The role of dendritic cells in shaping the immune response

Dendritic cells are central to the initiation of primary immune responses. They are the only antigen-presenting cell capable of stimulating naive T cells, and hence they are pivotal in the generation of adaptive immunity. Dendritic cells also interact with and influence the response of cells of the innate immune system. The manner in which dendritic cells influence the responses in cells of both the innate and adaptive immune systems has consequences for the bias of the adaptive response that mediates immunity to infection after vaccination or infection. It also provides an opportunity to intervene and to influence the response, allowing ways of developing appropriate vaccination strategies. Mouse and human studies have identified myeloid, lymphoid and plasmacytoid dendritic cells. Studies in domesticated animals with agents of specific infectious diseases have confirmed the applicability of certain of the generic models developed from mice or from in vitro studies on human cells. In vivo and ex vivo studies in cattle have demonstrated the existence of a number of subpopulations of myeloid dendritic cells. These cells differ in their ability to stimulate T cells and in the cytokines that they produce, observations clearly having important implications for the bias of the T-cell response. Dendritic cells also interact with the innate immune system, inducing responses that potentially bias the subsequent adaptive response.     

Dendritic cells in cattle: phenotype and function

Dendritic cells are professional antigen presenting cells derived from the bone marrow and distributed throughout body tissues where they are located in sites that are suitable for antigen uptake. They are central to the induction of immune responses in naive animals and thus have become targets in strategies that are aimed at modulating resistance to infection. Studies in cattle have shown that the dendritic cells are phenotypically heterogeneous and that the different phenotypes have different biological properties. The molecular basis for this variation has begun to be investigated and has led to the identification of a member of the SIRPalpha family of signal regulatory proteins (MyD1) on a subset of dendritic cells in afferent lymph. Uptake of antigen by cattle dendritic cells is by a number of mechanisms that can involve endocytosis via clathrin coated pits or via caveolae as well as macropinocytosis.     

Canine dendritic cells from peripheral blood and lymph nodes

Canine dendritic cells were prepared from peripheral blood or lymph nodes using a series of steps including fractionation on bovine plasma albumin (BPA), irradiation with 4000 R, incubation for 16–18 hours, and refractionation on BPA. Dendritic cells were recovered in the low density (LD) fraction containing approximately 0.6% of the unfractionated cells. Measured by the incorporation of ³H-thymidine, the response of the high density (HD) cells to neuraminidase-galactose oxidase (NGO) was lower than that of the unfractionated lymph node cells (LNC) but increased in a concentration dependent manner after the addition of a population of cells enriched for dendritic cells (30–70% by morphologic criteria). Cooperation between HD- and LD- cells was not restricted to identity of the major histocompatibility complex. Canine dendritic cells also displayed stimulatory activity higher than unfractionated peripheral blood mononuclear cells (PBMC) in a one way mixed leukocyte culture (MLC). Canine dendritic cells were nonadherent to plastic, were of low density, and remained viable and functional after irradiation. For the first time, canine dendritic cells have been identified in peripheral blood and lymph nodes and have been shown to act as accessory cells in the response of lymphocytes to NGO and as stimulator cells in a MLC.     

树突状细胞抗肿瘤疫苗研究进展

树突状细胞(DC)是目前发现的抗原递呈功能最强的专职抗原递呈细胞.大量试验证明,DC疫苗在抗肿瘤免疫中发挥着重要的作用.随着分子生物学、免疫学、基因工程技术的发展,各种DC疫苗和DC细胞的治疗应运而生,发展迅速.文章就DC的生物学特性、DC与肿瘤发生与发展的关系、DC抗原的负载方法及其在临床试验中的应用进行了综述.     

Efficient generation of canine bone marrow-derived dendritic cells

Because of their unsurpassed potency in presenting antigens to naive T cells, dendritic cells are considered to be an important candidate in the development of immunotherapeutic strategies. Despite the high potential of dendritic cell-based immunotherapy, as a so-called dendritic cell vaccination, few clinical approaches using dendritic cell vaccination have been performed in the dog because of very limited information regarding the generation of canine dendritic cells and their functional properties. We therefore established a protocol for the efficient generation of dendritic cells from canine bone marrow cells using recombinant feline granulocyte-macrophage colony-stimulating factor and canine interleukin-4. Dendritic cells were generated efficiently: a yield of 1-9 x 10(6) cells per approximately 0.5 ml of canine bone marrow aspiration was achieved. These dendritic cells showed features shared with mouse and human dendritic cells: dendrite morphology, expression of surface markers MHC class II and CD11c, and up-regulation of molecules related to antigen presentation (MHC class II, B7-1, and B7-2) by activation with lipopolysaccharide. Moreover, the dendritic cells demonstrated phagocytic activity, processing activity of pinocytosed proteins, and activation of allogeneic T cells far more potent than that by macrophages. Our findings suggest that the bone marrow-derived dendritic cells are functional for the capturing and processing of antigens and the initiation of T cell responses.     

