Inhibition of polymorphonuclear leukocyte chemotaxis byα-macrofetoprotein, an acute-phase reactant of the rat

Abstract
α-Macrofetoprotein (αMFP) is a normal fetal plasma constituent in the rat, with very low plasma levels in the adult phase but rising sharply after injury. This fetal acute-phase protein is a strong inhibitor of inflammatory edema. Fetal inflammatory reactions show diminished exudation, but also impaired emigration of polymorph nuclear cells (PMNs). Therefore we studied the effect of (αMFP on chemotaxis of PMN in vitro and in vivo. In vitro experiments showed a strong inhibitory effect on casein-induced leukotaxis (Boyden technique) with a clear dose-effect relationship. In vivo with glycogen-induced pleurisy and peritonitis, high (αMFP levels are accompanied by diminished PMN emigration and vice versa. The significance of these findings is discussed in relation to fetal pathology and also as a model showing the modulating effects of acute-phase proteins on the inflammatory reaction induced by tissue injury.