Lipopolysaccharide-primed heterotolerant dendritic cells suppress experimental autoimmune uveoretinitis by multiple mechanisms

Exposure of bone-marrow-derived dendritic cells (BMDC) to high-dose ultrapure lipopolysaccharide for 24 hr (LPS-primed BMDC) enhances their potency in preventing inter-photoreceptor retinoid binding protein: complete Freund's adjuvant-induced experimental autoimmune uveoretinitis (EAU). LPS-primed BMDC are refractory to further exposure to LPS (= endotoxin tolerance), evidenced here by decreased phosphorylation of TANK-binding kinase 1, interferon regulatory factor 3 (IRF3), c-Jun N-terminal kinase and p38 mitogen-activated protein kinase as well as impaired nuclear translocation of nuclear factor κB (NF-κB) and IRF3, resulting in reduced tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-12 and interferon-β secretion. LPS-primed BMDC also show reduced surface expression of Toll-like receptor-4 and up-regulation of CD14, followed by increased apoptosis, mediated via nuclear factor of activated T cells (NFATc)-2 signalling. LPS-primed BMDC are not only homotolerant to LPS but are heterotolerant to alternative pathogen-associated molecular pattern ligands, such as mycobacterial protein extract (Mycobacterium tuberculosis). Specifically, while M. tuberculosis protein extract induces secretion of IL-1β, TNF-α and IL-6 in unprimed BMDC, LPS-primed BMDC fail to secrete these cytokines in response to M. tuberculosis. We propose that LPS priming of BMDC, by exposure to high doses of LPS for 24 hr, stabilizes their tolerogenicity rather than promoting immunogenicity, and does so by multiple mechanisms, namely (i) generation of tolerogenic apoptotic BMDC through CD14:NFATc signalling; (ii) reduction of NF-κB and IRF3 signalling and downstream pro-inflammatory cytokine production; and (iii) blockade of inflammasome activation

Colitis in a transgenic mouse model of autoimmune uveitis may be induced by neoantigen presentation in the bowel

Undifferentiated uveitis (intraocular inflammation, IOI) is an idiopathic sight-threatening, presumed autoimmune disease, accountable for ~ 10% of all blindness in the developed world. We have investigated the association of uveitis with inflammatory bowel disease (IBD) using a mouse model of spontaneous experimental autoimmune uveoretinitis (EAU). Mice expressing the transgene (Tg) hen egg lysozyme (HEL) in the retina crossed with 3A9 mice expressing a transgenic HEL-specific TCR spontaneously develop uveoretinitis at post-partum day (P)20/21. Double transgenic (dTg TCR/HEL) mice also spontaneously develop clinical signs of colitis at ~ P30 with diarrhoea, bowel shortening, oedema and lamina propria (LP) inflammatory cell infiltration. Single (s)Tg TCR (3A9) mice also show increased histological LP cell infiltration but no bowel shortening and diarrhoea. dTg TCR/HEL mice are profoundly lymphopenic at weaning. In addition, dTg TCR/HEL mice contain myeloid cells which express MHC Class II-HEL peptide complexes (MHCII-HEL), not only in the inflamed retina but also in the colon and have the potential for antigen presentation. In this model the lymphopenia and reduction in the absolute Treg numbers in dTg TCR/HEL mice is sufficient to initiate eye disease. We suggest that cell-associated antigen released from the inflamed eye can activate colonic HEL-specific T cells which, in a microbial micro-environment, not only cause colitis but feedback to amplify IOI

Environmental controls, morphodynamic processes, and ecogeomorphic interactions of barchan to parabolic dune transformations

The transformation of barchans into parabolic dunes has been observed in various dune systems around the world. Precise details of how environmental controls influence the dune transformation and stabilisation mechanism, however, remain poorly understood. A ‘horns-anchoring’ mechanism and a ‘nebkhas-initiation’ mechanism have previously been proposed and selected environmental controls on the transformation have been explored by some modelling efforts, but the morphodynamic processes and eco-geomorphic interactions involved are unclear and comparison between different dune systems is challenging. This study extends a cellular automaton model, informed by empirical data from fieldwork and remote sensing, to fully explore how vegetation characteristics, boundary conditions, and wind regime influence the transformation process and the resulting dune morphologies. A ‘dynamic growth function’ is introduced for clump-like perennials to differentiate between growing and non-growing seasons and to simulate the development of young plants into mature plants over multiple years. Modelling results show that environmental parameters interact with each other in a complex manner to impact the transformation process. The study finds a fundamental power-law relation between a non-dimensional parameter group, so-called the ‘dune stabilising index’ (S⁎), and the normalised migration distance of the transforming dune, which can be used to reconstruct paleo-environmental conditions and monitor the impacts of changes in climate or land-use on a dune system. Four basic eco-geomorphic interaction zones are identified which bear different functionality in the barchan to parabolic dune transformation. The roles of different environmental controls in changing the eco-geomorphic interaction zones, transforming processes, and resulting dune morphologies are also clarified

