Major histocompatibility complex restriction between hematopoietic stem cells and stromal cells in vivo

Graft failure is a mortal complication in allogeneic bone marrow transplantation (BMT); T cells and natural killer cells are responsible for graft rejection. However, we have recently demonstrated that the recruitment of donor-derived stromal cells prevents graft failure in allogeneic BMT. This finding prompted us to examine whether a major histocompatibility complex (MHC) restriction exists between hematopoietic stem cells (HSCs) and stromal cells. We transplanted bone marrow cells (BMCs) and bones obtained from various mouse strains and analyzed the cells that accumulated in the engrafted bones. Statistically significant cell accumulation was found in the engrafted bone, which had the same H-2 phenotype as that of the BMCs, whereas only few cells were detected in the engrafted bones of the third-party H-2 phenotypes during the 4 to 6 weeks after BMT. Moreover, the BMCs obtained from the MHC-compatible bone showed significant numbers of both colony-forming units in culture (CFU-C) and spleen colony-forming units (CFU-S). These findings strongly suggest that an MHC restriction exists between HSCs and stromal cells.