NEW YORK (Reuters Health) March 19, 2002 -- Transplantation of cord blood stem cells may provide "complete clinical immune recovery," according to a report in the February 15th edition of Blood.

The immaturity and naivety of cord blood T cells provide a broad polyclonal T-cell receptor repertoire, the authors explain, but they also raise concerns about the potential for long-term immune reconstitution. Dr. Antoine Toubert from Hopital Saint-Louis in Paris, France and colleagues compared T-cell receptor (TCR) diversity and T-cell receptor rearrangement excision circles (TRECs) after cord blood transplant in 29 patients and after HLA-identical sibling bone marrow transplant in 19 patients. All patients in both groups had successful engraftment of their transplants, the authors report, and the rates of acute and chronic graft-versus-host disease were comparable.

TCR diversity was low in both groups 1 year after transplantation, the report indicates, but by 2 years post-transplant nearly 90% of the cord blood transplant patients showed TCR polyclonality, compared to only 56% of the bone marrow transplant patients.

Similarly, the mean TREC values (a measure of the thymus's ability to produce new T cells) were significantly higher in the cord blood transplant group than in the bone marrow transplant group at the latest follow-up, the researchers note.

"These results indicate that despite the much lower number of CD34+ cells infused, recovery of normal T-lymphocyte diversity in cord blood transplant recipients was comparable, or even better, to that observed after HLA identical sibling bone marrow transplant matched for age and GVHD," the authors conclude.

"These data provide an experimental rationale to the favorable clinical outcome of cord blood transplant once engraftment and hematologic recovery have been achieved," the investigators say. Blood 2002;99:1458-1464.