Effect of plasma fibronectin on the adhesive properties of human peripheral lymphocytes.

The adhesive properties of human peripheral lymphocytes (HPL) towards immunobilized substrate in vitro have been investigated. The role of plasma fibronectin was studied in two different systems: a) immobilized fibronectin as a model of cell adhesion in the tissues; b) soluble fibronectin as a model for cell adhesion in blood circulation. Collagen (Type I) or collagen-fibronectin-coated surfaces were used as substrate for lymphocyte adhesion in system b. A very small amount of HPL (5.1 +/- 1.2%) was attached to the collagen surface. The adhesion to fibronectin or to collagen-fibronectin surfaces, however, was substantially higher, reaching a value of 34.1 +/- 3.8% and 32.7 +/- 5.8%, respectively. The addition of soluble fibronectin to system a leads to a competitive inhibition of adhesion. On the contrary, in the presence of soluble fibronectin, the augmentation of the lymphocyte adhesion to collagen was found to be dose-dependent and nearly 4 times higher as compared to the control level. This effect was found to be maximal at fibronectin concentrations of 250-300 micrograms/ml. The data demonstrate the important role of plasma fibronectin in the adhesive interactions of lymphocytes.