Cord blood transplants: early recovery of neutrophils from co-transplantedsibling haploidentical progenitor cells and lack of engraftment of cultured cord blood cells, as ascertained by analysis of DNA polymorphisms

The number of infused cells is a very important factor in cord blood transp lant (CBT) engraftment. Prior ex vivo expansion of aliquots of transplanted cord blood (CB) units is being investigated as a procedure to increase eng raftment potential, but results are difficult to evaluate due to a lack of markers for assessing the contribution of expanded cells. We transplanted f ive patients, infusing the best available CB unit and cells from a second d onor simultaneously. In two patients, these cells were obtained from anothe r frozen CB unit by CD34(+) positive selection and culture expansion; the o ther three patients received uncultured highly purified haploidentical CD34 (+) cells. The first two patients had DNA from the culture expanded CB cell s detected only for a few days around day +11 when the absolute neutrophil count (ANC) was < 200/mul; thereafter and when the ANC was > 500/mul, only donor DNA from the uncultured CB was detected. For the other three patients , DNA analysis showed early and transient granulocyte engraftment of haploi dentical cells, progressively replaced by the CB-derived granulocytes. We c oncluded that: (1) simultaneous infusion of lymphocyte-depleted HLA highly mismatched haematopoietic progenitor cells has not produced unfavourable ef fects for CBT; (2) the double transplant model is suitable for evaluating t he engraftment potential of ex vivo cultured CB cells in the clinical setti ng; (3) the culture conditions used did not result in early recovery of ANC ; and (4) co-transplantation of purified uncultured HLA haploidentical CD34 (+) cells may reduce the time of neutropenia following CBT.