The experimental and clinical background in low-dose IL-2 therapy suggests a potential clinical utility of Treg cell expansion in patients with ACS. Administration of low doses of IL-2 in various clinical settings appears to be safe and remarkably efficacious at promoting selective expansion of Treg cells with preserved suppressive function. This is the first trial to assess the mechanism of action of IL-2 therapy in cardiovascular patients. The aim of Part A of this clinical trial is to assess the safety of low-dose IL-2 as well as the proof of mechanism in patients with stable ischaemic heart disease. Part B aims to assess the safety and efficacy of, and increase in Treg as a result of this drug supplementation, in the setting of ACS.