Immunocytochemical investigations of the membrane of experimentally altered and physiologically aged erythrocytes.

The expression of IgG receptor sites during aging of red blood cells plays an important role in the elimination process of these cells by the Reticulo Histiocytic System. By means of an indirect protein A gold-method, membrane bound IgG was detected immunocytochemically on pronase and neuraminidase treated red blood cells as well as on physiologically aged red cells. The silver enhancement of the gold particles led to an improved labeling of the bound IgG favouring its quantification at both electron and light microscopic level. The result of this gold-silver-technique was analyzed semiquantitatively at the light microscopic level by use of a Vickers scanning microdensitometer. It was shown that the aging of erythrocytes as well as the enzymatic alteration of the erythrocyte glycocalyx by pronase and neuraminidase are accompanied with an unmasking of IgG receptor sites followed by an IgG loading of the cells in presence of autologous serum or plasma. The experimental results, which are presented here indicate that a silver enhancement of gold particles is sufficient to signalize changes in membrane bound ligands at low concentrations.