The Enhancement of MIF Activity by Inhibition of Macrophage Associated Esterases

Abstract

Macrophages pretreated with diisopropyl fluorophosphate (DFP) or incubated with soybean trypsin inhibitor demonstrate enhanced inhibition of migration caused by migration inhibition factor (MIF). This enhancing effect of DFP is time, dose, and temperature dependent. Incubation of MIF in serum treated with DFP had no effect. In addition, hydrolysis products of DFP were inactive. These findings strongly suggest that a macrophage-associated serine esterase, which is present in an active form before the addition of MIF and which counteracts MIF, is involved in the MIF-macrophage interaction. Its significance as a control mechanism in the macrophage-mediator response is discussed.