Potentiation of the macrophage response to migration inhibition factor from fetal calf serum by blood group substances with human H activity.

Soluble blood group substances, with human H and A activity, have previously been shown to block the interaction between guinea pig peritoneal macrophages and migration inhibition factor from fetal calf serum (FCS-MIF). Conversely, incubation of macrophages at 37 degrees C for 1 h in the presence of 0.1% blood group substance, followed by thorough washing, potentiates the action of FCS-MIF. The sensitivity of the macrophages is markedly increased, allowing detection of subthreshold levels of FCS-MIF. Blood group substances (BGS) labeled with radioidine are taken up by macrophages, and a proportion remains on the surface. This radiolabeled BGS is lost from the surface spontaneously, and the rate of loss is increased by treatment with trypsin. It is suggested that the BGS mimic the natural macrophage receptor for FCS-MIF and potentiate its effect by incorporating new receptors into the macrophage membrane.