Will mixed chimerism cure autoimmune diseases after a nonmyeloablative stem cell transplant?

Mixed chimerism after allogeneic bone marrow transplantation has been shown to cure a number of genetic disorders in both the clinical and experimental settings. Although encouraging results have been reported from animal experiments, the role of mixed chimerism in eliminating autoimmune disorders is not clear.

A 50-year-old man with extensive psoriasis received an allogeneic transplant from his brother after nonmyeloablative conditioning with fludarabine, melphalan, and Campath-1H for relapsed non-Hodgkin's lymphoma. The chimerism status and the immunological recovery after the transplant were serially monitored.

Twenty-one months after the transplant, the patient continues to be in complete remission from psoriasis and lymphoma with stable mixed chimerism (30% to 40% donor cells), despite significant recovery of T-cell subsets and antigen-specific response.

If mixed chimerism can be achieved safely with novel low-intensity conditioning regimens and results in sustained remission of autoimmune diseases, allogeneic transplantation may become a realistic therapy in the management of some patients with autoimmune disease.