| Research Abstract |
Objective The purified CD34+ cell fraction has been used for hematopoietic stem cell transplantation and gene ther apy since they were demonstrated to have long-termreconstituting ability. The presence of CD34- stem cells has been, however, recently recognized as a new class of stem cells independent of CD34+ cells in the human hematopoietic system. Therefore, the potential effects of CD34- stem cells on the clinical course have been a major concernin recipients of CD34+ selected transplatation. To address this concern, we used an invitro assay in transplant recipients to determine whether they have CD34- precursor population. Materials and Methods Lin-CD34-cells were isolated and analysed from bone marrow cells in eleven transplant recipients including four CD34- selected transplantations, six standard bone marrow transplantations, and one T cell-depleted marrow transplantation. Results The frequency of the Lin-CD34-population in four CD34-enriched transplatation recipients was not different from those of normal donors or of other modes of transplantation : 0.96ア1.01% (meanアSD, n= 4), 0.45ア0.16% (n=6), and 0.66ア0.59% (n=7), respectively. However, the Lin-CD34-population obtained from the recipients of CD34-enriched transplantation acquired neither CD34 expression nor colony for ming activity after 7 days of culture, wher eas the cells from all the normal individuals and standard BMT recipients were able to differentiate into CD34+ cells accompanied by the emer gence of colony for ming activity. Conclusion Recipients of CD34-enriched transplantation appear to have defects in their CD34= precursor population. The clinical significance of these defects will be determined in a life long follow-up of these patients.
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