Engraftment monitoring occurs after a bone marrow transplant (BMT) and detects the level of donor DNA and donor cells versus recipient DNA and recpient cells post transplant to determine chimerism and if the transplant was successful or is failing.
Engraftment studying can be performed on bone marrow and/or peripheral blood after transplant. Engraftment monitoring takes advantage of known allelic differences between recipient and donor microsatellites, also known as short tandem repeats [STRs], which are repeating oligonucleotides, ranging from 2-7 base pairs in length and can be considered "unique." There are commercially available kits that have redudnant sequence found within the human genome as indicated in the figure below. These STRs are found on autosomal and sex chromosomes and are unique to each person (STRs may be identical in monozygotic twins as they share 100% of their genome)
This technology is also used for paternity testing and crime investigations, as it provides unique information (like fingerprints) and is rich in microsatellites.
Engraftment monitoring can be performed on buccal, peripheral blood, bone marrow, or hair follicles samples.
To determine chimerism, donor and patient STR profiles are typically assessed before transplantation of bone marrow to determine which STR peaks belong to which person. In a patient with a successful bone marrow transplant, only donor STRs would be showing up in blood and bone marrow samples. This implies the graft is performing hematopoiesis within the bone marrow and has not been recognized as foreign by the host's immune system. HLA genotype matching helps to increase odds of BMT success.