B-Cell Depletion and Prevention of Hemolysis in Allogeneic Peripheral Blood Stem Cell Transplantation with Minor ABO Incompatibility.

Immune hemolysis is a severe complication of allogeneic peripheral blood stem cell (PBSC) transplantation with minor ABO-incompatibility, principally observed after conventional allogeneic PBSCT. The B-cell depletion of the PBSC graft is a prophylactic intervention which may decrease incidence and severity of this event. Eight patients who underwent allogeneic PBSCT in our institution between August 1999 and April 2004 were analysed. They all received a B-cell depleted transplantation performed because of minor ABO-incompatibility. There were 5 males and 3 females and the median age was 42.5 years (19–65). The pre-transplant diagnosis were solid tumours for 2 patients and haematological malignancies for 6. All received allogeneic PBSC recruited by G-CSF from 3 HLA identical unrelated and 5 HLA identical sibling donors. The median number of nucleated cells and CD34+ cells harvested were 7.75x10⁸ /Kg (3.9–11) and 6x10⁶/kg (4.3–8.7) and the median number of infused cells were 5.5x10⁸ /Kg (3.4–8.71) and 5x 10⁶/kg (3.1–8.33) respectively. Two patients received myeloablative and 6 patients reduced intensity conditioning regimens (RIC). As graft-versus-host-disease (GVHD) prophylaxis, cyclosporin with methotrexate was given after myeloablative conditioning. After RIC, cyclosporin alone (n=4) or cyclosporin associated to methotrexate (n=1) or cyclosporin associated to mycophenolate mofetil (n=1) were given. The ex-vivo manipulation consisted of a negative CD19 immuno-selection using the Isolex 300 I Baxter procedure. The median number of CD19+ cells (x10⁶/kg) before and after ex-vivo manipulation was respectively 73 and 0.05, which represented a B-cell log depletion of 3.16. The ex-vivo manipulation nevertheless induced a nucleated cell depletion of 20% (from 7.75 x10⁸ cells/kg to 5.52x10⁸ cells/kg after B-cell depletion) and a CD34+ cell loss of 18.5% (from 6x10⁶ cells/kg to 5x10⁶ cells/kg). Engrafment was observed for all patients and median time to neutrophiles (>0.5 G/l) and platelets (>50 G/l) recovery were respectively 19 and 12 days. Acute GVHD occurred for 5 patients whereas 3 patients developed chronic GVHD. At last follow-up, 4 patients died, 3 due to progressive disease, one due to hepatic GVHD. None of these 8 patients developed any clinical severe hemolysis, except one patient who presented a biological hemolysis with the development of a positive antiglobulin test 3 weeks after transplantation, without any consequences. Three months after transplant and at the last follow-up, the 4 long-term alive patients showed a stable erythropoietic reconstitution with an ABO-RhD donor determination. These data indicate that B-cell depletion is an efficient and safe method which could be used in case of minor ABO incompatibility.