Blood chimerism in dizygotic monochorionic twins during five years observation

Dizygotic monochorionic twin pregnancies can result in blood chimerism due to in utero twin-to-twin exchange of stem cells. In this case, we examined the proportion of allogeneic red blood cells (RBCs) by flow cytometry and the proportion of allogeneic nucleated cells by digital PCR at seven months and again at five years. We found an increase in the proportion of allogeneic cells from 63% to 89% in one twin, and a similar increase in autologous cells in the other twin from 57% to 84%. A paradigm for stem cell therapy could be modelled on this case: induction of tolerance and chimerism by antenatal transfusion of donor stem cells. The procedure would hold the promise of transplantation and tolerance induction without myelo-ablative conditioning for inheritable benign hematological diseases like sickle cell disease and thalassemia. This article is protected by copyright. All rights reserved.