ABSTRACT
T cell activation is a critical event for initiation and regulation of immune responses and inhibitors of such signaling pathways are clinically useful for the treatment of patients received allogratt and autoimmune disease. In the course of screening soil microorganisms from the forest of Cheju island in Korea for new immunosuppressive agent, one of Streptomyces species (CK-95441) was found to produce a new immunosuppressant, tautomycetin which also had antifungal activity. Tautomycetin showed the inhibition of T cell proliferation in murine mixed lymphocyte reaction (MLR) and T cell activation induced by concanavalin A. Tautomycetin also blocked the induction of IL-2 gene expression which was examined in Jurkat TAg cell line in which multiple NFAT-binding sites and minimal IL-2 promoter drive the production of B-galactosidase. Also, the level of inhibition in activation-induced IL-2 receptor expression by tautomycetin was greater than those by cyclosporin A measured by flow cytometry. But, Fas ligand-induced apoptosis in Jurkat cells was unaffected by tautomycetin which was measured by DNA fragmentation assay. These results suggested that tautomycetin will be able to be used as a potent immunosuppressive drug following organ transplantation.
ABSTRACT
The systematic study of products from bacteria and fungi has led to the development of two immunosuppressive drugs, cyclosporin A and FK 506 (tacrolimus) which are useful to suppress adaptive immune responses to the grafted tissue. However, they affect all immune responses indiscriminately and are both toxic to kidneys and other organs. To facilitate the development of immunosuppressor to block the T cell receptor (TcR)-mediated signaling cascade specifically, a novel Jurkat T cell transfectants, JK NFAT-SEAP were generated in which the expression of the secreted alkaline phosphatase (SEAP) is driven by the multiple NFAT binding sites plus minimal IL-2 promoter. Upon stimulation with ionomycin or anti-TcR mAb OKT3 in the presence of PMA, these transfectants secreted high level of SEAP into the medium, which was conveniently analyzed by SEAP analysis. The secretion of SEAP was effectively inhibited by cyclosporin A or FK 506 at the concentration of [10 ' ug/ml], [10 ug/ml] respectively. JK NFAT-SEAP transfectants will provide two major advantages for the development of a novel immunosuppressor. First, analysis of SEAP secreted into the culture medium by SEAP analysis enables us to test a large number of samples within a short period of time. Second, Usage of IL-2 promoter for the expression of SEAP makes us identify bioproducts to target specifically on TcR-mediated signaling pathway.