Due to limited stocks of the IL-2 IS 86/500, a restriction of 3 ampoules per customer per year has been implemented. We would strongly encourage customers to use Non-WHO reference material for IL-2 (86/564) as an alternative where possible until the 3rd WHO IS for IL-2 is established. We advise customers to use the International Standard in compliance with its intended use i.e., to calibrate secondary and/or working standards for use in routine biological assays, when the alternative reagent cannot be used. Replaces 1st International Standard 86/504.