Figure 1
Conceptual scheme for non-myeloablative stem cell allografting. In step 1 stable mixed hematopoietic chimerism is established with immunosuppressive and minimally toxic conditioning therapy, thus minimizing regimen toxicities and GVHD with the initial transplant. This allows for step 2, the infusion of donor lymphocytes without rejection, resulting in eradication of host hematopoiesis including the graft-versus-leukemia reaction. Newer strategies for minimizing GVHD with step 2 include the use of T cell dose escalation schemes, of CD8-depleted DLI, and the insertion of a suicide (eg herpes simplex thymidine kinase) gene into the T cells that can be activated by drugs.
