Abstract
A test system has been developed which permits the semiquantitative estimation of elimination rates of hemopoietic cells and immunologically competent cells in mixtures of the two cell types. The inactivating effect of storage at 4[degree]C was more pronounced for immunologically competent cells than for hemopoietic cells, selectivity factors of 2.5-10 being obtained. Unequivocal demonstration of selective elimination of this order of magnitude requires elaborate experiments because of the variations inherent in this type of test system.