RESUMO
Stilbene 420 dye solution was prepared and the laser dye absorption spectrum was measured. Q-switched frequency-doubling Nd : YAG laser was used as the pumping source to realize the stilbene 420 dye laser and fluorescence spectra analysis. Laser spectroscopy reached the strongest peak at 425 nm and full width at half maximun (FWHM) is 1 nm. Spectral range was from 420 nm to 440 nm. Fluorescence spectrum peak was at 428.5 nm. Compared with the strongest peak laser, the wavelength difference was 3.5 nm. The highest dye conversion efficiency was 9.26%.
RESUMO
The immune system must contend with the billions of cells that are turned over on a daily basis; many of these cells derived from the immune system itself. Recent evidence suggests that the apoptotic cells are processed and presented through classical pathways for MHC II presentation to CD4 T cells and also are cross-presented through a phagosome-cytosolic pathway or released into the cytosol for presentation to CD8 T cells. It appears that the continuous presentation of self-peptides is required for active maintenance of T-cell tolerance. Although for both CD4 and CD8 T cells, anergy is a dominant pathway for tolerance, presentation of self-peptides to CD8 and CD4 T may induce different responses. Phagocytosis of apoptotic cells leads to the production of TGF-beta and/or IL-10 by antigen-presenting cells and there is evidence to suggest that these cytokines favor the generation of CD4 T regulatory cells following encounter with self-antigen. In contrast, CD8 T cells undergo brief activation, an abortive proliferation ultimately leading to reduced long-term survival. The relative quantity and quality of all three signals of TCR engagement, costimulation versus coinhibition and quality of the cytokine response, distinguish T-cell responses to self-versus foreign antigens.