the number of DC as well as their anatomical distribution might change under pathophysiological conditions. In conclusion, we show that human kidneys contain a dense network of myeloid and plasmacytoid DCs and provide the tools for phenotyping and enumeration of these cells to better understand interindividual differences in immune responses.     

Dendritic cell immunotherapy for patients with metastatic renal cell carcinoma: University of Tokyo experience

BACKGROUND: Dendritic cells (DC) are the most potent antigen-presenting cells and induce host antitumor immunity through the T-cell response. A clinical study of immunotherapy using cultured DC loaded with tumor antigen, for patients with metastatic renal cell carcinoma (RCC) was performed. METHODS: Dendritic cells were generated by culturing monocytes from peripheral blood for 7 days in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4. On day 6 the DC were pulsed with lysate from autologous tumor as the antigen and with keyhole limpet hemocyanin (KLH) as immunomodulator. The patients were given four doses of lysate-pulsed DC by intradermal injection with a 2-week interval between doses. Clinical effect and immune response were, respectively, evaluated by radiological examination and delayed-type hypersensitivity (DTH) test. RESULTS: Three patients were enrolled and the immunotherapy was well tolerated without significant toxicity. The vaccination induced a positive DTH reaction to tumor lysate in two patients and to KLH in all patients. Clinical responses consisted of one case of no change and two cases of progression of disease. However, we did not see a significant reduction of tumor volume in any case. CONCLUSION: Dendritic cell vaccination can safely induce an immunological response against RCC. Further trials are needed to fully evaluate its efficacy.