Purpose: To study whether there is a relationship between transplanted cell dose and rate of hematopoietic recovery after peripheral-blood stem-cell (PBSC) transplantation, and to obtain an indication whether specific subsets of CD34 ' cell populations contribute to rapid recovery of neutrophils or platelets.Patients and Methods: Based on data from 59 patients, we calculated for each day after PBSC transplantation the dose of CD34 ! cells that resulted in rapid recovery of either neutrophils or platelets in the majority (> 70%) of patients. Using dual-color flow cytometry, subsets of peripheral-blood CD34 ' cells were quantified and the numbers of CD34 ' cells belonging to each of the reinfused subsets correlated with hematopoietic recovery following high-dose chemotherapy.Results

We performed a detailed kinetic study on the in vivo effect of a single subcutaneous dose of granulocyte colony-stimulating factor (G-CSF; 300 micrograms) in four healthy individuals on the expression and function of neutrophil Fc gamma receptors (Fc gamma R). G-CSF did not induce Fc gamma RI (CD64) on circulating neutrophils. However, neutrophils newly formed in response to G-CSF were Fc gamma RI positive and were able to perform antibody-dependent cellular cytotoxicity in an Fc gamma RI- dependent way. Fc gamma RII (CD32) expression was not changed significantly. Fc gamma RIII (CD16, phosphatidylinositol-linked) expression, slightly increased immediately (30 minutes) postinjection, was found to be strongly decreased on the newly formed population. For comparison, we studied the expression of the PI-linked proteins leukocyte alkaline phosphatase (LAP) and CD14. Intracellular levels of LAP mirrored the biphasic expression pattern as membrane-bound Fc gamma RIII. In contrast, CD14 expression on neutrophils was initially constant, followed by high levels on the newly formed neutrophils. Soluble CD14 levels were found to be elevated transiently, whereas peak levels of soluble Fc gamma III were observed as late as 6 days postinjection. In conclusion, we have shown that G-CSF results in an immunophenotypically and functionally altered neutrophil population for an important part as a result of its effect on myeloid precursor cells.

Adhesion molecules play a role in the migration of hematopoietic progenitor cells and regulation of hematopoiesis. To study whether the mobilization process is associated with changes in expression of adhesion molecules, the expression of CD31, CD44, L-selectin, sialyl Lewisx, beta 1 integrins very late antigen 4 (VLA-4) and VLA-5, and beta 2 integrins lymphocyte function-associated 1 and Mac-1 was measured on either bone marrow (BM) CD34+ cells or on peripheral blood CD34+ cells mobilized with a combination of granulocyte colony-stimulating factor (G-CSF) and chemotherapy. beta 1 integrin VLA-4 was expressed at a significantly lower concentration on peripheral blood progenitor cells than on BM CD34+ cells, procured either during steady-state hematopoiesis or at the time of leukocytapheresis. No differences in the level of expression were found for the other adhesion molecules. To obtain insight in which adhesion molecules may participate in the homing of peripheral blood stem cells (PBSCs), the number of CD34+ cells expressing these adhesion molecules present in leukocytapheresis material was quantified and correlated with hematopoietic recovery after intensive chemotherapy in 27 patients. The number of CD34+ cells in the subset defined by L-selectin expression correlated significantly better with time to platelet recovery after PBSC transplantation (r = -.86) than did the total number of CD34+ cells (r = -.55). Statistical analysis of the relationship between the number of CD34+L-selectin+ cells and platelet recovery resulted in a threshold value for rapid platelet recovery of 2.1 x 10(6) CD34+ L-selectin+ cells/kg. A rapid platelet recovery (< or = 14 days) was observed in 13 of 15 patients who received > or = 2.1 x 10(6) CD34+ L-selectin+ cells/kg (median, 11 days; range, 7 to 16 days), whereas 10 of 12 patients who received less double positive cells had a relative slow platelet recovery (median, 20 days; range, 13 to 37 days). The L-selectin+ subpopulation of CD34+ cells also correlated better with time to neutrophil recovery (r = -.70) than did the total number of reinfused CD34+ cells (r = -.51). However, this latter difference failed to reach statistical significance. This study suggests that L-selectin is involved in the homing of CD34+ cells after PBSC transplantation.

A sufficient number of PBPCs for two or three transplantations can be harvested from most patients without much difficulty before high-dose therapy. Two full-dose CTC courses or three tCTC courses can be given safely and with acceptable toxicity at 5-week intervals. Organ toxicity rather than bone marrow toxicity has become dose-limiting for alkylating agents.

We performed a detailed kinetic study on the in vivo effect of a single subcutaneous dose of granulocyte colony-stimulating factor (G-CSF; 300 micrograms) in four healthy individuals on the expression and function of neutrophil Fc gamma receptors (Fc gamma R). G-CSF did not induce Fc gamma RI (CD64) on circulating neutrophils. However, neutrophils newly formed in response to G-CSF were Fc gamma RI positive and were able to perform antibody-dependent cellular cytotoxicity in an Fc gamma RI- dependent way. Fc gamma RII (CD32) expression was not changed significantly. Fc gamma RIII (CD16, phosphatidylinositol-linked) expression, slightly increased immediately (30 minutes) postinjection, was found to be strongly decreased on the newly formed population. For comparison, we studied the expression of the PI-linked proteins leukocyte alkaline phosphatase (LAP) and CD14. Intracellular levels of LAP mirrored the biphasic expression pattern as membrane-bound Fc gamma RIII. In contrast, CD14 expression on neutrophils was initially constant, followed by high levels on the newly formed neutrophils. Soluble CD14 levels were found to be elevated transiently, whereas peak levels of soluble Fc gamma III were observed as late as 6 days postinjection. In conclusion, we have shown that G-CSF results in an immunophenotypically and functionally altered neutrophil population for an important part as a result of its effect on myeloid precursor cells.