Over the past 15 years many investigators have undertaken experiments to study ex vivo
expansion of hematopoietic cells. These studies have led to a number of clinical trials to
evaluate ex vivo–expanded cells in patients [1–11]. These trials have demonstrated that ex
vivo–expanded cells can be cultured and safely infused. Several studies have shown that ex
vivo–expanded peripheral blood progenitor cells (PBPC) can provide more rapid neutrophil
engraftment and possibly some effect on platelet engraftment. However, the cost and …