Mechanisms for the removal of senescent human erythrocytes from circulation: specificity of the membrane-bound immunoglobulin G.

Direct antiglobulin (Coombs') tests of erythrocyte (RBC) subpopulations confirmed the presence of membrane-bound immunoglobulin G (IgG) on old (density greater than 1.110) human RBCs but not on the young (density less than 1.110) RBCs. After thermal elution of the bound IgG, this Coombs' reaction was negative, but incubation of thermally eluted IgG (He-IgG) with heat-treated RBCs induced a positive antiglobulin test. A positive direct antiglobulin reaction was also obtained after incubation of heat-treated RBCs with anti-T antibody. Similar results were obtained when young RBCs treated with Vibrio cholerae neuraminidase (VCN) were incubated with anti-T or with IgG eluted by heat from old RBCs. Nevertheless, pre-absorption of heat-eluted IgG with T and/or Tn antigen, did not prevent it from binding to either heat-treated old or VCN-treated young RBCs as assessed by the antiglobulin consumption assay. Pre-treatment of either VCN-treated young or heat-treated old RBCs with anti-T and/or anti-Tn antibodies had no significant effect on the binding of radiolabeled He-IgG (eluted from old RBCs). The results indicate that even though desialylation of the erythrocyte membrane is required for binding of both anti-T-Tn and He-IgG, the specificity and consequently the RBC binding sites for He-IgG and anti-T seem to be different.