Interaction of Charged Colloids with the RES

Abstract

The involvement of plasma factors in the clearance of colloids from the circulation by the RES has been suggested by many authors, both in a general way [1, 2] and from the point of view of finding specific phagocytosispromoting factors [3]. In the course of our own work, data obtained by the microelectrophoresis of model colloids in serum [4] (see also Table I) would also indicate an interaction between the colloid surface and serum. It has been further suggested that fibrin or fibrin-like macromolecules may be adsorbed on the surface of injected colloids [5], but the involvement of the blood coagulation system in the RES clearance mechanism of colloids has never been firmly established. Circumstantial evidence for this idea comes from several authors. For example, Smith and his co-workers [6] showed that rapid injections of colloidal silica into dogs lowered the fibrinogen content of the blood to less than measurable levels. Biozzi et al. [7], in experiments on blockade, suggested that blood coagulation factors interfered with their measurements but these effects could be reversed by adminstration of heparin. Lee [8] was able to show that fibrin itself produced by slow intravenous infusion thrombin into dogs is cleared by the RES. Finally, it has been shown [9] that calcium ions, known to be essential for blood coagulation, affect phagocytosis in a manner that cannot be explained in terms of its effect on the surface charge of the colloid.