Significance of the length of time interval between lethal irradiation and transplantation of haemopoietic cells.

It could be shown that the efficiency of haemopoietic cell transplantation into lethally irradiated mice depended upon the degree of histocompatibility between the donor and the host as well as on the number of transplanted cells. With a prolongation of the time interval between irradiation and transplantation a proportionally higher number of transplanted haemopoietic cells was required to maintain the curative effect of transplantation. The haemopoietic microenvironment in lethally exposed mice remained unchanged until the tenth day after irradiation.