Survival strategy of Echinococcus multilocularis in the human host

As exemplified by aborted calcified liver lesions commonly found in patients from endemic areas, Echinococcus multilocularis metacestodes develop only in a minority of individuals exposed to infection with the papasite. Clinical research has disclosed some aspects of the survival strategy of E. multilocularis in human hosts. Clinical observations in liver transplantation and AIDS suggest that suppression of cellular/Th1related immunity increases disease severity. Most of the studies have stressed a role for CD8+ T cells and for Interleukin-10 in the development of tolerance. A spontaneous secretion of IL-10 by the PBMC seems to be the immunological hallmark of patients with progressive forms of alveolar echinococcosis (AE). IL-10-induced inhibition of effector macrophages, but also of antigen-presenting dendritic cells, may be operating and allowing parasite growth and survival. The genetic correlates of susceptibility to infection with E. multilocularis are clearer in humans than in the mouse model. A significant link between MHC polymorphism and clinical presentation of AE has been shown, and the spontaneous secretion of IL-10 in patients with a progressive AE is higher in patients with the HLA DR3+, DQ2+ haplotype. Clustering of cases in certain families, in communities otherwise exposed to similar risk factors, also points to immuno-genetic predisposition factors that may allow the larva to escape host immunity more easily. The first stage of larval development may be crucial in producing danger signals stimulating the initial production of cytokines. Therapeutic use of Interferon alpha is an attempt to foil the survival strategy of E. multilocularis. (C) 2005 Elsevier Ireland Ltd. All rights reserved.

The mononuclear phagocyte system

The mononuclear phagocyte system (MPS) has been defined as a family of cells comprising bone marrow progenitors, blood monocytes and tissue macrophages. Macrophages are a major cell population in most of the tissues in the body, and their numbers increase further in inflammation, wounding and malignancy. Their trophic roles for other cell types in development and homeostasis are becoming increasingly evident. The receptor for macrophage colony-stimulating factor (CSF-1R) is expressed in a large proportion of cells considered to be mononuclear phagocytes, including antigen-presenting dendritic cells, which can be considered a specialized adaptive state rather than a separate lineage. The unity of the MPS is challenged by evidence that there is a separate embryonic phagocyte lineage, by the transdifferentiation and fusion of MPS cells with other cell types, and by evidence of local renewal of tissue macrophage populations as opposed to monocyte recruitment. The concept of the MPS may have partly outlived its usefulness.

Assessment of epidermal cell viability by near infrared multi-photon microscopy following ballistic delivery of gold micro-particles

The use of gene guns in ballistically delivering DNA vaccine coated gold micro-particles to skin can potentially damage targeted cells, therefore influencing transfection efficiencies. In this paper, we assess cell death in the viable epidermis by non-invasive near infrared two-photon microscopy following micro-particle bombardment of murine skin. We show that the ballistic delivery of micro-particles to the viable epidermis can result in localised cell death. Furthermore, experimental results show the degree of cell death is dependant on the number of micro-particles delivered per unit of tissue surface area. Micro-particles densities of 0.16 +/- 0.27 (mean +/- S.D.), 1.35 +/- 0.285 and 2.72 +/- 0.47 per 1000 mu m(2) resulted in percent deaths of 3.96 +/- 5.22, 45.91 +/- 10.89, 90.52 +/- 12.28, respectively. These results suggest that optimization of transfection by genes administered with gene guns is - among other effects - a compromise of micro-particle payload and cell death. (c) 2005 Elsevier Ltd. All rights reserved.

Downregulation of IgE antibody and allergic responses in the lung by epidermal biolistic microparticle delivery

Background: Biolistic injections provide a needle-free delivery of antigen-laden microparticles to the epithelium. The precision of the injection preferentially targets the Langerhans cell network, which, although ideal for vaccination, might not be suitable for the downregulation of immune responses in immunotherapy. Objective: We sought to determine the ability of biolistic injection of antigen into the epithelium of sensitized mice to inhibit IgE antibody and lung inflammatory responses produced by further exposure to antigen. Methods: Mice were sensitized by means of a needle injection of ovalbumin (OVA) in alum and given a series of biolistic injections of OVA or vehicle control, followed by a boost of OVA in alum. Serum IgE and IgG antibodies were measured before and after the boost. The mice were then challenged intranasally, and the infiltration of inflammatory cells was measured by means of bronchoalveolar lavage. Airway reactivity of the challenged mice was measured by examining responses to methacholine with forced oscillatory techniques. Results: Biolistic injection of OVA into the dorsal skin of sensitized mice markedly inhibited IgE and IgG1 antibody responses induced by boosting. IgG2a antibody responses were reduced rather than stimulated. The eosinophilic inflammation in the bronchoalveolar lavage fluid induced by intranasal challenge was also markedly inhibited. Lung hyperreactivity showed an initial increase and then a decrease of responsiveness to methacholine, with elastance returning to the level of unsensitized mice. Biolistic injection into the buccal epithelium was also inhibitory. Conclusions: Biolistic injection of allergen inhibited the boosting of IgE antibody and eosinophilic lung inflammatory responses without inducing TO immunity.

