Stem cell transplantation eliminates alloantibody in a highly sensitized patient

Highly sensitized patients are forced to stay on transplant waiting lists f or many years and ultimately may never find a donor. Peripheral blood stem cell (PBSC) transplantation may provide a strategy to decrease host allorea ctivity through the production of a chimeric state. We investigated allorea ctivity and chimerism. in a highly sensitized 40-year-old patient with sick le cell disease who underwent a nonradiation based conditioning regimen con sisting of fludarabine, ATG, and high dose melphalan, for allogeneic stem c ell transplant. Host monocytes and lymphocytes became donor in origin by da y 14. PRA, initially 100% pretransplant, fell to 0 by day 263. Anti-red blo od cells antibody became undetectable by day 152. The use of a new nonradia tion-based conditioning regimen enabled successful engraftment of allogenei c donor PBSCs and the elimination of alloantibody. As new less toxic condit ioning regimens are developed, PBSC transplantation might provide a new sol ution to allosensitization.