ABSTRACT
The selective recognition of senescent cells cannot be compared with the binding of a hormone to its receptor, since cell elimination is in all cases a cooperative phenomenon mediated by several weakly interacting components rather than one high affinity binding event. Bivalent binding of naturally occurring antibodies to cell surfaces requires the cell to provide antigen oligomers. The tissue homeostatic mechanisms operating in the elimination of erythrocytes may serve as a paradigm for other types of cell eliminations, since cellular modifications can best be studied on anucleated erythrocytes. Multicellular organisms that live longer than some of their tissue cells eliminate senescent cells and replace them by the progeny of stem cells. Mammalian erythrocytes, so far, are the best model system to study cell aging, since cellular aging phenomena are not perturbed by ongoing protein synthesis. The hypertransfusion experiments and the survival studies with biotinylated cells further allowed the researchers to define the modifications that characterize membranes of senescent erythrocytes.
