Binding of plasma fibronectin to human polymorphonuclear leukocytes in normal subjects and patients with aplastic...

The binding of iodine 125-labeled fibronectin to polymorphonuclear leukocytes (PMNs) from human peripheral blood was examined. The optimum temperature and time for the binding were 37 degrees C and 30 minutes, respectively. On increase in the amount of 125I-labeled fibronectin, its binding to PMNs became saturated. Scatchard analysis of data on binding indicated the presence of a single class of binding sites. PMNs from 15 normal subjects had approximately 6.3 +/- 1.6 x 10(3) sites per cell and a dissociation constant of 10.2 +/- 2.4 x 10(-9) mol/L, indicating that they had high affinity for soluble fibronectin. Arg-Gly-Asp-Ser inhibited the binding of fibronectin to PMNs, strongly suggesting that the fibronectin receptor is one of the Arg-Gly-Asp receptor family. The plasma level of fibronectin was higher in patients with hyperthyroidism and lower in patients with hypothyroidism than in normal subjects, without any significant change in the number of fibronectin binding sites of the PMNs. However, the number of binding sites of fibronectin on PMNs of patients with aplastic anemia was increased, probably because of sensitization of the PMNs with immune complex and other factors.