DNA Motifs Suppressing TLR9 Responses

Immune cells respond to bacterial DNA containing unmethylated CpG motifs via Toll-like receptor 9 (TLR9). Given the apparent role of TLR9 in development of systemic lupus erythernatosus (SLE), there is interest in the development of TLR9 inhibitors. TLR9-mediated responses are reported to be inhibited by a confusing variety of different DNA sequences and structures. To aid characterization, we have provisionally categorized TLR9-inhibitory oligodeoxynucleoti des (ODN) into 4 classes, on the basis of sequence and probable mode of action. Class I are short G-rich ODN, which show sequence-specific inhibition of all TLR9 responses, and may be direct competitive inhibitors for DNA binding to TLR9. Class II are telomeric repeat motifs that inhibit STAT signaling, and thus are not specific to TLR9 responses. Because Class II ODN are generally made as 24-base phosphorothioate-modified ODN (PS-ODN), they also fall into Class IV, defined as long PS-ODN, which inhibit TLR9 responses in a sequence-nonspecific manner. Class III includes oligo (dG) that forms a 4-stranded structure and inhibits DNA uptake. The Class I G-rich motifs show the most promise as selective and potent TLR9 inhibitors for therapeutic applications.

Fractal analysis of pyramidal cells in the visual cortex of the galago (Otolemur garnetti): Regional variation in dendritic branching patterns between visual areas

Previously it has been shown that the branching pattern of pyramidal cells varies markedly between different cortical areas in simian primates. These differences are thought to influence the functional complexity of the cells. In particular, there is a progressive increase in the fractal dimension of pyramidal cells with anterior progression through cortical areas in the occipitotemporal (OT) visual stream, including the primary visual area (V1), the second visual area (V2), the dorsolateral area (DL, corresponding to the fourth visual area) and inferotemporal cortex (IT). However, there are as yet no data on the fractal dimension of these neurons in prosimian primates. Here we focused on the nocturnal prosimian galago (Otolemur garnetti). The fractal dimension (D), and aspect ratio (a measure of branching symmetry), was determined for I I I layer III pyramidal cells in V1, V2, DL and IT. We found, as in simian primates, that the fractal dimension of neurons increased with anterior progression from V1 through V2, DL, and IT. Two important conclusions can be drawn from these results: (1) the trend for increasing branching complexity with anterior progression through OT areas was likely to be present in a common primate ancestor, and (2) specialization in neuron structure more likely facilitates object recognition than spectral processing.

A population of HLA-DR+ immature cells accumulates in the blood dendritic cell compartment of patients with different types of cancer

Dendritic cell (DC) defects are an important component of immunosuppression in cancer. Here, we assessed whether cancer could affect circulating DC populations and its correlation with tumor progression. The blood DC compartment was evaluated in 136 patients with breast cancer, prostate cancer, and malignant glioma. Phenotypic, quantitative, and functional analyses were performed at various stages of disease. Patients had significantly fewer circulating myeloid (CD11c(+)) and plasmacytoid (CD123(+)) DC, and a concurrent accumulation of CD11c(-)CD123(-) immature cells that expressed high levels of HLA-DR+ immature cells (DR+IC). Although DR+IC exhibited a limited expression of markers ascribed to mature hematopoietic lineages, expression of HLA-DR, CD40, and CD86 suggested a role as antigen-presenting cells. Nevertheless, DR+IC had reduced capacity to capture antigens and elicited poor proliferation and interferon-gamma secretion by T-lymphocytes. Importantly, increased numbers of DR+IC correlated with disease status. Patients with metastatic breast cancer showed a larger number of DR+IC in the circulation than patients with local/nodal disease. Similarly, in patients with fully resected glioma, the proportion of DR+IC in the blood increased when evaluation indicated tumor recurrence. Reduction of blood DC correlating with accumulation of a population of immature cells with poor immunologic function may be associated with increased immunodeficiency observed in cancer.

