Mixed chimerism after sex-mismatched allogeneic BMT: evaluation of two molecular techniques

Two different molecular techniques were used to monitor chimerism following 17 non-T cell-depleted BMTs from female donors to male recipients: pHY10, a Y chromosome-specific probe (Southern or slot blots), and a set of primers for Y chromosome sequence-specific amplification by the polymerase chain reaction (PCR). On Southern blots, male DNA was detectable at a level less than 1% of 10 micrograms DNA while cross-reactivity with autosomal sequences was avoided. On slot blots, male DNA was reliably detectable at levels less than 0.5%, even in small sample (0.5 microgram DNA). With the PCR technique, male DNA was detectable at levels of 1:10(6) to 1:10(7) of 0.5 microgram DNA. Slot blot and PCR results were concordant in 19 of 23 samples. Both techniques demonstrated a constant small mixed chimerism during the first year after BMT and in four of nine patients, this chimerism persisted even longer (up to 29 months after BMT).