CLONALITY STUDIES IN PATIENTS UNDERGOING ALLOGENEIC AND AUTOLOGOUS BONE-MARROW TRANSPLANTATION FOR HEMATOLOGICAL MALIGNANCIES

Twenty three allogeneic hone marrow transplant (BMT) patients with fem ale donors and 23 female autologous transplant patients were assessed for clonality status after transplant to determine the nature of haemo poietic reconstitution. The X chromosome probes PGK, HPRT and M27 beta were used to assess clonality by analysis of X chromosome inactivatio n. Results were obtained for 15 allogeneic patients, 14 of whom gave p olyclonal results after transplantation. One patient gave a skewed pat tern of X chromosome inactivation after transplant due to extreme Lyon isation of the donor cells. Results were obtained from 19 autologous t ransplant patients, 17 of whom gave polyclonal results after transplan t. Two patients gave patterns of skewed X chromosome inactivation in p ost-transplant samples, reflected in their constitutive DNA, due to ex treme Lyonisation. The remaining patients could not be assessed becaus e of hypermethylation of HpaII sites or indistinguishable digested and undigested alleles using M27 beta probe analysis. Haemopoietic recons titution after allogeneic and autologous BMT, in our patients, was fou nd to be polyclonal. Skewed patterns of X chromosome inactivation seen after transplant were due to extreme Lyonisation of the infused haemo poietic cells.