CD80, a costimulatory molecule, plays an important role in eliciting antitumor immunity. Without costimulation, recognition of antigens by T cells may not cause a response, even if tumor cells express MHC class I molecules and specific antigens. On the basis of the recombinant GFP-tagged K b molecule, we constructed a co-expression vector of CD80 and GFP-tagged K b molecules. The recombinant fusion was transfected into mouse melanoma B16 cells by electroporation; positive cells were obtained by G418 screening. Highly expressing monoclonal cells, irradiated by 137 Cs, were used to immunize mice to obtain specific T cells, which were then cultivated with tumor cells in vitro and examined with a laser confocal microscope. The evident and intense uptake of the antigen peptide-MHC class I-GFP complex by specific T cells was visualized from the culture of B16/CD80-K b-GFP and T cells. However, little uptake was observed from the culture of B16/K b-GFP and T cells. These results show that co-expression of CD80 molecules with K b , an MHC class I molecule, on the surface of B16 tumor cells can enhance the response of specific T cells and thus increase the uptake of the antigen peptide-MHC class I-GFP complex. The absorbed green fluorescence was concentrated mainly on the T cell surface, and this result might pave the way to eluting specific antigen peptides directly from T cells to find and isolate novel tumor-specific antigen peptides.
Natural antioxidants could inhibit ROS production and attenuate injury, which is important event of cardiovascular diseases. Water caltrop pericarps from three different Chinese water caltrop cultivars were collected and extracted using 70% methanol and hot water (WCPE). WCPE exhibited strong in vitro antioxidant activities tested by DPPH assay. Incubation with 100μM H2O2 for 1 h would reduce viability of HUVECs to 76.46±0.05%, decrease SOD, CAT and GSH-Px activities to 12.50±0.06, 10.08±0.57 and 107.98±2.68 U/mg protein compared with 20.57±0.02, 22.56±0.41 and 215.28±23.13 U/mg protein of normal cells, increase MDA content from 3.31±0.38 to 9.52±1.87 nmol/mg protein. Pre-treatment, post-treatment and simultaneous with WCPE could attenuate HUVECs injury and recover the viability to 107.77±0.06%, SOD, CAT and GSH-Px activities to 19.11±0.02, 26.14±0.89 and 192.62±7.75 U/mg protein and MDA content to 4.31±0.71 nmol/mg protein. These results suggested that WCPE attenuates H2O2-induced HUVECs injury through promoting proliferation, enhance antioxidant enzymes activities and reduce lipid peroxidation.
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