Bovine natural killer cells

Natural killer (NK) cells have received much attention due to their cytotoxic abilities, often with a focus on their implications for cancer and transplantation. But despite their name, NK cells are also potent producers of cytokines like interferon-gamma. Recent discoveries of their interplay with dendritic cells and T-cells have shown that NK cells participate significantly in the onset and shaping of adaptive cellular immune responses, and increasingly these cells have become associated with protection from viral, bacterial and parasitic infections. Furthermore, they are substantially present in the placenta, apparently participating in the establishment of normal pregnancy. Consequently, NK cells have entered arenas of particular relevance in veterinary immunology. Limited data still exist on these cells in domestic animal species, much due to the lack of specific markers. However, bovine NK cells can be identified as NKp46 (CD335) expressing, CD3(−) lymphocytes. Recent studies have indicated a role for NK cells in important infectious diseases of cattle, and identified important bovine NK receptor families, including multiple KIRs and a single Ly49. In this review we will briefly summarize the current understanding of general NK cell biology, and then present the knowledge obtained thus far in the bovine species.     

Generation of canine dendritic cells from peripheral blood monocytes without using purified cytokines

Dendritic cells (DCs), which differentiate in vitro from peripheral blood monocytes (PBMOs) or bone marrow precursors, are a promising candidate for immunotherapy against cancer. The dog, which suffers common types of cancers along with humans, make an ideal large animal model for cancer studies. Monocyte-derived DCs in the dog have not been well characterized, however, since the appropriate condition for in vitro differentiation has not been established. To tackle this problem, we have developed a conditioned media by culturing T cells with immobilized anti-canine CD3 antibody, and sought to induce differentiation of DCs from PBMOs. When purified CD14+ PBMOs were cultured in the presence of 25% T cell conditioned medium (TCCM), the PBMOs increased size and had extended dendritic processes by day 12 of the culture. The cultured PBMOs were found to increase the expression of MHC class II and CD1a molecules, and significantly increased stimulatory activity for allogeneic T cells in the mixed leukocyte reaction. Moreover, the cells significantly increased their expression of IL-18 and IFN-gamma when stimulated with polyinosinic-polycytidylic acid (Poly (I:C)). The cells have a reduced phagocytic activity, which is a common defect in mature DCs. It follows from these results that TCCM does induce the differentiation of DCs from PBMOs.     

Dendritic cells, implications on function from studies of the afferent lymph veiled cell

Studies of afferent lymph veiled cells (ALVC) show that the full biological function of dendritic cells in peripheral tissue is not explained by a simple model in which immature dendritic cells at the body surface take up antigen, migrate via the afferent lymph ducts, mature and then effectively present antigens to T-cells in the draining lymph node. Furthermore, it is evident from various investigations that the dendritic cells in afferent lymph draining from the body surfaces are not a homogeneous population of cells. They comprise a mixture of cell phenotypes defined by staining with monoclonal antibodies, and the different sub-populations have distinct biological functions and roles in vivo. The molecular basis for differences between the function of afferent lymph dendritic cell subsets is only now being explored and defined but some progress has been made in understanding the role of co-stimulatory molecules. It should be possible to exploit knowledge of the functions of these cells and aid future vaccination strategies in domesticated animals thereby improving animal health and reducing economic loss, and, as a consequence, improving human health. By deliberately targeting functionally distinct subsets of either precursor or mature dendritic cells in vivo, it should become feasible to achieve an appropriately biased immune response.     

