The role of the laboratory in marrow manipulation

A variety of manipulations are performed on marrow for transplantation. Allogeneic transplantation may require red blood cell or plasma removal if the transplant is ABO incompatible, or T-cell depletion if there is a high risk of graft-vs-host disease. Autologous marrow must be preserved, either in the liquid or frozen state. If there is a chance of neoplastic cell involvement, these cells need to be killed or removed. Initial processing generally involves production of a buffy coat. Automated means using blood cell processors are available. Further purification of the desired progenitor cells may include discontinuous density gradient centrifugation. Depletion techniques can be physical (eg, elutriation or sheep red blood cell rosette removal) or chemical (eg, treatment with 4-hydroperoxycyclophosphamide). Monoclonal antibodies can be used covalently bound to toxin molecules, attached to magnetic beads, or with an exogenous source of complement. Antibodies to the CD34 human hematopoietic marker allow positive selection of desired progenitor cells. Quality control of marrow processing involves measurement of various hematologic parameters, careful process monitoring, bacterial/fungal and hematopoietic progenitor cultures, quantification of residual contaminating cells, and observation of clinical effect. Alternate sources of progenitors for transplant include peripheral blood, cord blood, fetal liver, and cadavers.