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S. Masli, B. Turpie; Thrombospondin Derived From TGFß-Treated Antigen Presenting Cells Contributes to Regulatory Phenotype of Effectors. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5205.
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: Effector T cells with regulatory phenotype (Treg) are known to mediate immune deviation induced by TGFß-exposed antigen presenting cells (APCs) that resemble eye-derived APCs. These APCs up-regulate their expression of thrombospondin (TSP1) in response to TGFß, which is essential for their ability to induce immune deviation. We now examine the contribution of thrombospondin to the generation of Treg.
: Thioglycollate-elicited peritoneal exudates cells (PECs) from C57BL/6 (Wild-type) or TSP1null mice were used as APCs. These cells pulsed with ovalbumin were cultured overnight in the presence or absence of TGFß (5 ng/ml) and after washing with fresh medium were co-cultured with carboxyfluorescein succinimidyl ester (CFSE)-labeled T cells from OT-II mice. Culture supernatants were collected at 48 hr and analyzed for the presence of IFN-γ, IL-17 and IL-6 in ELISA assays and proliferation profile of T cells was was analyzed by flow cytometry. Total TGFß in the culture supernatant was measured by TGFß bioassay suing MvLu epithelial cell line.
: T cells cultured with wild-type APCs treated with or without TGFß revealed a similar number of cell divisions in both cultures as determined from their CFSE proliferation profile. However, overall T cells cultured with TGFß-treated APCs showed lowered proliferation as compared to those cultured with untreated APCs. Such lowered proliferation was not detected when APCs were deficient in TSP1. T cells cultured with TGFß-treated wild-type APCs secreted significantly decreased levels of IFNγ, IL-17 and IL-6 and increased levels of total TGFß as compared to those cultured with untreated wild-type APCs. The decreased IFNγ synthesis and increased TGFß secretion is consistent with previously described phenotype of Treg generated in vitro as well as in vivo. On the other hand TGFß-treated TSP1 deficient APCs although induced decreased levels of IFNγ, IL-17 and IL-6 as compared to the levels induced by untreated TSP1 deficient APCs, they failed to increase total TGFß secretion of T cells. These results are consistent with the failure of TSP1 deficient APCs to suppress delayed type hypersensitivity (DTH) response upon their exposure to TGFß.
: Increased synthesis of TSP1 by TGFß-treated APCs directs the phenotype of responding effectors towards regulatory type by promoting their TGFß secretion. Our results indicate a significant contribution of TSP1 to the generation of regulatory T cells involved in immune deviation induced by TGFß-treated APCs.
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