Fibronectin-mediated uptake of gelatin-coated latex particles by peritoneal macrophages.

Abstract

Plasma fibronectin or cold-insoluble globulin (Clg) can promote the uptake of 125I-labeled, gelatin-coated latex beads (g-Ltx) by monolayers of [rat] peritoneal macrophages (PM). The uptake of g-Ltx by PM was enhanced by Clg in a concentration-dependent fashion and required the presence of heparin (10 U/ml) as an obligatory cofactor for maximal particle uptake. Treatment of PM monolayers with trypsin (1 mg/ml) for 15 min at 37.degree. C after particle uptake removed < 15% of the radioactivity incorporated by the monolayers. A similar trypsin treatment of the monolayers before the addition of latex particles depressed Clg-dependent uptake by > 75%. Pretreatment of PM monolayers with inhibitors of glycolysis effectively reduced the Clg-dependent uptake of latex. Similarly, pretreatment of monolayers with either inhibitors of protein synthesis or agents that disrupt cytoskeletal elements also significantly depressed Clg-dependent particle uptake. Phagocytosis of g-Ltx by PM in the presence of Clg and heparin was confirmed by EM. G-Ltx could also be effectively opsonized with Clg at 37.degree. C before their addition to the monolayers. The recognition of g-Ltx in the presence of Clg required cell surface protein(s) and that subsequent phagocytosis of these particles by PM was energy dependent and required intact intracellular cytoskeleton elements. PM monolayers provide a suitable system for further studies on the function of Clg in the recognition and phagocytosis of gelatin-coated particles by phagocytic cells.