IN VITRO IMMUNOSUPPRESSIVE PROPERTIES OF CYCLOSPORINE... : Transplantation (original) (raw)

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Transplantation Immunology Laboratory, Department of Surgery, Albany Medical College, Albany, New York 12208, and Departments of Clinical Chemistry and Biochemistry, Albany Medical Center Hospital and Albany Medical College, Albany, New York 12208

3,4 Departments of Clinical Chemistry and Biochemistry.

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Abstract

The in vitro biological activity of cyclosporine (CsA) and four of its metabolites (M1, M8, M17, and M21) was determined. M1, M17, and M21 are primary metabolites, while M8 is a secondary metabolite derived from either M1 or M17. The order of inhibitory activity in production assays was phytohemagglutinin (PHA), con-canavalin A (ConA), mixed lymphocyte culture (MLC), and interleukin-2 (IL-2) CsA > M17 > M1 > M21 “ M8. In the PHA assay, CsA was significantly more inhibitory than M17, but in Con A and MLC assays, the inhibitory activity of M17 approached that of CsA. More importantly, M17 and Ml inhibited the production of IL-2 in the MLC to the same extent as CsA. M21 was significantly less inhibitory than either M17 or M1, and M8 appeared to be largely devoid of biological activity. These experiments demonstrate that single hydroxylations of amino acids 1 (M17) and 9 (M1) do not significantly affect the ability of the molecule to block IL-2 production, but hydroxylation of both amino acids renders the molecule virtually inactive. In addition, the presence of the N-methyl group on amino acid 4 appears to be very important, since removal of this group (M21) greatly diminishes the immunosuppressive activity.