Pulmonary endothelial chimerism after hematopoietic stem cell transplantation.

PURPOSE: Few studies have investigated pulmonary endothelial chimerism after hematopoietic stem cell transplantation. In the present study, we investigated pulmonary endothelial chimerism using the ABH histo-blood group antigen as an identifying marker in cases of ABO-incompatible hematopoietic stem cell transplantation.

METHODS: Sixteen lung samples were analyzed. Of these, seven were explanted lungs from lung transplant recipients with severe pulmonary chronic graft-versus-host disease (GVHD). The remaining nine were autopsy samples from patients who died from various causes, and six of these nine cases had a diagnosis of pulmonary chronic GVHD. The ABH histo-blood group antigen was used to differentiate donor cells from recipient cells immunohistochemically. We estimated the percentage of vessels positive for donor blood group antigens in comparison with the total number of vessels.

RESULTS: Donor blood group antigens were expressed in the endothelium of 13 samples, all of which were pathologically diagnosed with pulmonary chronic GVHD. The proportion of vessels with donor group antigens ranged from 0.1 to 17.5%. In contrast, no chimeric vessels were observed in the three samples without pulmonary chronic GVHD.

CONCLUSIONS: Our results demonstrate that circulating stem cells engraft into the endothelium to a considerable extent in pulmonary chronic GVHD.