Induction of regulatory T cells and dominant tolerance by dendritic cells incapable of full activation

Transplants tolerated through a process known as infectious tolerance evoke continuous recruitment of regulatory T (Treg) cells that are necessary to maintain the unresponsive state. This state is maintained long-term and requires continuous Ag exposure. It is not known, however, whether infectious tolerance operates through sustained recruitment of pre-existing regulatory cells, induction of regulatory cells, or both. Using mice deficient in natural Treg cells, we show here that quiescent donor dendritic cells (DC) laden with histocompatibility Ag can induce Treg cells de novo that mediate transplantation tolerance. In contrast, fully activated DC fail to do so. These findings suggest that DC incapable of delivering full activation signals to naive T cells may favor their polarization toward a regulatory phenotype. Furthermore, they suggest a role for quiescent endogenous DC in the maintenance of the tolerant state.     

Effects of agri-environment management for cirl buntings on other biodiversity

Agri-environment scheme (AES) management has increased populations of cirl buntings (Emberiza cirlus) in South Devon, England, and might be expected to provide benefits for other declining biodiversity, due to less intensive farm management. Fields managed under AES for cirl buntings (low-input spring barley or permanent pasture without inputs) were contrasted with control fields under conventional management (spring barley without management restrictions and winter cereals, or grazed without management restrictions) to identify such benefits for vascular plants, butterflies, bumblebees, carabid beetles, foliar invertebrates and bats. Activity-density and species richness of carabid beetles were both higher in AES spring barley fields than in control spring barley and winter cereal fields. Forb cover and abundance of butterflies and bumblebees were higher in AES spring barley fields than in winter cereals, but did not differ between AES and control spring barley. No difference was observed in plant species richness between any of the arable field types. Plant species richness and butterfly abundance were higher in AES pasture fields than in controls. Abundance, activity-density and/or species richness of other taxa did not differ between AES and control pastures. Benefits observed in AES spring barley fields arise from management specific to AES agreements, and also, we suggest, from the maintenance of spring-sown barley in the landscape. Benefits in AES pasture fields are ascribed to the absence of fertiliser and pesticide inputs, and reductions in stocking arising from this; there is also likely to have been some pre-selection for older pastures to be entered into AES management agreements. Agri-environment measures for cirl buntings have benefits for a range of taxa beyond the target species, and therefore, largely through reduction of management intensity and maintenance of land-use diversity, improve the overall biodiversity of the farmed landscape where they are present.     

Guild mobility affects spider diversity: Links between foraging behavior and sensitivity to adjacent vegetation structure

The movement patterns of species may affect their susceptibility to modified habitat structure. It is likely that sedentary species perceive habitat features at smaller spatial extents compared to mobile species, but there is a lack of experimental research on the effects of fine-scale habitat characteristics on organisms of differing mobility. Spiders display two basic mobility levels based on foraging behavior: web-building species are restricted to specific sites whereas active hunters are mobile. We collected spiders inhabiting sagebrush shrubs with a structurally enhanced, unmodified, or removed understory, to examine (1) whether habitat structure in the immediate vicinity of shrubs affected cursorial and web spiders differently in terms of abundance and species richness and (2) which genera most contributed to changes in community composition. Shrubs without understory had reduced cursorial spider densities and species richness compared to shrubs with added and unmodified understories, whereas web spiders lacked significant responses to treatments. Community-level differences based on relative abundance of genera were detected in cursorial spiders but not in web spiders, despite a strong contribution of the web-building genus Theridion to community dissimilarities. Our results support the hypothesis that sedentary organisms may be sensitive to contiguous habitat at finer spatial scales than cursorial organisms, and highlight the risks associated with only collecting local habitat information when studying mobile species.     

Patch shape alters spider community structure: links between microhabitat choice and sensitivity to increased edge habitat

Increased edge effects in fragmented habitats can affect the abundance of edge-dwelling organisms, but these impacts may depend on the biological attributes of species. Microhabitat choice, a species characteristic that reflects combinations of biological traits, may affect the ability of peripheral species to take advantage of increased edge habitat in the presence of edge effects. In this field study, we built artificial shrub modules designed to encourage web spiders to build webs on the periphery. While modules were identical in volume, they differed in shape (cubic and elongated), so that elongated modules had more edge habitat and were subject to enhanced edge effects. Given that the tangle-web spiders Theridion and Dictyna built webs on module edges and strongly differed in terms of concealment and substrate generalization, two habitat characteristics associated with lower vulnerability to habitat modification, we tested the hypothesis that Theridion, which built webs in more concealed locations and on a greater diversity of substrate configurations in the modules compared to Dictyna, would take better advantage of increased edge habitat. As predicted, Theridion was significantly more abundant on elongated modules whereas the abundance of Dictyna did not respond to shape, even though the change in module shape entailed a similar increase in favored substrate for both spider groups. Our results suggest that the microhabitat associations of organisms may be linked to their propensity to be sensitive to edges, and that a better understanding of these links can improve our ability to predict the effects of habitat modification on biodiversity.     

The human insulin receptor mRNA contains a functional internal ribosome entry segment

Regulation of mRNA translation is an important mechanism determining the level of expression of proteins in eukaryotic cells. Translation is most commonly initiated by cap-dependent scanning, but many eukaryotic mRNAs contain internal ribosome entry segments (IRESs), providing an alternative means of initiation capable of independent regulation. Here, we show by using dicistronic luciferase reporter vectors that the 5′-UTR of the mRNA encoding human insulin receptor (hIR) contains a functional IRES. RNAi-mediated knockdown showed that the protein PTB was required for maximum IRES activity. Electrophoretic mobility shift assays confirmed that PTB1, PTB2 and nPTB, but not unr or PTB4, bound to hIR mRNA, and deletion mapping implicated a CCU motif 448 nt upstream of the initiator AUG in PTB binding. The IR-IRES was functional in a number of cell lines, and most active in cells of neuronal origin, as assessed by luciferase reporter assays. The IRES was more active in confluent than sub-confluent cells, but activity did not change during differentiation of 3T3-L1 fibroblasts to adipocytes. IRES activity was stimulated by insulin in sub-confluent cells. The IRES may function to maintain expression of IR protein in tissues such as the brain where mRNA translation by cap-dependent scanning is less effective.