Bone marrow transplantation for severe combined immune deficiency in an infant with chimerism due to intrauterine-derived maternal lymphocytes: donor engraftment documented by chromosomal marker studies.

Chromosomal heteromorphisms defined by the quinacrine banding technique were used to identify the maternal origin of 46,XX lymphocytes present in the blood of a male infant with severe combined immune deficiency disease. These chromosomal markers were also used to document the engraftment by donor lymphocytes from the sister and the concurrent disappearance of maternal lymphocytes after a successful bone marrow transplantation. Donor lymphocytes were detected by this technique 6 days after transplantation, earlier than is usually possible with other marker systems and before definite evidence of immunoreconstitution. Maternal lymphocytes persisted in the patient's peripheral blood for a prolonged period of time, being detectable 172 days after transplantation. Analysis of T-lymphocyte- and B-lymphocyte-enriched populations after transplantation documented lymphoid chimerism with T-lymphocytes of donor origin and B-lymphocytes of both patient and donor origin, demonstrating prolonged persistence of patient B-lymphocytes and suggesting that the patient's immune defect is primarily at the T-lymphocyte level.