1. ¹Unidad de Hematopoyesis, CIEMAT, Hospital Puerta de Hierro, Universidad Autónoma de Madrid, Madrid, Spain
2. ²Servicio de Hematología y Hemoterapia, Hospital Puerta de Hierro, Universidad Autónoma de Madrid, Madrid, Spain
3. ³Hospital Clínico, Universidad de Valencia, Spain

Correspondence: Dr/Professor MN Fernández, Universidad Autónoma de Madrid, Head of the Servicio de Hematología y Hemoterapia, Hospital Universitario 'Clínica Puerta de Hierro', C/San Martín de Porres, 4, 28035 Madrid, Spain. E-mail: manueln.fernandez@uam.es

⁴Current address: Oncología, Hospital Niño Jesús, Madrid, Spain.

Received 24 May 2004; Accepted 6 October 2004; Published online 22 November 2004.

Abstract

We have reported short periods of post transplant neutropenia in human patients co-transplanted with cord blood (CB) and low numbers of haploidentical mobilized peripheral blood (MPB) CD34+ cells. To investigate the effect that the proportion of MPB to CB cells may have on engraftment kinetics, we have co-transplanted fixed numbers of human CB CD34+ cells mixed with different numbers of MPB CD34+ cells into NOD/SCID mice. We periodically quantified the proportion of human cells and the relative contribution of MPB and CB cells to the human engraftment on marrow aspirates. At the lowest MPB/CB ratios (5 : 1, 10 : 1), the contribution of CB cells predominated at all time points analyzed, and in three out of four experiments MPB cell contributions progressively decreased from day +15. At higher MPB/CB ratios, MPB cells had a more important contribution to both early and late engraftment, with the highest cell ratio resulting in only marginal CB cell engraftment. Therefore, our results showed greater potential, on a per cell basis, of human CB vs MPB cells for competitive sustained engraftment in the xenogeneic model used, which was only abrogated by the co-infusion of very high numbers of MPB cells.