Interphase FISH analysis of sex-mismatched BMT utilizing dual color XY probes

Interphase FISH analysis, utilizing dual color XY probes, was performed on 27 patients following allogeneic sex-mismatched bone marrow transplantation and on 31 controls. Of the 123,167 examined interphase nuclei, 63,318 were from 19 of the 21 patients (54 specimens) who engrafted, 31,827 from five of the six patients (29 specimens) who relapsed (four) or failed to engraft (one) and 24,703 from the 31 control specimens. In patients who engrafted, the mean percentage of host cells was 0.26% between day 29 and 5 years following BMT. Microchimerism of 0.7% or less than 1-5 years following BMT was not predictive of relapse. Interphase FISH analysis predicted relapse or failure of engraftment in five of the six evaluable patients. In three of five patients both conventional cytogenetics and interphase FISH of bone marrow cells provided important information regarding engraftment status and degree of chimerism.