Cyclosporine
Cyclosporine, name of a drug approved for clinical use in the United States in 1983. The drug is important because of its ability to suppress the action of the body's immune system in rejecting foreign tissues following organ transplant operations (see Medical Transplantation ). Specifically, it blocks the activity of certain cells in the immune system called T cells, which, in combination with cells in the bloodstream, would otherwise tend to attack the tissues of the transplanted organs. Operations of this nature have proved successful a great percentage of the time when using cyclosporine. There is some risk of potentially severe kidney damage, however, so care must be taken in administering the drug. Cyclosporine occurs naturally in a certain Norwegian fungus, Tolypocladium inflatum.