Red cell age and susceptibility to immune haemolysis.

Light and dense human red cell fractions were prepared by ultracentrifugation using isotonic low molecular weight dextran solutions, and tested in a in vitro complement dependent haemolytic system with a rabbit anti-human-red-cell serum (as amboceptor). A second series of experiments was performed with whole blood samples in which the young cells were labelled with 59Fe. The results indicate that young cells are relatively more resistant and old cells more susceptible to immune haemolysis than the whole cell population.