Possibility of progenitor cell mobilization during the hematological recovery following peripheral blood stem cell autograft.

Twenty-four patients with hematological malignancies were studied during recovery following autografting in order to establish the proportion of patients that show CD34+ cell mobilization and the kinetics of mobilized CD34-positive cells. The patients showed a peak in peripheral blood (PB) CD34+ cells after a median of 14 days (range 12-20) following reinfusion. According to the number of circulating CD34+ cells, two groups could be clearly distinguished: 17 patients (group A) with <10 PB CD34+ cells/microl (median 1.2, range 0-5) and 7 patients (group B) with >10 CD34+ cells/microl (median 51, range 13-123). Compared to group A, patients of group B showed a faster hematological reconstitution of both polymorphonuclear leukocytes >500/microl (12 vs. 15 days) and platelets >50,000/microl (12 vs. 17 days). The expression of the beta1 integrin CD49d was similar in the two groups of patients, while a lower expression of the beta2 integrin CD11a and a greater expression of the L-selectin CD62L were observed in the PB CD34+ cells of group B patients. Both in the PB and in the BM, the number of CFU-GEMM, CFU- GM, CFU-E and BFU-E of group B was significantly greater than that of group A. However, when the clonogenic potential of a single CD34+ cell was evaluated, no major differences in the number of colonies produced per CD34+ cell were found between the two groups.