Marrow graft rejection by repeated transfusions of allogeneic donor spleen cells

Many hematological diseases require long-term transfusion support, which causes production of donor-reactive antibodies in sensitized recipients. Sensitized patients are at an increased risk for graft rejection when they undergo allogeneic hematopoietic stem cell transplantation (allo-HSCT). Here, we established a highly sensitized murine model to investigate the mechanism of donor graft rejection. After BALB/c mice were repeatedly transfused with allogeneic spleen cells from C57BL/6 mice, there was a significant increase in complement-dependent cytotoxicity in the serum of sensitized mice. For transplantation, 1 x 10(7) bone marrow cells (BMCs) from C57BL/6 mice were injected into lethally irradiated recipient BALB/c mice. Sensitized mice died between 12 and 15 days post-transplantation, while non-sensitized mice remained alive after 28 days. The hematopoietic recovery rate declined over time in sensitized recipients. The homing trace assay showed a rapid disappearance of donor BMCs in the spleen and bone marrow of sensitized recipients. In addition, the recipient cells and antibodies in the sensitized serum were capable of inducing high level of cell- and complement-mediated cytotoxicity to the donor graft. Our finding may explain the impaired hematopoietic stem cell homing and poor hematopoietic engraftment observed in highly sensitized allo-HSCT patients.