BACKGROUND: Interphase fluorescence in situ hybridization (FISU) analysis following sex-mismatched bone marrow transplantation (BMT) is a sensitive and quantitative method to better assess the engraftment state and mixed chimerism.
METHODS: Twelve patients (allogeneic 11 cases, unrelated 1 case) who underwent sex-mismatched BMT at Chonnam University Hospital from April 1996 through October 1998 were anlaysed chimerism employing FISH. Interphase FISH studies on peripheral blood cytospin slides were performed by using chromosome X α-satellite probe in early post -transplant periods at intervals of 3 days and in follow-up periods 6∼15 months after BMT.
RESULTS: In 11 engrafted patients, the mean percentage of host cells was 3.0% at the period of engraftment (15∼25 days). Follow-up interphase FISH studios for ten patients with hematologic remission states after engraftment showed mixed chimerism with variable degree (mean, 4.7%: ranges, 0.5∼19.0%). Although three of these patients showed host cells above 5.0% (13.2, 8.0 and 7.0%) transiently, they maintained hematologic remission states. One patient who showed 8.5% (344 days) and 14.5% (596 days)
host cells proved to be an engraftment failure.
CONCLUSION: Engrafted patients who obtained hematological remission showed variable mixed chimerism by FISH. When the host cells were low rate or increased transiently, mixed chimerism was not related to relapse. However, consecutive increasing host cells suggested engraftment failure or relapse. More sensitive long term follow-up FISH studies will help to evaluate and monitor engraftment status and degree of chimerism.

Keywords: Bone marrow transplantation, FISH, Engraftment, Mixed chimerism