Displacement bone marrow transplantation for some inborn errors.

The initial simple bone marrow transplants for genetic immunodeficiency diseases could hardly be rejected by the host, but required matched sibling donors, only available for about 1 in 5 patients. Improved inductions enabled alternative donors from the family or unrelated volunteers to be used. Measurement of the extent of engraftment by donor cell markers or their normal enzymes showed the need for displacement, which aims to obtain 100% donor-type marrow so that the future immune responses of the recipient become those of the donor and tolerant to donor cells or their products. Immunoprophylaxis can prevent residual host immune cells from surviving to impair the graft. The concept of DBMT with immunoprophylaxis has evolved either to replace abnormal host cells or to confer a component transferable from donor cells to deficient host tissues. Within 10 years over 40 previously fatal genetic diseases have been satisfactorily corrected and seven partially corrected, but for five there has been inadequate delivery of component to genetically defective tissues such as heart, cartilage and brain. The principles can be applied to some 40 other genetic diseases for which no suitable alternative treatments yet exist.