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At least 1,297 records · Page 72Linked to original sources
PubMed1999

CCR7 coordinates the primary immune response by establishing functional microenvironments in secondary lymphoid organs.

The proper function of immune surveillance requires well-coordinated mechanisms in order to guide the patrolling immune cells through peripheral tissues and into secondary lymphoid organs. Analyzing gene-targeted mice, we identified the chemokine receptor CCR7 as an important organizer of the primary immune response. CCR7-deficient mice show severely delayed kinetics regarding the antibody response and lack contact sensitivity and delayed type hypersensitivity reactions. Due to the impaired migration of lymphocytes, these animals reveal profound morphological alterations in all secondary lymphoid organs. Upon activation, mature skin dendritic cells fail to migrate into the draining lymph nodes. Thus, in order to bring together lymphocytes and dendritic cells to form the characteristic microarchitecture of secondary lymphoid organs, CCR7 is required to rapidly initiate an adoptive immune response.

Animals↗
PubMed2004

The equine thymus microenvironment: a morphological and immunohistochemical analysis.

We characterized herein the microarchitecture of the equine thymus along with post-natal development (6 months-->18 years). Thymuses showed an involutional process, beginning before the puberty and defined by five histological grades, which consider the progressive cortical thymocyte depletion, shrinkage and rearrangement of the epithelial network and increase in extracellular matrix (ECM). A second feature of the equine thymus was the presence of eosinopoiesis, erythropoiesis, mastocytopoiesis and plasmacytogenesis. Additionally, lymphatic vessels, full of lymphocytes, were particularly prominent. Distribution of ECM proteins was heterogeneous, being denser in the medulla, as well as basement membranes of capsule, septa and perivascular spaces, thus similar to the patterns seen in other mammals. In vitro, horse thymic nurse cells produce ECM proteins, which are relevant in thymocyte/epithelial cell interactions. In conclusion, the equine thymus presents morphological and involutional characteristics similar to other mammals, exhibiting particular features, as prominent non-lymphoid hematopoiesis and lymphatic vessels.

Animals↗
PubMedDate not supplied

Ontogeny of the thymus in a teleost fish, Cyprinus carpio L.: developing thymocytes in the epithelial microenvironment.

A monoclonal antibody, WCL9, specific for membrane molecules of a thymocyte subpopulation was used to detect these cells in situ during the ontogeny of thymus. Cryo-sections revealed WCL9+ cells in the rudiment of the thymus (day 4 post fertilization); thereafter, the positive cells were observed exclusively in the cortex from the first appearance of thymic regionalization (week 4 post fertilization) until adult age. Whole-mount immunostaining of the thymus with WCL9 revealed the three-dimensional structure of the cortex by specific staining. The presence and distribution of apoptotic cells during thymus development was studied by in situ end-labelling of fragmented DNA. From week 4 post fertilization onwards, apoptotic cells were more frequently detected in the cortex than medulla, suggesting a continuous selection of thymocytes in the cortex. Ultrastructural studies confirmed the presence of numerous cortical apoptotic cells inside macrophages. Electron microscopy provided evidence for the existence of epithelial heterogeneity in the thymus. During the ontogeny, the differentiation of epithelial cells was followed from the first weeks until the juvenile age. Cell types were classified on the basis of their localization and cytological characteristics as: i) limiting epithelial cells located in subcapsular, perivascular and peritrabecular zones; ii) reticular epithelial cells situated in medullary and cortical zones; iii) nurse-like cells at the border between the cortex and medulla, iiii) Hassall's body-like structures localized in the medulla. This study could suggest the occurrence of a wide range of lympho-epithelial interactions throughout thymocytes differentiation.

Animals↗
PubMed1999

Analysis of the mucosal microenvironment: factors determining successful responses to mucosal vaccines.

