Interleukin 1 receptor-like 1, also known as IL1RL1 and ST2, is a member of the Toll-like receptor superfamily. The ST2 protein has two isoforms and is 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). ST2 gene expression is related to the growth of cells and that an unknown signal is transduced to control cell proliferation by binding of specific ligand(s). Mutations in this gene have been linked to atopic dermatitis and asthma.