Antigen presenting cells in mucosal sites of veterinary species

The ability of antigen presenting cells, in particular dendritic cells, to integrate a variety of environmental signals, together with their ability to respond appropriately by initiating either tolerance or defensive immune responses make them cells of particular relevance and importance in the mucosal environment. They have been demonstrated in a variety of mucosal tissues in veterinary species and have been characterized to varying degrees, showing that fundamental immunological principles apply throughout all species, but also highlighting some species differences. A major advantage of carrying out immunological research in veterinary species is their size: it is possible to cannulate lymphatic ducts and obtain information about cell migration between different tissues. It is also possible to obtain pure populations of relatively rare cell types such as the plasmacytoid dendritic cells or mucosal dendritic cells ex vivo for the study of immune responses to diseases in their natural host and for other thorough functional studies. Two major myeloid antigen presenting cell (APC) (dendritic cells, DC) cell populations have been described in gut draining lymph and other mucosal sites in ruminants and pigs, characterised by the presence or absence of surface molecules, their enzyme profiles, their ability to phagocytose and their different potential as APC. There is evidence that one of these subsets has migrated from the diffuse mucosal tissue, where it is found as a phagocytic as well as stimulatory APC population, which in turn may be derived from blood macrophages. In addition, the presence and role in viral infection of the IFN-alpha producing plasmacytoid DC in mucosal tissue is discussed, based on studies in pigs.     

Localized and disseminated histiocytic sarcoma of dendritic cell origin in dogs

Canine histiocytic proliferative disorders include a wide spectrum of diseases characterized by different biologic behaviors. The etiology and pathogenesis of these diseases are largely unknown. The clinicopathologic, morphologic and immunophenotypic characteristics of canine localized and disseminated histiocytic sarcoma were examined in 39 dogs. Rottweilers, Bernese Mountain Dogs, and retrievers were most commonly affected (79%). Localized histiocytic sarcomas (19 dogs) arose from a single site, and metastatic lesions were observed in draining lymph nodes. Predilection sites were subcutis and underlying tissues on extremities, but tumors occurred in other locations, including spleen, lung, brain, nasal cavity, and bone marrow. Disseminated histiocytic sarcomas (20 dogs), a multisystem disease previously described as malignant histiocytosis, primarily affected spleen, lungs, bone marrow, liver, and lymph nodes. Both localized and disseminated canine histiocytic sarcomas were composed of pleomorphic tumor cell populations. CD1+, CD4-, CD11c+, CD11d-, MHC II+, ICAM-1 +, Thy-1 +/- tumor cells were identified in all snap-frozen samples (31 dogs). This phenotype is characteristic for myeloid dendritic antigen-presenting cell lineage. Hence, canine localized and disseminated histiocytic sarcomas are likely myeloid dendritic cell sarcomas. Dendritic antigen-presenting cells are a heterogeneous cell population with regards to their ontogeny, phenotype, function, and localization. The exact sublineage of the proliferating dendritic antigen-presenting cells involved in canine histiocytic sarcomas remains to be determined. Phenotypic analysis of formalin-fixed tissues from eight dogs was limited by available markers. Morphologic features and the phenotype CD18+, CD3-, and CD79a- were the most useful criteria to indicate likely histiocytic origin.     

Immmunohistochemical study of the blood and lymphatic vasculature and the innervation of mouse gut and gut-associated lymphoid tissue

The blood and lymphatic vascular system of the gut plays an important role in tissue fluid homeostasis, nutrient absorption and immune surveillance. To obtain a better understanding of the anatomic basis of these functions, the blood and lymphatic vasculature of the lower segment of mouse gut and several constituents of gut-associated lymphoid tissue (GALT) including Peyer's patch, specialized lymphoid nodules in the caecum, small lymphoid aggregates and lymphoid nodules in the colon were studied by using confocal microscopy. Additionally, the innervation and nerve/immune cell interactions in the gut and Peyer's patch were investigated by using cell surface marker PGP9.5 and Glial fibrillary acidic protein (GFAP). In the gut and Peyer's patch, the nerves have contact with B cell, T cell and B220CD3 double-positive cells. Dendritic cells, the most important antigen-presenting cells, were closely apposed to some nerves. Some dendritic cells formed membrane-membrane contact with nerve terminals and neuron cell body. Many fine nerve fibres, which are indirectly detected by GFAP, have contact with dendritic cells and other immune cells in the Peyer's patch. Furthermore, the expression of Muscarinic Acetylcholine receptor (subtype M2) was characterized on dendritic cells and other cell population. These findings are expected to provide a route to understand the anatomic basis of neuron-immune regulation/cross-talk and probably neuroinvasion of prion pathogens in the gut and GALT.     

