Processing and Storage of PBSC

Most PBSC products collected to support transplant procedures are autologous and must be cryopre-served for later use. In the allogeneic setting, products can be collected prior to starting pretransplant conditioning in the recipient or they can be collected on the day of intended infusion. In addition to cryop-reservation, other processing options exist, depending on the purpose for which the PBSC will be used. Specific engineering of the graft is possible to remove or expand desired cell populations

After collection, the PBSC product is taken to the stem cell processing lab. This is where procedures to ensure quality of the product take place, including determination of CD34+ cell content (see, viability determinations, mononuclear cell counts, and confirmation of sterility. Stem cell practice has attracted more regulatory attention recently. The Foundation for the Accreditation of Cell Therapy has been established to provide uniform standards for collection and processing of stem cell products, as well as the clinical care of both donors and recipients (Rowley 2002). The various procedures involved in stem cell processing have also attracted more scrutiny from the Food and Drug Administration. Options for stem cell processing include (a) depletion of granulocytes by density gradient centrifugation (Rowley et al. 1990), (b) depletion of potential tumor cells by a direct purging technique or CD34 selection (Civin et al. 1990), and (c) depletion of T cells in an allogeneic product to decrease the risk of graft-vs-host disease. Many of the stem cell processing steps described here and below, with the notable exception of CD34 selection, were developed using marrow products and all are made somewhat more complicated by the considerably higher number of cells found in PBSC compared with bone marrow.

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