Treatment of autoimmune diseases by hematopoietic stem cell transplantation.

Remarkable advances have been made in bone marrow transplantation (BMT), which now has become a powerful strategy for the treatment of leukemia, aplastic anemia, congenital immunodeficiency disorders, and autoimmune diseases. Using various animal models, allogeneic BMT has been found to be useful in the treatment of autoimmune diseases. In MRL/lpr mice, which are radiosensitive (<8.5 Gy) and are an animal model for autoimmune disorders, conventional BMT resulted in only transient effects; the manifestations of the autoimmune diseases recurred 3 months after BMT. However, the combination of BMT plus bone grafts (to recruit donor stromal cells) was capable of preventing the recurrence of autoimmune diseases in MRL/lpr mice. This strategy was found to be ineffective in the treatment of MRL/lpr mice that had developed autoimmune diseases, because these mice were more sensitive to the effects of radiation after the onset of lupus nephritis due to uremic enterocolitis. We have recently discovered a safer strategy for treatment of autoimmune diseases, which includes fractionated irradiation (5.5 Gy x 2) (day -1) followed by portal venous injection (day 0) plus intravenous injection (day 5) of donor unfractionated bone marrow cells. We successfully treated autoimmune diseases in MRL/lpr mice using this strategy; 100% of MRL/lpr mice treated in this fashion survive >1 year after treatment. We identified the mechanisms underlying the components of this approach and have found that stromal cells play a crucial role in successful BMT. In this review, the conditions essential for successful allogeneic BMT are discussed.