Malignant stromal cell tumor of the spleen in a WBN/Kob rat

Primary splenic stromal tumors have rarely been reported in rodents. We report the case of a 90-week-old male WBN/Kob rat with a nodular demarcated mass in the spleen, which was kept as a non-treated animal in a long-term animal study. Histopathology revealed round to short spindle-shaped tumor cells arranged in a solid growth pattern. Invasive growth, anisokaryosis, and high mitotic activity (46 per 10 high-power fields [2.37 mm²]) were observed to be multifocal, but most tumor cells showed mild nuclear pleomorphism. The pattern of silver impregnation corresponded to that of the marginal zone of the red pulp. Immunohistochemistry revealed that the tumor cells were double positive for fascin and desmin and focally positive for Iba-1 and OX-6 expression. These characteristics were similar to those observed in fibroblastic reticular cells and dendritic cells in the marginal zone of the red pulp. These findings suggest that the malignant stromal cell tumor of the spleen in this case had characteristics of both fibroblastic reticular cells and dendritic cells.     

多糖对树突状细胞功能的影响

树突状细胞（dendritic cells,DC）是目前已知机体内功能最强的抗原递呈细胞,也是惟一能启动初始T细胞介导免疫反应的一类细胞。论文综述了多糖对DC功能的影响,多糖能够刺激DC分裂增殖,同时能够显著地诱导DC成熟,能够有效增强DC表面分子表达与增强细胞因子分泌的能力,从而促进DC的抗原递呈能力。     

Species-specific properties and translational aspects of canine dendritic cells

Dogs are affected by spontaneously occurring neoplastic and inflammatory diseases which often share many similarities with pathological conditions in humans and are thus appreciated as important translational animal models. Dendritic cells (DCs) represent the most potent antigen presenting cell population. Besides their physiological function in the initiation of primary T cell responses and B cell immunity, a deregulation of DC function is involved in immune-mediated tissue damage, immunosuppression and transplantation complication in human and veterinary medicine. DCs represent a promising new target for cancer immunotherapy in dogs. However, the therapeutic use of canine DCs is restricted because of a lack of standardized isolation techniques and limited information about dog-specific properties of this cell type. This article reviews current protocols for the isolation and in vitro generation of canine monocyte- and bone marrow-derived DCs. DCs of dogs are characterized by unique morphological features, such as the presence of cytoplasmic projections and periodic microstructures. Canine DCs can be discriminated from other hematopoietic cells also based on phenotypic properties and their high T cell stimulatory capability in mixed leukocyte reactions. Furthermore, the classification of canine DC-derived neoplasms and the role of DCs in the pathogeneses of selected infectious, allergic and autoimmune diseases, which share similarities with human disorders, are discussed. Future research is needed to expand the existing knowledge about DC function in canine diseases as a prerequisite for the development of future therapies interfering with the immune response.     

Phenotype and function of murine discrete Peyer's patch macrophage derived - dendritic cells

The phenotype and function of peritoneal cavity macrophage-derived dendritic cells (PEC-DC) was previously reported. In this study we have gone further in using our established culture system to generated discrete Peyer's patch dendritic cells (DPP-DC) from murine discrete Peyer's patch macrophages (DPP-M?), following stimulation with granulocyte macrophage colony stimulating factor (GM-CSF) plus interleukin 4 (IL-4) for 7 days. DPP-M? from murine small intestines were obtained by mechanical disruption of discrete Peyer's patches (DPP), followed by metrizamide density gradient centrifugation to remove Peyer's patch resident DC and debri, after which an overnight adherent step in tissue culture medium was carried out for macrophage enrichment. Characterization of the generated DPP-DC was carried out using well-established criteria of morphology, expression of membrane antigens and capacity for antigen presentation. Dendritic cells expressed DEC-205, F4/80 and CD34 at high levels, but exhibited very low CD11c levels. They were shown to present soluble protein antigen to CD3(+) spleen T cells. A comparison of the surface antigen expression in the progenitor DPP-M? population and the generated DPP-DC showed a significant decrease in MHC class II levels and a marked down regulation of the co-stimulatory molecule CD86 (B7-2). High expression of the haemopoietic progenitor marker CD34 indicates that the generated DC, possess a haemopoietic rather than myeloid origin. Taken together, these results may provide a better understanding of the complex network regulating mucosal immune responses.     

