RESUMO
BACKGROUND: CD34+ cells are capable of engraftment and hematopoietic reconstitution. However, expression patterns of other surface antigens such as CD13, CD33, CD38 and HLA-DR on CD34+ cells in mobilized peripheral blood have remained unclear. This study analyzed the expansion kinetics of the CD34+ cells and subsets in the peripheral blood of healthy donors treated with recombinant human Granulocyte Colony-Stimulating Factor (rhG-CSF), the relative composition of CD34+ subsets in mobilized peripheral blood and apheresis product, the yield of apheresis product. METHODS: The 6 peripheral blood stem cell donors received a daily dose of 500 microgram (8.1~10 microgram/kg) of rhG-CSF subcutaneously for 6 or 7 days. The hematologic parameters and the number of CD34+ cells and subsets in peripheral blood were recorded at baseline and daily for a total 6 to 7 days. With monoclonal antibodies which were designed for two color direct immnunofluorescence (IF) analysis with combination of fluorescence isothiocyanate (FITC) and phycoerythrin (PE) conjugated, CD34CD38, CD34HLA-DR, CD34CD13, and CD34CD33 surface antigens were analyzed by flow cytometry. RESULTS: The number of CD34+ cells mobilized to peripheral blood peaked at day 4 or 5 with rhG-CSF treatment. Circulating CD34+ cell expanded by 11.5-fold from 4.5 +/- 1.8x106/L before rhG-CSF treatment to maximal increment 51.9 +/- 13.4x106/L after mobilization. Subsets of CD34+CD38-, CD34+HLA-DR-, CD34+ CD13-, and CD34+CD33- (in % ofthe CD34+ cell) were all decreased and subsets of CD34+CD38+, CD34+HLA-DR+, CD34+CD13+, and CD34+CD33+ were all increased after mobilization, so that the numbers of early committed and myeloid committed progenitors were higher than the those of multipotent stem cells in mobilized peripheral blood and leukapheresed products. Each apheresis product yielded a mean of 451.6x106 (7.7x106/kg of RBW) CD34+ cell and 172.3x105 (2.9x105/kg of RBW) CFU-GM. CONCLUSION: Sufficient amount of CD34+ cells capable of engraftment and hematopoietic reconstitution can be mobilized by administration of rhG-CSF to healthy adult donor. Subsets of mobilized CD34+ cells were mainly composed of early committed and myeloid committed progenitors, although absolute numbers of all progenitor cells including multipotent stem cells were significantly increased.