is there a role for alloreactive T lymphocytes?
The use of hematopoietic stem cells for in utero transplantation to create permanent hematochimerism represents a new concept in fetal therapy, although this approach has provided quite heterogeneous results. Flake and Zanjani have provided an excellent updated review of the current knowledge of in utero stem cell transplantation and have formulated diverse possible reasons for its poor clinical success.1 In fact, the only clear success, or claims of success, has been obtained in fetuses affected by immunodeficiency syndromes such as severe combined immunodeficiency (SCID) or bare lymphocyte syndrome. Flake and Zanjani strongly support the possibility that in such immunodeficiency disorders there is a selective advantage for donor cells, which then overcome a biological barrier to engraftment in fetuses. To date, the nature of this biological barrier remains unknown. Alternatively, or perhaps additionally, we have raised the possibility that the fetus may develop an allogeneic immune r
