INTERLEUKIN-1 TYPE-II RECEPTOR - A DECOY TARGET FOR IL-1 THAT IS REGULATED BY IL-4

Interleukin-1 (IL-1) interacts with cells through two types of binding molecules, IL-1 type I receptor (IL-1R I) and IL-1R II. The function of IL-1R II is unknown. In studies using monoclonal antibodies, IL-1 p rolonged the in vitro survival of polymorphonuclear cells (PMN) throug h IL-1R I, and IL-4 antagonized the action of IL-1 by inducing express ion and release of IL-1R II. Dexamethasone also induced expression and release of the IL-1R II in PMN. These results, together with the effe ct of antibodies to IL-1R on IL-1-induced production of cytokines in m onocytes, indicate that IL-1 acts on myelomonocytic cells through IL-1 R I and that IL-1R II inhibits IL-1 activity by acting as a decoy targ et for IL-1. The existence of multiple pathways of regulation emphasiz es the need for tight control of IL-1 action.