Stimulation of Rat Macrophage Interleukin 1 Secretion by Plasma Fibronectin

Abstract

Purified plasma fibronectin (Fn) enhanced the secretory activity of rat peritoneal exudate macrophages as measured by ³⁵S-methionine incorporation into protein released into culture supernatants. Enhancement of protein secretion was dose-dependent and increased with time in culture. Addition of various concentrations of supernatant from cultures of macrophages with Fn resulted in a significant increase in thymocyte proliferation elicited by phytohaemaglutinin. The stimulatory activity of the supernatant was Fn dose-dependent and increased with increasing concentrations of macrophages. This thymocyte stimulatory effect was not due to the presence of Fn in the culture supernatant or to the minimal contamination with endotoxin detected in the Fn preparations. These data suggest that the inflammatory macrophage interaction with Fn results in the release of interleukin-1. They also are consistent with the reported ability of Fn to stimulate lymphocyte transformation.