Multipotent and Committed CD34(+) Cells in Bone Marrow Transplantation

In order to study the role of CD34(+) cells in hematological recovery following bone marrow transplantation (BMT), bone marrow cells stained with HPCA‐1 (CD34) and MY‐9 (CD33) monoclonal antibodies were analyzed by using a fluorescence‐activated cell sorter on or about days 14 and 28, as well as at later times, following BMT in 6 recipients. Single cell cultures of CD34(+) cells were also performed to evaluate their in vitro hematopoietic function. CD34(+) cells were detectable in bone marrow cells on day 14. More than 80% of CD34(+) cells co‐expressed the CD33 antigen, and macrophage (Mac) colony‐forming cells predominated among total colony‐forming cells of CD34(+) cells. In normal bone marrow cells, CD34(+), CD33(+) cells amounted to about 40% of CD34(+) cells, and the incidences of erythroid bursts, granulocyte/macrophage (GM) colonies, and Mac colonies were similar to each other. After more than 10 weeks, CD34(+), CD33(−) cells gradually recovered, as erythroid burst colony‐forming cells increased following GM colony‐forming cells. This phenomenon was well‐correlated with the time course of peripheral blood cell recovery. CD34(+), CD33(+) cells as committed progenitors and CD34(+), CD33(−) cells as multipotent stem cells have distinctive biological behaviors in BMT.