POSITIVE SELECTION OF CD34(-BLOOD STEM-CELLS AFTER THAWING - TECHNICAL ASPECTS AND CLINICAL USE() CELLS FROM CRYOPRESERVED PERIPHERAL)

Autologous stem cell transplantation has become an important therapy i n lymphoma, multiple myeloma and solid tumors. The rationale for the s election of CD34(+) cells from peripheral blood or bone marrow progeni tor cell collections is based on the observation that contaminating tu mor cells can be depleted approximately 3 to 6 logs. This procedure ma y be limited because of lack of sufficient numbers of progenitor cells in the leukapheresis concentrates. The use of frozen/thawed periphera l blood mononuclear cell (PBMC) samples makes it possible to pool two or even more stem cell harvests collected at different time points to increase the total number of CD34(+) progenitor cells. We report in th is work the feasibility of frozen/thawed peripheral blood CD34(+) posi tive cell selection, using the large-scale (Ceprate SC) and the lab-sc ale avidin-biotin immunoadsorption system (Ceprate LC). This procedure consists of a washing step and a positive selection step. Our results show that frozen/thawed CD34(+) cells were obtained with a purity of 86.68 +/- 3.62%, a viability of 97.94 +/- 0.97% and a recovery of 91.8 5 +/- 10.84% (range 80 to 112%). The CFU-GM assays were performed in a methylcellulose based medium; 89.13 +/- 19.63 colonies were obtained for 10(3) cells plated, Two patients were grafted with peripheral bloo d CD34(+) cells selected after freezing. Our clinical data show that t hese cells are capable of rapidly reconstituting hematopoiesis after h igh-dose chemotherapy.