Enhanced positive selection of a transgenic TCR by a restriction element that does not permit negative selection

Very little is known about the conformational properties of the MHC molecules that are able to signal positive selection of a given TCR. To try to understand these parameters and to determine whether these requirements are shared with interactions during negative selection and antigen recognition, we have studied selection and antigen recognition of a transgenic TCR (specific for lymphocytic choriomeningitls virus glycoprotein and H-2Db) in the context of two Db mutants, H-2bm13 and H-2bm14. The data showed that the transgenic TCR was not positively selected by the H-2bm14 haplotype but, interestingly, enhanced positive selection was seen in H-2bm13 mice. The transgenic TCR could not be negatively selected In H-2bm13animals persistently infected with the virus (neonatal virus carrier mice), nor could the transgenic TCR be activated by H-2bm13 infected cells in vivo or in vitro. These experiments show that although a TCR may be selected by a mutant MHC molecule, the corresponding viral antigen cannot be recognized in the context of the mutant MHC molecule, as Judged by both negative selection and T cell reactivity in vivo and in vitro. The ‘enhanced' positive selection occurring in the context of Dbm13 suggests that a different conformation of the MHC molecule is able to select the same TCR and also that various TCR-ligand avidities may permit positive selectio

One Body Density Matrix, Natural Orbits and Quasi Hole States in 16O and 40Ca

The one body density matrix, momentum distribution, natural orbits and quasi hole states of 16O and 40Ca are analyzed in the framework of the correlated basis function theory using state dependent correlations with central and tensor components. Fermi hypernetted chain integral equations and single operator chain approximation are employed to sum cluster diagrams at all orders. The optimal trial wave function is determined by means of the variational principle and the realistic Argonne v8' two-nucleon and Urbana IX three-nucleon interactions. The correlated momentum distributions are in good agreement with the available variational Monte Carlo results and show the well known enhancement at large momentum values with respect to the independent particle model. Diagonalization of the density matrix provides the natural orbits and their occupation numbers. Correlations deplete the occupation number of the first natural orbitals by more than 10%. The first following ones result instead occupied by a few percent. Jastrow correlations lower the spectroscopic factors of the valence states by a few percent (~1-3%) and an additional ~8-12% depletion is provided by tensor correlations. It is confirmed that short range correlations do not explain the spectroscopic factors extracted from (e,e'p) experiments. 2h-1p perturbative corrections in the correlated basis are expected to provide most of the remaining strength, as in nuclear matter.Comment: 25 pages, 9 figures. Submitted to Phys.Rev.

Enhanced positive selection of a transgenic TCR by a restriction element that does not permit negative selection

Very little is known about the conformational properties of the MHC molecules that are able to signal positive selection of a given TCR. To try to understand these parameters and to determine whether these requirements are shared with interactions during negative selection and antigen recognition, we have studied selection and antigen recognition of a transgenic TCR (specific for lymphocytic choriomeningitls virus glycoprotein and H-2Db) in the context of two Db mutants, H-2bm13 and H-2bm14. The data showed that the transgenic TCR was not positively selected by the H-2bm14 haplotype but, interestingly, enhanced positive selection was seen in H-2bm13 mice. The transgenic TCR could not be negatively selected In H-2bm13animals persistently infected with the virus (neonatal virus carrier mice), nor could the transgenic TCR be activated by H-2bm13 infected cells in vivo or in vitro. These experiments show that although a TCR may be selected by a mutant MHC molecule, the corresponding viral antigen cannot be recognized in the context of the mutant MHC molecule, as Judged by both negative selection and T cell reactivity in vivo and in vitro. The ‘enhanced' positive selection occurring in the context of Dbm13 suggests that a different conformation of the MHC molecule is able to select the same TCR and also that various TCR-ligand avidities may permit positive selectio

Virological and serological characterization of critically ill patients with COVID-19 in the UK: Interactions of viral load, antibody status and B.1.1.7 variant infection.

