Comparison of nucleated and enucleated asialylated erythrocytes' survival time.Possible role of T-agglutinin

Immune elimination of aging platelets by autologous monocytes: role of membrane-specific autoantibody

Membrane-bound IgG was found only on old populations of platelets from normal individuals. This IgG could be dissociated from senescent cells by repeatedly heating the cells. Heat-eluted IgG (He-IgG) prepared from senescent red blood cells was capable of binding to either heat-treated old platelets or Vibrio cholerae neuraminidase (VCN)-treated young platelets, suggesting expression of a common age-dependent antigen on the senescent red blood cells and old platelets. We analyzed the role of membrane-bound IgG in the immune elimination of aging platelets by direct phagocytosis of different platelet subpopulations by autologous monocytes in vitro. While removal of He-IgG from old platelets inhibited their phagocytosis, preincubation of either heat-treated old or VCN-treated young platelets promoted phagocytosis of these cells by autologous monocytes. The phagocytosis of senescent cells required intact IgG on these cells. Either removal of Fc fragments from He-IgG or treatment of autologous monocytes with Fc fragments prior to the phagocytosis assay resulted in a marked reduction of phagocytosis (greater than 75%). We conclude that Fc receptors on the monocytes and the presence of membrane-specific IgG are crucial elements for immune elimination of senescent platelets.

Phagocytosis of senescent erythrocytes by autologous monocytes: requirement of membrane-specific autologous IgG for immune elimination of aging red blood cells

The role of membrane-bound IgG present on the membrane of senescent erythrocytes in immune eliminations of aging red cells was investigated. Phagocytosis of populations of red blood cells (RBC) of different ages by autologous monocytes was assessed both by direct phagocytosis and by induction of microsomal heme oxygenase. Removal of IgG from older RBCs inhibited their phagocytosis; in contrast, preincubation of neuraminidase-treated young or in vitro aged RBCs with IgG eluted from old cells led to phagocytosis of RBCs treated by autologous monocytes. It was also found that the Fc portion of membrane-bound IgG is essential for the elimination of senescent cells; less than 15% of old heat-inactivated RBCs coated with F(ab)2 fragment of membrane-bound IgG were phagocytosed. In contrast, more than 50% of old heat-inactivated RBCs coated with heat-eluted IgG were phagocytosed by autologous monocytes. A possible mechanism of elimination of aged cells is discussed.

Individual variations of the seven carbohydrate components of human erythrocyte membrane during aging in vivo

The contents of fucose, mannose, galactose, glucose, 2-acetamido-2-deoxy-D-glucose and -D-galactose, and sialic acid, when the results were expressed as nmol per mg of membrane dry-weights, were found to be significantly lower in the membranes of old erythrocytes than in the membranes of young ones. No significant difference was found between young and old membranes when the compositions were expressed as residues per one hundred carbohydrate residues, suggesting that a homogeneous decrease of the carbohydrate moieties may occur during aging in vivo.