Detection of Mixed Chimerism after Sex-Mismatched Bone Marrow Transplantation Using Fluorescence in situ Hybridization: Engraftment and Follow-up Evaluation

Ryang, Dong Wook; Hong, Won Pyo; Cho, Deok; Lee, Je Jung; Chung, Ik Joo; Cho, Moon Kee; Kook, Hoon; Hwang, Tai Ju; Shin, Jong Hee; Suh, Soon Pal

Abstract

BACKGROUND
Interphase fluorescence in situ hybridization (FISH) 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 alpha-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 studies 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 engraftement 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.