[Fibronectin and fibronectin receptors on the surfaces of polymorphonuclear leukocytes]

Interaction between human neutrophils and fibronectin bound to gelatin-Sepharose granules was studied. It was found that fibronectin following cell-induced dissociation from gelatin-Sepharose caused neutrophil aggregation which was inhibited by EDTA or pretrypsinization of the cells. Besides, polymorphonuclear lymphocytes were found to be capable to adhere to and to spread on gelatin-Sepharose granules. This process was enhanced in the presence of heparin and inhibited by neutrophil pretrypsinization. The conclusion has been drawn on simultaneous existence of fibronectin and fibronectin receptors on the surface of neutrophils. A hypothesis is advanced of the existence in the fibronectin molecule of two independent binding sites, one being responsible for cell attachment and the other for gelatin binding.