Host and donor erythrocyte repopulation patterns after allogeneic bone marrow transplantation analysed with antibody-coated fluorescent microspheres.

Analysis of erythrocyte populations, using red blood cell antigen differences between host and donor as marker, was performed with a sensitive fluorescent microsphere assay to monitor marrow engraftment and mixed red cell chimaerism after allogeneic bone marrow transplantation (BMT). An adapted transfusion policy, using marker negative erythrocyte transfusions, was required for this analysis. In all patients the marrow graft was depleted of lymphocytes by counterflow centrifugation. Thirty-seven patients were evaluable for donor repopulation at one or more points in the first 6 months after BMT. At 0.5 month donor erythrocytes were detectable in 19 out of 22 patients. At 6 months donor erythrocytes were detectable in 100% of the evaluable patients. In the first 3 months after BMT the average donor erythrocyte repopulation in recipients of major ABO mismatched transplantations was delayed. Thirty-eight patients were evaluable for chimaerism at 6 months or later after BMT. A high incidence of mixed red cell chimaerism was observed varying from 50% to 71% at different points of analysis. Mixed red cell chimaerism with low percentages (less than 1%) of host cells was not related with relapse, nor did high percentages (greater than 10% of host cells necessarily indicate relapse.