Short-term study of chimaerism after bone marrow transplantation for severe aplastic anaemia

Chimaerism was studied early (2 weeks to 3 months) during haematopoietic reconstitution after bone marrow transplantation in 18 severe aplastic anaemia patients (acquired SAA: 14 patients; Fanconi anaemia: four patients). Fourteen patients received marrow from an identical sibling donor, one from the phenoidentical father and three from a matched unrelated donor. Peripheral blood cell DNA was first analysed by Southern blotting with a multilocus minisatellite probe (33.6.3) or a Y chromosome specific probe (pHY2.1). For all 14 patients grafted with a genotypically identical sibling donor, the post-graft DNA profile strictly matched the respective donor profile (minisatellite probe) or disclosed the Y chromosome specific band in the case of female patients grafted with a male donor. In contrast, for the one patient grafted in a mismatched situation and for two out of three patients grafted with a matched unrelated donor, the results indicated autologous bone marrow recovery. This difference between patients grafted with an identical sibling donor and those grafted in other situations is statistically significant (P less than 0.01). The 15 patients with circulating cells of donor origin were then studied by polymerase chain reaction amplification of the DNA samples. The three male patients with a female donor were studied by amplification of a Y chromosome specific sequence (DYZ1), allowing the detection of one male cell in 10(4) female cells. In all three cases, residual male nucleated cells were detected. The analysis was performed by amplification of the 33.6.3 minisatellite sequence for the 12 remaining patients. No residual recipient cells were detected within the sensitivity limit of the method which is 1% in that case. This suggests that detection of residual host cells depends on the sensitivity of the technique used.