Gap-junction communication between subtypes of direction-selective ganglion cells in the developing retina

The On-Off direction-selective ganglion cells (DSGCs) in the rabbit retina comprise four distinct subtypes that respond preferentially to image motion in four orthogonal directions; each subtype forms a regular territorial array, which is overlapped by the other three arrays. In this study, ganglion cells in the developing retina were injected with Neurobiotin, a gap-junction-permeable tracer, and the DSGCs were identified by their characteristic type 1 bistratified (BiS1) morphology. The complex patterns of tracer coupling shown by the BiSl ganglion cells changed systematically during the course of postnatal development. BiSl cells appear to be coupled together around the time of birth, but, over the next 10 days, BiSl cells decouple from each other, leading to the mature pattern in which only one subtype is coupled. At about postnatal day 5, before the ganglion cells become visually responsive, each of the BiSl cells commonly showed tracer coupling both to a regular array of neighboring BiSl cells, presumably destined to be DSGCs of the same subtype, and to a regular array of overlapping BiSl cells, presumably destined to be DSGCs of a different subtype. The gap-junction intercellular communication between subtypes of DSGCs with different preferred directions may play an important role in the differentiation of their synaptic connectivity, with respect to either the inputs that DSGCs receive from retinal interneurons or the outputs that DSGCs make to geniculate neurons. (C) 2004 Wiley-Liss, Inc.

Type 1 nitrergic (ND1) cells of the rabbit retina: Comparison with other axon-bearing amacrine cells

NADPH diaphorase (NADPHd) histochemistry labels two types of nitrergic amacrine cells in the rabbit retina. Both the large ND1 cells and the small ND2 cells stratify in the middle of the inner plexiform layer, and their overlapping processes produce a dense plexus, which makes it difficult to trace the morphology of single cells. The complete morphology of the ND1 amacrine cells has been revealed by injecting Neurobiotin into large round somata in the inner nuclear layer, which resulted in the labelling of amacrine cells whose proximal morphology and stratification matched those of the ND1 cells stained by NADPHd histochemistry. The Neurobiotin-injected ND1 cells showed strong homologous tracer coupling to surrounding ND1 cells, and double-labelling experiments confirmed that these coupled cells showed NADPHd reactivity. The ND1 amacrine cells branch in stratum 3 of the inner plexiform layer, where they produce a sparsely branched dendritic tree of 400-600 mum diameter in ventral peripheral retina. In addition, each cell gives rise to several fine beaded processes, which arise either from a side branch of the dendritic tree or from the tapering of a distal dendrite. These axon-like processes branch successively within the vicinity of the dendritic field before extending, with little or no further branching, for 3-5 mm from the soma in ventral peripheral retina. Consequently, these cells may span one-third of the visual field of each eye, and their spatial extent appears to be greater than that of most other types of axon-bearing amacrine cells injected with Neurobiotin in this study. The morphology and tracer-coupling pattern of the ND1 cells are compared with those of confirmed type 1 catecholaminergic cells, a presumptive type 2 catecholaminergic cell, the type 1 polyaxonal. cells, the long-range amacrine cells, a novel type of axon-bearing cell that also branches in stratum 3, and a type of displaced amacrine cell that may correspond to the type 2 polyaxonal cell. (C) 2004 Wiley-Liss, Inc.

The type 1 polyaxonal amacrine cells of the rabbit retina: A tracer-coupling study

