ST2 (for growth STimulation expressed gene 2; also known as IL1RL1, or Interleukin 1 Receptor-Like 1) is a member of the interleukin 1 receptor family. Early studies suggested that expression of this receptor can be induced by various stimuli, and may also be involved in the function of helper T-cells.

The ST2 protein has two isoforms directly implicated in the progression of cardiac disease: a soluble form (referred to as soluble ST2 or sST2) and a membrane-bound receptor form (referred to as the ST2 receptor or ST2L). The ligand for ST2 is the cytokine Interleukin-33(IL-33). Binding of IL-33 to the ST2 receptor, in response to cardiac disease or injury, such as an ischemic event, elicits a cardioprotective effect resulting in preserved cardiac function.

This cardioprotective IL-33 signal is counter-balanced by the level of soluble ST2, which binds IL-33 and makes it unavailable to the ST2 receptor for cardioprotective signaling. As a result, the heart is subjected to greater stress in the presence of high levels of soluble ST2, leading to cellular death and tissue fibrosis, reduced cardiac function, and increasing the rate of disease progression.

The Presage® ST2 Assay quantitatively measures the concentration of soluble ST2, providing a physician with an accurate tool to assess prognosis in patients with cardiovascular disease.