植物多糖对动物免疫细胞的影响及调节机制研究进展

植物多糖是由10个或10个以上单糖聚合而成的大分子物质,是一类重要的生物活性天然产物,具有无毒副作用、来源广泛等特点,在调节动物机体免疫系统、预防疾病方面具有极高的利用价值。文章综述植物多糖对动物巨噬细胞、T淋巴细胞、B淋巴细胞和树突状细胞的影响及其可能的作用机制,为植物多糖在动物生产中的应用提供参考。     

Contribution of in vivo and ex vivo studies to understanding the role of antigen-presenting cells and T cell subsets in immunity to cattle diseases

In vivo and ex vivo studies of the immune system in relation to infectious disease that are carried out in the natural target species provide data that are relevant to understanding the biology of the immune cells and immunity to infection. This is particularly the case for diseases that show host specificity. Ex vivo studies that exploit the surgical cannulation of lymphatic ducts have allowed access to natural dendritic cells. Investigations of these cells have revealed the presence of subpopulations that differ in their ability to stimulate T cells and differ in the range of cytokines synthesized. These differences would be forecast to have major effects on the bias and type of immune response that are induced. Studies in vivo of the effect of depleting T-cell populations with monoclonal antibodies (mAbs) have shown how different T-cell populations have differing critical roles for different infectious diseases, and how they may contribute to the immune response and pathology after infection. Here the case is made for how studies in cattle have aided our understanding of immunity to several infections that can be exploited for the rational design of effective vaccination and control strategies.     

Reduced growth of calves and its reversal by use of anabolic agents

Disease has profound effects on the immune system, endocrine system, and on the growth process. Since diseases are catabolic to the animal, there is current interest in the possible role of anabolic hormones to counter the effects of disease in general and minimize the effects of a disease process on growth and development. A number of anabolic hormones, such as growth hormone (GH) and estradiol + progesterone (EP), have been studied for their role in enhancing growth and stimulating immune function and are thus candidates for hormonal intervention in disease processes. GH has been shown to be effective in countering some of the deleterious effects of endotoxemia but was ineffective in a parasitic disease model. Studies with EP have shown similar success with both endotoxemia and a parasitic disease model. Moreover, GH and EP do not share a common mechanism of action, suggesting that the effects are not simply due to anabolic actions. While the mechanism of action of GH in endotoxemia has been examined, the effects of EP are via an unknown mechanism, possibly by inhibition of IL-I action or inhibition of nitric oxide overproduction.     

Factors Involved in the Dissemination of Disease in Fish Populations

Abstract

Infectious diseases have been observed in both human and animal populations for millenia. Unlike diseases of “higher” animals, the dispersal of disease in fish populations rarely has been studied quantitatively. However, the principles that govern the spread of diseases of humans and other mammals should, with modification, be applicable to the study of infectious diseases in fishes. Disease in populations is a dynamic phenomenon; fluctuations in prevalence and impact are dependent on the interactions among host, pathogen, and environment. Models of the dynamics of infectious diseases in salmon and other fishes can be constructed and refined to reflect the characteristics of diseases by integrating the most important factors in the process. Among the factors that have been shown to be important in other systems are the “contagiousness” of the pathogen (transmission coefficient, β), duration of infection, host population density, development of immunity, and efficacy of therapeutants.     

DNA vaccines and their applications in veterinary practice: current perspectives

Inoculation of plasmid DNA, encoding an immunogenic protein gene of an infectious agent, stands out as a novel approach for developing new generation vaccines for prevention of infectious diseases of animals. The potential of DNA vaccines to act in presence of maternal antibodies, its stability and cost effectiveness and the non-requirement of cold chain have heightened the prospects. Even though great strides have been made in nucleic acid vaccination, still there are many areas that need further research for its wholesome practical implementation. Major areas of concern are vaccine delivery, designing of suitable vectors and cytotoxic T cell responses. Also, the induction of immune responses by DNA vaccines is inconclusive due to the lack of knowledge regarding the concentration of the protein expressed in vivo. Alternative delivery systems having higher transfection efficiency and the use of cytokines, as immunomodulators, needs to be further explored. Recently, efforts are being made to modulate and prolong the active life of dendritic cells, in order to make antigen presentation a more efficacious one. For combating diseases like acquired immunodeficiency syndrome (AIDS), influenza, malaria and tuberculosis in humans; and foot and mouth disease, Aujesky’s disease, swine fever, rabies, canine distemper and brucellosis in animals, DNA vaccine clinical trials are underway. This review highlights the salient features of DNA vaccines, and measures to enhance their efficacy so as to devise an effective and novel vaccination strategy against animal diseases.