Cell collection.
Peripheral blood mononuclear cells (PBMCs) were isolated by Ficoll-Paque Plus (Amersham Biosciences) density-gradient centrifugation at baseline and at 1, 3, 6, 9, and 12 months after BM-MSC infusion. Cells were frozen in FBS with 10% DMSO and stored in liquid nitrogen until flow cytometry analysis was performed.