BACKGROUND: G-CSF-mobilized PBPCs are utilized in allogeneic and autologous PBPC transplants. Homing, adhesion, and transmigration of hematopoietic CD34+ cells are required for successful engraftment. Hematopoietic CD34+ cells undergo directional migration toward the CXCR4 receptor ligand stromal-derived factor-1 (SDF-1). Limited data are available on the effects of liquid storage and cryopreservation on PBPC CD34+ cells. STUDY DESIGN AND METHODS: Magnetic-assisted cell sorting (MACS)-selected CD34+ cells were assayed for retention of in vitro transmigration and phenotypic changes of unit-matched liquid-stored and cryopreserved PBPC samples from healthy donors. Studies evaluated whether transmigration of CD34+ cells in Iscove's modified Dulbecco's medium plus 1 percent HSA alone or in medium supplemented with SCF or allogeneic plasma was affected by overnight incubation at 37 degrees C, relative to nonincubated conditions. RESULTS: Transmigration was maintained during liquid storage at 1 to 6 degrees C during a 2-day period and in unit-matched cryopreserved-thawed samples that had been initially liquid stored. Overnight incubation at 37 degrees C of MACS-selected unit-matched liquid-stored or cryopreserved-thawed CD34+ cells resulted in substantially increased transmigration, in particular with noncoated filters chemoattracted with the chemokine SDF-1. CONCLUSION: CD34+ cell transmigration was comparable between liquid-stored and cryopreserved samples, and both demonstrated similar increases after overnight incubation at 37 degrees C.