in 1969, stähelin made the key decision to include a test system for immunosuppression into the general screening program at sandoz for compounds and extracts. he invented a new procedure which permitted the use of the same mice for testing both anticancer activity (l-1210) and immunosuppression (inhibition of antibody formation) in an "all in one "in-vivo" test system". this considerably reduced both the number of experimental animals and the quantity of test substances required, and also decreased the labour involved. stähelin's invention of this procedure initiated an innovative screening system for discovering immunosuppressant drugs lacking bone marrow toxicity – the first such screen to be discovered. this screening process was first used in the pharmacology department in january 1970, before jean f. borel joined stähelin's group.