The predominance of IgA antibodies in mucosal sites reflects a combination of high rate IgA isotype switching among precursor cells in induction sites, their selective localisation in mucosal effector tissues and vigorous proliferation of these cells after extravasation. Each of these steps leading to IgA expression at the mucosa is under cytokine control. This paper will address the role of cytokines in induction and expression of IgA responses, the contribution of various precursor cell subsets and their differential responses to cytokine signals and strategies for manipulating cytokine expression. With respect to IgA antibody production in the gut whereas IL-4 and TGF-beta have been implicated in isotype switching of precursor cells to IgA commitment, their subsequent localisation, proliferation and effector activity expression is dependent on IL-5 and IL-6 expression locally. Most IgA plasma cells in the intestine derive from cells of the B2 lineage in the Peyer's patch, but a subpopulation of cells derived from the peritoneal cavity (B1 cells) also contribute to the IgA plasma cell population in the intestinal lamina propria. Whereas IgA+ cells of the B2 lineage are IL-6 dependent but IL-5 independent, B1-derived IgA+ cells are IL-5 dependent and IL-6 independent. On the other hand, cell mediated immune responses in the gut are highly dependent on IFN-gamma production by both Th1 CD4 cells and CD8 cells and in enteric Salmonella infection IFN-gamma production is essential but antibody has little effect on this process.Therapeutic interventions based on the information emerging from these studies will lead to improved vaccination responses and correction of immunodeficiencies especially in young animals.

Animals↗
PubMed1998

Normal cerebrospinal fluid suppresses the in vitro development of cytotoxic T cells: role of the brain microenvironment in CNS immune regulation.

The regulatory role of cerebrospinal fluid (CSF) in brain physiology is well established, while our understanding of its role in brain immunity is undefined. We demonstrate that normal rat CSF suppresses the in vitro development of mastocytoma-specific CTL activity in restimulated splenocytes from Balb/c mice, a strain unable to reject this tumor from the brain. Suppression is dependent on TGF-beta, revealed by reversal of suppression with specific neutralizing antibody. In contrast, mice which can reject this tumor from the brain, such as Balb/c mice with immunological memory to the tumor or CD-1 mice with major histo-incompatibility with the tumor, have populations of precursor CTL which are resistant to CSF-induced suppression, in the in vitro restimulation protocol. We propose that the susceptibility to CSF-induced suppression of peripherally generated immune cells that traffic to the brain plays an important role in determining whether growing tumor cells survive in the brain.

Animals↗
PubMed2000

The brain and thymus have much in common: a functional analysis of their microenvironments.

Research into the neural and immune systems has begun to converge. Since the first reports that interleukins play important roles in both systems and that lymphocytes secrete neuronal factors, scientists have been surprised by the ever-increasing list of interactions. Here, Rolf Mentlein and Marion Kendall examine the major supporting cells of the brain and thymus - astrocytes and thymic epithelial cells - the similar neuroectodermal origin of which could explain such fundamental analogies.

Animals↗
PubMed2002

Anthocyanin production from Vaccinium pahalae: limitations of the physical microenvironment.

Physical microenvironmental parameters conducive to production of flavonoids in vitro from continuous Vaccinium pahalae suspension cultures were examined first in shake flask culture experiments, and results were used to guide adaptations of a bioreactor production environment. Anthocyanin pigments were primarily concentrated in smaller aggregates up to 519 microm diameter. Agitation at 150 rpm and routine use of a mechanical scraper to periodically retrieve cells thrown out of solution was sufficient to keep productive plant cell aggregates in bioreactor suspension. A set up for enhanced irradiance with mercury lamps providing an average of 240 micromol m(-2) s(-1) PPF at the inner surface of the bioreactor vessel was required to sustain anthocyanin productivity through a 10-day production cycle.

Anthocyanins↗
PubMed2003

Simultaneous nitrification and denitrification by controlling vertical and horizontal microenvironment in a membrane-aerated biofilm reactor.

Nitrogen and carbon components in domestic modified wastewater were completely removed by simultaneous nitrification and denitrification using a membrane-aerated biofilm reactor where biofilm was fixed on a hollow-fiber membrane. To measure the spatial distribution of pH, ammonium and nitrate ions and to observe microbes inside the biofilm fixed on the membrane, microelectrodes and the fluorescence in situ hybridization (FISH) method were applied. Due to plug flow in the vertical direction (from the bottom to the top of the reactor), ammonium nitrogen was gradually removed and negligible nitrate nitrogen was detected throughout the reactor. FISH revealed that ammonia-oxidizing bacteria were mainly distributed inside the biofilm and other bacteria, which included denitrifying bacteria, were mainly distributed outside the biofilm and over the suspended sludge. In order to characterize bacterial activity in the vertical direction of the reactor, nitrification rates at lower, central and upper points were calculated using microelectrode data. The nitrification rate at the lower point was 7 and 125 times higher than those at the central and upper points, respectively. These results show that the removal of carbon and nitrogen compounds was accomplished efficiently by using various kinds of bacteria distributed vertically and horizontally in a single reactor.

Bacteria, Aerobic↗