Tumour-derived exosomes and their role in cancer-associated T-cell signalling defects

Dendritic and lymphoid ‘exosomes' regulate immune activation. Tumours release membranous material mimicking these ‘exosomes,' resulting in deletion of reactive lymphocytes. Tumour-derived ‘exosomes' have recently been explored as vaccines, without analysis of their immunologic consequences. This investigation examines the composition of tumour-derived ‘exosomes' and their effects on T lymphocytes. Membranous materials were isolated from ascites of ovarian cancer patients (n=6) and Western immunoblotting was performed for markers associated with ‘exosomes.' Using cultured T cells, ‘exosomes' were evaluated for suppression of CD3-ζ and JAK 3 expressions and induction of apoptosis, measured by DNA fragmentation. ‘Exosome' components mediating suppression of CD3-ζ were isolated by continuous eluting electrophoresis and examined by Western immunoblotting. ‘Exosomes' were shown to be identical with previously characterised shed membrane vesicles by protein staining and TSG101 expression. ‘Exosomes' expressed class I MHC, placental alkaline phosphatase, B23/nucleophosmin, and FasL. ‘Exosomes' suppressed expression of T-cell activation signalling components, CD3-ζ and JAK 3 and induced apoptosis. CD3-ζ suppression was mediated by two components: 26 and 42 kDa. Only the 42 kDa component reacted with anti-FasL antibody. These results indicate that, while ‘exosomes' express tumour antigens, leading to their proposed utility as tumour vaccines, they also can suppress T-cell signalling molecules and induce apoptosis

A Behavioral Change Perspective of Maroon Soil Fertility Management in Traditional Shifting Cultivation in Suriname

In Suriname, the Maroons have practiced shifting cultivation for generations, but now the increasing influence of modern society is causing a trend of decreasing fallow periods with potentially adverse effects for the vulnerable tropical soils. Adoption of appropriate soil fertility management (SFM) practices is currently slow. Combining methods from cultural ecology and environmental psychology, this study identifies two groups with divergent behavioral intentions which we term semi-permanent cultivators and shifting cultivators. Semi-permanent cultivators intend to practice more permanent agriculture and experiment individually with plot-level SFM. Shifting cultivators rely on traditional knowledge that is not adequate for their reduced fallow periods, but perceive constraints that prevent them practicing more permanent agriculture. Semi-permanent cultivators act as a strong reference group setting a subjective norm, yet feel no need to exchange knowledge with shifting cultivators who are in danger of feeling marginalized. Drawing on a political ecology perspective, we conclude that cultural ecological knowledge declined due to negative perceptions of external actors setting a strong subjective norm. Semi-permanent cultivators who wish to enter the market economy are most likely to adopt SFM. We conclude that any future SFM intervention must be based on an in-depth understanding of each group’s behavior, in order to avoid exacerbating processes of marginalization

Towards understanding the traits contributing to performance of pearl millet open-pollinated varieties in phosphorus-limited environments of West Africa

Aims Pearl millet [Pennisetum glaucum (L.) R. Br.] open-pollinated varieties, which are the predominant cultivars, have never been systematically evaluated for adaptation to low-soil phosphorus (P), a major constraint on pearl millet production in West Africa (WA). Methods We evaluated grain yield (GY), flowering time (FLO), harvest index (HI), and residual grain yields (RGY) of 102 open-pollinated varieties from WA under low-P (−P) and high-P (+P) field conditions in six environments of WA. In addition, PE-related traits of the varieties were evaluated at early growth stage in a pot experiment. Results Significant genetic variation was observed for GY, FLO, HI and PE-related traits. P-efficient varieties had higher yield under −P conditions. Varietal performance under −P varied across environments depending on FLO, relative flowering delay under −P (FD) and RGY measured in the field. Low-P-susceptible varieties had higher FLO, lower HI than low-P-tolerant varieties. Response to direct selection under −P field conditions was 20.1 g m−2, whereas indirect selection response under +P was 16.3 g m−2. Conclusions Selection under −P field conditions while taking into account seasonal variations for FLO, FD and PE is expected to be important for improving GY specifically targeting −P environments in WA

Assessing the Feasibility of Wetlands Conservation: Using Payments for Ecosystem Services in Pallisa, Uganda

This chapter reports on a study of the potential for payments for ecosystem services to encourage the adoption of more sustainable agricultural practices in the Pallisa district in southeastern Uganda. Due to low productivity and population pressure, the subsistence agriculture that dominates the upland areas is increasingly encroaching on wetland areas critical to a many ecosystem services. While encroachment is illegal, enforcement has not been effective, raising the possibility that a positive incentive mechanism might be a more effective approach to wetlands protection. This study began with a workshop designed to learn about the potential importance of wetlands and their services from local and national stakeholders, and to assess the legal and institutional setting in which environmental policy is being implemented. The next step was to implement a quantitative analysis of ecosystem service supply, to estimate the possible rates of participation by farmers in contracts for wetlands conservation and the impact on farmers’ incomes. The analysis suggests that payments for ecosystem services could be a viable alternative to conventional environmental regulation if local institutions can manage contracts with farmers at a reasonable cost, and if national and international beneficiaries are willing to pay for wetlands protection

Antigen processing and class II MHC peptide-loading compartments in human B-lymphoblastoid cells

The peptide/class II major histocompatibility complex (MHC) complexes recognized by CD4+ T cells have been characterized at the structural and biochemical levels and studies on the transport and maturation of class II MHC indicate that specialized sites may be involved in peptide acquisition. Here we report the characterization of the compartments involved in antigen processing and class II MHC loading relative to distinct functional domains of the endocytic pathway in antigen-specific human B lymphocytes. Peroxidase-mediated crosslinking analysis in intact cells demonstrates that peptide loading of class II MHC takes place in a compartment accessible to membrane immunoglobulin but not to transferrin receptors, although processing may be initiated within the latter domain. The density of membrane vesicles carrying newly assembled class II MHC complexes was distinct from early and late endosomes and dense lysosomes. Endocytosed antigen-gold complexes enter a class II MHC-rich compartment morphologically very similar to that described previously and within the time frame of biochemically detectable peptide loading