A new 'two step' procedure for 4.5 log depletion of T and B cells in allogeneic transplantation and of neoplastic cells in autologous transplantation

To evaluate a new 'two step' method for purging T, B and neoplastic cells from hematopoietic progenitor cells (PC), PCs were collected by apheresis and some suspensions were deliberately contaminated with 2-5% breast cancer cells. PCs were first processed through CellPro columns for positive selection of cells that express CD34. After this first step, the mean CD34+ cell recovery was 68 +/- 12%, and CD34+ cell purity was 61 +/- 11%; CD3+ and neoplastic cell depletion were 2.1 +/- 0.4 and 1.9 +/0 0.4 logs, respectively. Cells were further processed through the StemSep device for direct depletion of T and B cells or of breast cancer cells. After the first and the second step, overall CD34+ cell recovery was 50 +/- 7%, T and B cell removal was 4.7 +/- 0.4 log and neoplastic cell purging was 4.4 +/- 0.3 log, ie significantly superior to methods described in the past.