Combined use of immunocytochemical techniques and ligand‐gold complexes for investigation of platelet membrane responses to surface activation

Exposure of blood platelets to foreign surfaces results in dramatic changes in physical appearance and conversion from a non-sticky to an adhesive state. Membrane glycoproteins and cytoskeletal assembly play a pivotal role in these interactions. Cytochemical techniques commonly applied for demonstration of macromolecules in tissues have been used for the localization of target glycoproteins on spread cells. The present review examines different experimental strategies and immunocytochemical techniques that can be combined to better understand the organization of platelet receptors during surface activation. Glycoprotein IIb-IIIa (GPIIb-IIIa) was localized by immunocytochemical techniques on fixed, surface-activated platelets. The distribution of functional fibrinogen receptors expressed on GPIIb-IIIa was revealed by incubation of fixed platelets with fibrinogen-gold conjugates (Fgn/Au). The movement of receptor complexes was investigated in additional experiments in which surface-activated platelets were interacted with Fgn/Au and then fixed at different periods. The overall impression of these observations suggests that fibrinogen receptors on surface-activated platelets do not redistribute spontaneously and that particulates (gold particles), rather than fibrinogen, may trigger the movement. These results are presented in detail and their significance discussed in the light of current theory. Applications and limitations of such techniques are also discussed.