Fibronectin-enhanced attachment of gelatin-coated erythrocytes to isolated hepatic Kupffer cells

The phagocytic process is a combination of a sequence of events which includes a recognition attachment phase and a subsequent internalization phase. The present study was designed to investigate the effect of plasma fibronectin on the attachment and ingestion of gelatinized sheep erythrocytes to isolated rat Kupffer cells in a monolayer assay. Kupffer cells were isolated by sequential collagenase-pronase digestion followed by metrizamide density gradient centrifugation and subsequent adherence to plastic. Classification as Kupffer cells was confirmed by the presence of functional Fc receptors, a positive peroxidase reaction, and phagocytic activity. Purified plasma fibronectin as well as rat serum containing fibronectin promoted attachment of gelatinized fixed sheep erythrocytes to Kupffer cells in a dose-dependent manner, whereas fibronectin-deficient serum did not. Heparin did not enhance the fibronectin-mediated attachment or ingestion of gelatinized sheep erythrocytes at lower particle doses, whereas at higher particle doses heparin augmented the response. These results indicate that fibronectin can enhance the binding and ingestion of foreign gelatin-coated particulates by Kupffer cells.