Quantification of fluorescent STR genotyping results for chimerism control after bone marrow transplantation

1. IntroductionEngraftment of donor stem cells after allogeneic bone marrow transplantation can begenetically monitored by PCR typing of DNA polymorphisms [1]. Successful engraftmentwith complete chimerism and presence of the donor’s genotype in the bone marrow has tobe demonstrated, and the presence of the patient’s alleles has to be excluded. Detection ofthe patient’s alleles provides evidence for an incomplete chimerism or for a relapse ofmalignant disease. STRs have been used successfully for this type of genetic monitoring[2]. For the present study, we have developed an approach to quantify the ratio of donorchimerism using mock mixture experiments. The usefulness of our approach is demon-strated in typical cases where the donor chimerism could be monitored over periods ofmore than 1 year after transplantation (Tx).2. MethodsThe degree of donor–recipient chimerism was monitored by a semi-quantitativeanalysis of the mixed STR genotypes. DNA was extracted from bone marrow samplesas well as from FACS-separated mononuclear cells, CD3+ T cells and CD3 mono-nuclear cells. Furthermore, buccal swabs were collected from donor and recipient toestablish their genotypes prior to transplantation. The DNA was subjected to PCR typing