Interleukin 1 receptors and biological responses.

Interleukin 1 (IL-1) is a polypeptide which possesses a wide variety of biological properties. IL-1 was originally studied as "endogenous pyrogen" and "leukocytic endogenous mediator" and more recently as "lymphocyte activating factor." Within a few minutes after intravenous injection into experimental animals, IL-1 triggers events in the hypothalamus to initiate fever, slow-wave sleep, and the release of a variety of neuropeptides. The nature of the IL-1 receptors (IL-1R) is important to the understanding of IL-1's multiple action in mediating both neural and non-neural events. In this paper, the data are reviewed on the physical nature of the dominant, high-binding 80 kDa IL-1R isolated from murine T cells. In addition, newer studies demonstrate the existence of other IL-1 binding proteins which may participate as functional IL-1 receptors. These are a 68-75 kDa binding protein found on B cells and a 26-30 kDa binding protein found on T cells and mesangial cells. There is a considerable discrepancy between the number and affinities of the 80 kDa IL-1R and biological responses. Little is known about the relationship of the 68-75 or 26-30 kDa IL-R's biological responses. It is possible that, similar to neurotransmitter receptors, multiple chains of different binding proteins participate in the signal transduction of IL-1. The hydrolysis of non-phosphatidyl inositol membrane phospholipids plays an important role in responses to IL-1.