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Abstract: CTLA-4·Fas ligand (CTLA-4·FasL), a paradigmatic ‘trans signal converter protein (TSCP)’, can attach to APC (via CTLA-4 binding to B7) and direct intercellular inhibitory signals to responding T cells (via FasL binding to Fas receptor), converting an activating APC-to-T cell signal into an inhibitory one. Our previous studies established that CTLA-4·FasL inhibits human primary mixed lymphocyte reactions (MLR) and induces alloantigen-specific hyporesponsiveness ex vivo. The present study extends this to an in vivo context. Using splenocytes from MHC-mismatched C57BL/6 and Balb/c mice, we demonstrated that his6CTLA-4·FasL, effectively inhibits murine MLR. Moving in vivo, we demonstrated that subcutaneously administered his6CTLA-4·FasL modulates the in vivo response of infused allogeneic splenocytes. his6CTLA-4·FasL reduces the number of cells in each cell division, and increases the percentage of dead cells in each division. These findings are consistent with an antigen-induced cell death of the alloreactive cells, and bolsters recombinant TCSP promise as a therapeutic for transplantation diseases. [Copyright &y& Elsevier]

Abstract: Nitrogen resorption efficiency (NRE) and proficiency of 28 plant species belonging to five different life-forms were studied in a semi-arid region of northern China. NRE in these species ranged from 29.8% to 76.1% and averaged about 48.0%, depending upon the species and the life-form. The pattern of NRE in different life-forms followed the order of herbs>shrubs>trees>graminoids>N fixers. Nitrogen resorption proficiency (NRP) ranged from 8.0 to 20.6mgg−1, the average value of which was lowest in graminoids and highest in N fixing species. Leaf-level nitrogen use efficiency (NUE) ranged from 48.5gg−1 to 125.8gg−1, with the average NUE being lowest in the N fixing species and highest in the graminoids. Our findings show that most of the 28 species examined in this study can be categorized as low N-proficiency plants. The lower nitrogen concentration in living tissues and the greater nitrogen resorption during senescence could have contributed jointly to the leaf-level NUE of the species. It was noted that NRP was negatively correlated to NRE, while a positive correlation between the leaf-level NUE and NRE was found for all the species. We had also found a significant positive relation between NRE and the N concentration in green leaves for all the species pulled together, suggesting that green leaf N content might have partially controlled the leaf N resorption. [Copyright &y& Elsevier]