Removal of metastatic neuroblastoma cells using magnetic immunobeads with newly produced antibodies were investigated. Magnetic immunobeads were M-450 (DYNAL) coated with purified sheep polyclonal IgG against all mouse IgG subclass. Two newly produced antibodies (5E9 and 3C1) and other two antibodies were used. Four antibodies were added to a mixture of the neuroblastoma cells stained with Hoechst 33342 with the human bone marrow cells. The magnetic immunobeads were added to the cell mixture. After incubation for 30 min at 4 °C , the magnetic beads reacted to the neuroblastoma cells were removed by using cobalt samarium magnets. The residual neuroblastoma cells were assayed under the fluorescence microscopy, and the clonogenic capacity of the bone marrow progenitor cells were measured by culturing in the soft agar assay. A ratio of neuroblastoma cells to normal bone marrow cells was 1:10 and a ratio of magnetic immunobeads to neuroblastoma cells was 100:1. A tumor cells depletion rate of 1.9-3.8 logs was achieved using the cocktail antibodies with 5E9, 3C1, NCC-LU-243 and NCC-LU-246 and second cycle treatment. In a clinical cell separation unit 2.81 log removal rate of tumor cells was obtained. Residual rate of human normal bone marrow cells after second cycle purging was 17.1%. Reduction in the clonogenic bone marrow progenitor cells was about 10%. This purging method in use the procedure with the magnetic immunobeads and neuroblastoma cell antibodies seems to offer advantage with respect to speed and simplicity. By use of suitable antibodies, the immunomagnetic tumor cell depletion method is useful in autologous bone marrow transplantion of advanced neuroblastoma children with poor prognosis. Newly produced antibodies 5E9 and 3C1 are of great use in the immunomagnetic tumor cell depletion procedure
