RESUMO
Migratory waterfowl vector plant seeds and other tissues, but little attention has focused on the potential of avian vectoring of plant pathogens. Extensive meadows of eelgrass (Zostera marina) in southwest Alaska support hundreds of thousands of waterfowl during fall migration and may be susceptible to plant pathogens. We recovered DNA of organisms pathogenic to eelgrass from environmental samples and in the cloacal contents of eight of nine waterfowl species that annually migrate along the Pacific coast of North America and Asia. Coupled with a signal of asymmetrical gene flow of eelgrass running counter to that expected from oceanic and coastal currents between Large Marine Ecosystems, this evidence suggests waterfowl are vectors of eelgrass pathogens.
RESUMO
INTRODUCTION: It has been previously shown that immunoregulatory DX5+NKT cells are able to prevent colitis induced by CD4+CD62Lhigh T lymphocytes in a SCID mouse model. The aim of this study was to further investigate the underlying mechanism in vitro. METHODS: CD4+CD62Lhigh and DX5+NKT cells from the spleen of Balb/c mice were isolated first by MACS, followed by FACS sorting and cocultured for up to 96 h. After polyclonal stimulation with anti-CD3, anti-CD28, and IL-2, proliferation of CD4+CD62Lhigh cells was assessed using a CFSE assay and activity of proapoptotic caspase-3 was determined by intracellular staining and flow cytometry. Extrinsic apoptotic pathway was blocked using an unconjugated antibody against FasL, and activation of caspase-3 was measured. RESULTS: As previously shown in vivo, DX5+NKT cells inhibit proliferation of CD4+CD62Lhigh cells in vitro after 96 h coculture compared to a CD4+CD62Lhigh monoculture (proliferation index: 1.39 ± 0.07 vs. 1.76 ± 0.12; P = 0.0079). The antiproliferative effect of DX5+NKT cells was likely due to an induction of apoptosis in CD4+CD62Lhigh cells as evidenced by increased activation of the proapoptotic caspase-3 after 48 h (38 ± 3% vs. 28 ± 3%; P = 0.0451). Furthermore, DX5+NKT cells after polyclonal stimulation showed an upregulation of FasL on their cell surface (15 ± 2% vs. 2 ± 1%; P = 0.0286). Finally, FasL was blocked on DX5+NKT cells, and therefore, the extrinsic apoptotic pathway abrogated the activation of caspase-3 in CD4+CD62Lhigh cells. CONCLUSION: Collectively, these data confirmed that DX5+NKT cells inhibit proliferation of colitis-inducing CD4+CD62Lhigh cells by induction of apoptosis. Furthermore, DX5+NKT cells likely mediate their cytotoxic and proapoptotic potentials via FasL, confirming recent reports about iNKT cells. Further studies will be necessary to evaluate the therapeutical potential of these immunoregulatory cells in patients with colitis.
