High-dose cyclophosphamide for autoimmunity and alloimmunity.

High-dose cyclophosphamide (high-CY) is a potent immunosuppressive regimen that is increasingly used to mitigate both autoimmune and alloimmune conditions. Differential expression of aldehyde dehydrogenase between hematopoietic stem cells and lymphocytes accounts for the differential sensitivity of these cells to high-CY and explains why this regimen is immunosuppressive but not myeloablative. This article describes the clinical translation of high-CY for the treatment of autoimmune and alloimmune conditions.