Transformation of parabolic dunes into mobile barchans triggered by environmental change and anthropogenic disturbance

Parabolic dunes are widely distributed on coasts and margins of deserts and steppes where ecosystems are vulnerable and sensitive to environmental changes and human disturbances. Some studies have indicated that vegetated parabolic dunes can be activated into highly mobile barchan dunes and the catastrophic shift of eco-geomorphic systems is detrimental to land management and social-economic development; however, no detailed study has clarified the physical processes and eco-geomorphic interactions that control the stability of a parabolic dune and its resistance to unfavorable environmental changes. This study utilizes the Extended-DECAL (Discrete Eco-geomorphic Aeolian Landscapes) model, parameterized by field measurements of dune topography and vegetation characteristics combined with remote sensing, to explore how increases in drought stress, wind strength, and grazing stress may lead to the activation of stabilizing parabolic dunes into highly mobile barchans. The modeling results suggest that the mobility of an initial parabolic dune at the onset of a perturbation determines the capacity of a system to absorb environmental change, and a slight increase in vegetation cover of an initial parabolic dune can increase the activation threshold significantly. The characteristics of four eco-geomorphic interaction zones control the processes and resulting morphologies of the transformations. A higher deposition tolerance of vegetation increases the activation threshold of the dune transformation under both a negative climatic impact and an increased sand transport rate, whereas the erosion tolerance of vegetation influences the patterns of resulting barchans (a single barchan versus multiple barchans). The change in the characteristics of eco-geomorphic interaction zones may indirectly reflect the dune stability and predict an ongoing transformation, whilst the activation angle may be potentially used as a proxy of environmental stresses. In contrast to the natural environmental changes that tend to affect relatively weak and young plants, grazing stress can exert a broader impact on any plant indistinctively. A small increase in grazing stress just above the activation threshold can accelerate dune activation significantly

The location and orientation of coastal parabolic sand dunes in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Geography at Massey University

No previous research into either the spatial diversity of different coastal sand dune types, or the factors influencing the location and morphology of any particular dune type has been done in New Zealand. Vertical aerial photographs were used to locate Holocene dunefields around the New Zealand coastline. The locations of dunefields in general and the spatial diversity of dune types are able to be explained by identifying the conditions most suitable for sand dune development and examining the spatial variation in these conditions. One particular dune type, parabolic, was examined in more detail in order to discover the relative importance of different variables to the development of that dune type. The relationship between wind climate and the location and morphology of coastal parabolic sand dunes was examined in detail. Wind data from coastal sites around New Zealand were used to compute sand transport vectors using two methods - one proposed by Landsberg (1956) and the other by Fryberger (1979) - and these were compared with dune orientations obtained from aerial photographs. Although Fryberger's method has never previously been applied to coastal sand dunes, the two methods were found to produce very similar results. Spatial variation of other aspects of dune morphology, such as the shape of parabolic dunes, were also compared to wind climate characteristics. Such comparisons were permitted by applying further calculations proposed by Fryberger which allow the directional variablity of wind to be expressed in exact terms. The results of these studies indicate that morphological characteristics of parabolic sand dunes, such as orientation, shape and size, are largely controlled by the strength and frequency of onshore winds and the directional variability of winds. Sand transport resultants computed using the Fryberger method were found to be closely aligned to dune orientations in most cases. This study provides some insight into the processes and variables affecting spatial variation of coastal sand dune development in New Zealand but also highlights the need for more detailed geomorphic studies of coastal dunefields in New Zealand

Culture and Characterization of Microglia from the Adult Murine Retina

Purpose. To develop a protocol for isolating and culturing murine adult retinal microglia and to characterize the phenotype and function of the cultured cells. Method. Retinal single-cell suspensions were prepared from adult MF1 mice. Culture conditions including culture medium, growth factors, seeding cell density, and purification of microglia from the mixed cultures were optimised. Cultured retinal microglial cells were phenotyped using the surface markers CD45, CD11b, and F4/80. Their ability to secrete proinflammatory cytokines in response to lipopolysaccharide (LPS) stimulation was examined using cytometric bead array (CBA) assay. Results. Higher yield was obtained when retinal single-cell suspension was cultured at the density of 0.75×106 cells per cm2 in Dulbecco’s modified Eagle medium (DMEM)/F12 + Glutamax supplement with 20% fetal calf serum (FCS) and 20% L929 supernatant. We identified day 10 to be the optimum day of microglial isolation. Over 98% of the cells isolated were positive for CD45, CD11b, and F4/80. After stimulating with LPS they were able to secrete proinflammatory cytokines such as IL-6 and TNF-α and express CD86, CD40, and MHC-II. Conclusion. We have developed a simple method for isolating and culturing retinal microglia from adult mice