Immunomagnetic purging procedure for autologous bone marrow transplantation in lymphoid malignancies

In this report we describe the use of the immunomagnetic depletion of tumor cells from harvested bone marrow in two patients with acute lymphoblastic leukemia. The immunomagnetic procedure of purging involved one incubation of the marrow cells with a mixture of 4 monoclonal antibodies which bind to antigens of CD10 (ALB2), CD19 (HD37), CD20 (B1) and CD22 (HD39). Two incubations with magnetic beads (Dynabeads M-450) covered with antimouse antibodies followed by magnetic separation were performed. The bead/target B cell ratio was 50:1. After purging the recovery of mononuclear cells was 56% and 40%, while the recovery of CFU-GM was 45% and 38% respectively. Both patients engrafted rapidly without serious complications. One patient relapsed 4 months after transplant, the other remains in complete remission after 5 months. Our results confirm that the use of immunomagnetic beads is a simple, safe and reproducible technique to remove tumor cells before ABMT in patients with B malignancies using a broad mixture of MoAbs. However only a randomized trial using autologous marrow purged or not will clarify the effective clinical value of the procedure.