The type 1 polyaxonal (PA1) cell is a distinct type of axon-bearing amacrine cell whose soma commonly occupies an interstitial position in the inner plexiform layer; the proximal branches of the sparse dendritic tree produce 1-4 axon-like processes, which form an extensive axonal arbor that is concentric with the smaller dendritic tree (Dacey, 1989; Famiglietti, 1992a,b). In this study, intracellular injections of Neurobiotin have revealed the complete dendritic and axonal morphology of the PA1 cells in the rabbit retina, as well as labeling the local array of PA1 cells through homologous tracer coupling. The dendritic-field area of the PA1 cells increased from a minimum of 0.15 mm(2) (0.44-mm equivalent diameter) on the visual streak to a maximum of 0.67 mm(2) (0.92-mm diameter) in the far periphery; the axonal-field area also showed a 3-fold variation across the retina, ranging from 3.1 mm(2) (2.0-mm diameter) to 10.2 mm(2) (3.6-mm diameter). The increase in dendritic- and axonal-field size was accompanied by a reduction in cell density, from 60 cells/mm(2) in the visual streak to 20 cells/mm(2) in the far periphery, so that the PA1 cells showed a 12 times overlap of their dendritic fields across the retina and a 200-300 times overlap of their axonal fields. Consequently, the axonal plexus was much denser than the dendritic plexus, with each square millimeter of retina containing similar to100 mm of dendrites and similar to1000 mm of axonal processes. The strong homologous tracer coupling revealed that similar to45% of the PA1 somata were located in the inner nuclear layer, similar to50% in the inner plexiform layer, and similar to5% in the ganglion cell layer. In addition, the Neurobiotin-injected PA1 cells sometimes showed clear heterologous tracer coupling to a regular array of small ganglion cells, which were present at half the density of the PA1 cells. The PA1 cells were also shown to contain elevated levels of gamma-aminobutyric acid (GABA), like other axon-bearing amacrine cells.

Alterations in the phenotype of neocortical pyramidal cells in the Dyrk1A+/- mouse

The gene encoding the dual-specificity tyrosine-regulated kinase DYRK1A maps to the chromosomal segment HSA21q22.2, which lies within the Down syndrome critical region. The reduction in brain size and behavioral defects observed in mice lacking one copy of the murine homologue Dyrk1A (Dyrk1A+/-) support the idea that this kinase may be involved in monosomy 21 associated mental retardation. However, the structural basis of these behavioral defects remains unclear. In the present work, we have analyzed the microstructure of cortical circuitry in the Dyrk1A+/- mouse and control littermates by intracellular injection of Lucifer Yellow in fixed cortical tissue. We found that labeled pyramidal cells were considerably smaller, less branched and less spinous in the cortex of Dyrk1A+/- mice than in control littermates. These results suggest that Dyrk1A influences the size and complexity of pyramidal cells, and thus their capability to integrate information. (c) 2005 Elsevier Inc. All rights reserved.

Density and morphology of dendritic spines in mouse neocortex

Dendritic spines of pyramidal cells are the main postsynaptic targets of cortical excitatory synapses and as such, they are fundamental both in neuronal plasticity and for the integration of excitatory inputs to pyramidal neurons. There is significant variation in the number and density of dendritic spines among pyramidal cells located in different cortical areas and species, especially in primates. This variation is believed to contribute to functional differences reported among cortical areas. In this study, we analyzed the density of dendritic spines in the motor, somatosensory and visuo-temporal regions of the mouse cerebral cortex. Over 17,000 individual spines on the basal dendrites of layer III pyramidal neurons were drawn and their morphologies compared among these cortical regions. In contrast to previous observations in primates, there was no significant difference in the density of spines along the dendrites of neurons in the mouse. However, systematic differences in spine dimensions (spine head size and spine neck length) were detected, whereby the largest spines were found in the motor region, followed by those in the somatosensory region and those in visuo-temporal region. (c) 2005 IBRO. Published by Elsevier Ltd. All rights reserved.

Ipsilateral corticocortical projections to the primary and middle temporal visual areas of the primate cerebral cortex: area-specific variations in the morphology of connectionally identified pyramidal cells

We quantified the morphology of over 350 pyramidal neurons with identified ipsilateral corticocortical projections to the primary (V1) and middle temporal (MT) visual areas of the marmoset monkey, following intracellular injection of Lucifer Yellow into retrogradely labelled cells. Paralleling the results of studies in which randomly sampled pyramidal cells were injected, we found that the size of the basal dendritic tree of connectionally identified cells differed between cortical areas, as did the branching complexity and spine density. We found no systematic relationship between dendritic tree structure and axon target or length. Instead, the size of the basal dendritic tree increased roughly in relation to increasing distance from the occipital pole, irrespective of the length of the connection or the cortical layer in which the neurons were located. For example, cells in the second visual area had some of the smallest and least complex dendritic trees irrespective of whether they projected to V1 or MT, while those in the dorsolateral area (DL) were among the largest and most complex. We also observed that systematic differences in spine number were more marked among V1-projecting cells than MT-projecting cells. These data demonstrate that the previously documented systematic differences in pyramidal cell morphology between areas cannot simply be attributed to variable proportions of neurons projecting to different targets, in the various areas. Moreover, they suggest that mechanisms intrinsic to the area in which neurons are located are strong determinants of basal dendritic field structure.