T1/ST2 is a receptor-like molecule homologous to the type I interleuki
n-1 receptor. Despite this sequence similarity, me have been unable to
demonstrate binding of T1/ST2 to any of the three interleukin-1 speci
es. In searching for a ligand for T1/ST2, we have cloned a cell surfac
e protein to which it binds. This protein is unable to initiate signal
transduction by the T1/ST2 receptor in several in vitro assays.