Trans­fer­ring stem cells taken from the bone mar­row of a healt­hy donor to a pati­ent. This is only pos­si­ble if the HLA tis­sue cha­rac­te­ris­tics match. The patient’s bone mar­row is des­troy­ed by che­mo­the­ra­py (fre­quent­ly com­bi­ned with irra­dia­ti­on) one week befo­re­hand. At the same time, the immu­ne sys­tem is sup­pres­sed to pre­vent trans­plant rejec­tions. After this tre­at­ment, the pati­ent will have no immu­ne reser­ves and will not sur­vi­ve without the dona­ted stem cells.