BACKGROUND: Convalescent plasma containing neutralising antibody to SARS-CoV-2 is under investigation for COVID-19 treatment. We report diverse virological characteristics of UK intensive care patients enrolled in the Immunoglobulin Domain of the REMAP-CAP randomised controlled trial that potentially influence treatment outcomes. METHODS: SARS-CoV-2 RNA in nasopharyngeal swabs collected pre-treatment was quantified by PCR. Antibody status was determined by spike-protein ELISA. B.1.1.7 was differentiated from other SARS-CoV-2 strains using allele-specific probes or restriction site polymorphism (SfcI) targeting D1118H. RESULTS: Of 1274 subjects, 90% were PCR-positive with viral loads 118-1.7x10 11 IU/ml. Median viral loads were 40-fold higher in those seronegative for IgG antibodies (n=354; 28%) compared to seropositives (n=939; 72%). Frequencies of B.1.1.7 increased from <1% in early November, 2020 to 82% of subjects in January 2021. Seronegative individuals with wild-type SARS-CoV-2 had significantly higher viral loads than seropositives (medians 5.8x10 6 and 2.0 x10 5 IU/ml respectively; p=2x10 -15). However, viral load distributions were elevated in both seronegative and seropositive subjects infected with B.1.1.7 (4.0x10 6 and 1.6x10 6 IU/ml respectively). CONCLUSIONS: High viral loads in seropositive B.1.1.7-infected subjects and resistance to seroconversion indicate less effective clearance by innate and adaptive immune responses. SARS-CoV-2 strain, viral loads and antibody status define subgroups for analysis of treatment efficacy

Estimating the cost of different strategies for measuring farmland biodiversity: Evidence from a Europe-wide field evaluation

Fourty percent of the EU land area is currently considered to be agriculturally managed, and there is growing attention to the environmental performance of farming practices. This involves the need for farm-scale monitoring programmes for sustainability, but their implementation is hampered by a number of difficulties such as the identification of indicators for different latitudes and environments and the evaluation of the effectiveness and costs of different monitoring approaches. In this paper, we focus on the costs of farm-scale biodiversity monitoring, presenting results from a Europe-wide cost data collection in the EU FP7 BioBio Project. Firstly, we propose an analytical assessment of resources consumed by the research units and a cost estimation for the measurement of six biodiversity-related parameters: habitat mapping, vegetation, wild bees and bumblebees, spiders, earthworms and a farm management questionnaire. Thereafter, we estimate a standardised cost for an ordinary measurement of the six parameters at farm-scale. In doing so, we highlight the cost differences between three strategies involving different potential actors (professional agencies, farmers, volunteers). This analysis shows that producing reliable data on monitoring costs requires a large sample pool of farms and farming systems as was the case in the BioBio project. The cost standardisation allows us to estimate the cost range between the different strategies ranging between €2700 and €8200 per far

Functional Deficiency of MHC Class I Enhances LTP and Abolishes LTD in the Nucleus Accumbens of Mice

Major histocompatibility complex class I (MHCI) molecules were recently identified as novel regulators of synaptic plasticity. These molecules are expressed in various brain areas, especially in regions undergoing activity-dependent synaptic plasticity, but their role in the nucleus accumbens (NAc) is unknown. In this study, we investigated the effects of genetic disruption of MHCI function, through deletion of β2-microblobulin, which causes lack of cell surface expression of MHCI. First, we confirmed that MHCI molecules are expressed in the NAc core in wild-type mice. Second, we performed electrophysiological recordings with NAc core slices from wild-type and β2-microglobulin knock-out mice lacking cell surface expression of MHCI. We found that low frequency stimulation induced long-term depression in wild-type but not knock-out mice, whereas high frequency stimulation induced long-term potentiation in both genotypes, with a larger magnitude in knock-out mice. Furthermore, we demonstrated that knock-out mice showed more persistent behavioral sensitization to cocaine, which is a NAc-related behavior. Using this model, we analyzed the density of total AMPA receptors and their subunits GluR1 and GluR2 in the NAc core, by SDS-digested freeze-fracture replica labeling. After repeated cocaine exposure, the density of GluR1 was increased, but there was no change in total AMPA receptors and GluR2 levels in wild-type mice. In contrast, following repeated cocaine exposure, increased densities of total AMPA receptors, GluR1 and GluR2 were observed in knock-out mice. These results indicate that functional deficiency of MHCI enhances synaptic potentiation, induced by electrical and pharmacological stimulation