Seung Goo Kang

We propose and demonstrate a novel wavelength-division-multiplexing (WDM) source employing an uncooled and unisolated Fabry-Perot semiconductor laser diode (F-P SLD). The output wavelength of F-P SLD is locked to the externally injected narrow-band amplified spontaneous emission (ASE). The measured side-mode suppression ratio of the wavelength-locked F-P SLD is larger than 29 dB, when the extinction ratio of the directly modulated light output is above 13 dB. We achieved error-free transmission of 155-Mb/s data over 120 km of nondispersion-shifted fiber. We also propose a cost-effective WDM passive optical network architecture based on the proposed light sources.

In this study, we report a novel biological function of vitamin A metabolites in conversion of naive FoxP3- CD4+ T cells into a unique FoxP3+ regulatory T cell subset (termed "retinoid-induced FoxP3+ T cells") in both human and mouse T cells. We found that the major vitamin A metabolite all-trans-retinoic acid induces histone acetylation at the FoxP3 gene promoter and expression of the FoxP3 protein in CD4+ T cells. The induction of retinoid-induced FoxP3+ T cells is mediated by the nuclear retinoic acid receptor alpha and involves T cell activation driven by mucosal dendritic cells and costimulation through CD28. Retinoic acid can promote TGF-beta1-dependent generation of FoxP3+ regulatory T cells but decrease the TGF-beta1- and IL-6-dependent generation of inflammatory Th17 cells in mouse T cells. Retinoid-induced FoxP3+ T cells can efficiently suppress target cells and, thus, have a regulatory function typical for FoxP3+ T cells. A unique cellular feature of these regulatory T cells is their high expression of gut-homing receptors that are important for migration to the mucosal tissues particularly the small intestine. Taken together, these results identify retinoids as positive regulatory factors for generation of gut-homing FoxP3+ T cells.