Fibronectin-mediated inhibition of human platelet activation by crosslinked immunoglobulin G.

The effect of purified human plasma fibronectin on stimulation of human platelets with crosslinked immunoglobulin G (IgG) was tested by means of aggregometry, 14C-serotonin release and fibronectin-to-platelet binding experiments. Incremental additions of fibronectin to gel-filtered platelets (8 X 10(8)/ml) followed by 25 micrograms/ml bisdiazoniumbenzidine (BDB)-crosslinked IgG produced a dose-related inhibition of platelet aggregation and suppression of 14C-serotonin release from the platelets. Evidence was obtained that upon stimulation of the platelets with BDB-IgG, fibronectin becomes bound to its receptor and that further platelet activation is inhibited when a sufficient number of receptors is occupied.