Counterflow centrifugal elutriation: present and future

Counterflow centrifugal elutriation (CCE) has been proposed as a method for separating heterogeneous cell populations into distinct subpopulations on the basis of different sedimentation characteristics, without impairment of cell function or yield. The advantages of this technique are the high recovery and viability of fractionated cells and the rapidity and reproducibility of results. CCE alone or in combination with other separation methods can provide homogeneous populations of cells for further investigations. Recently, CCE has been employed in clinical studies aimed at preventing GVHD in BMT recipients by depleting lymphocytes prior to BM infusion. Furthermore, ongoing studies are concentrating on the use of negative selection procedures on the fractions currently excluded from the graft with the purpose of adding these depleted fractions to the graft preparation to augment the number of stem cells, accessory cells and unselected lymphocyte subsets. In the experimental field, CCE combined with negative and positive selection techniques may be useful in the study of hematopoiesis by separating 'pure' stem cell populations from more committed hematopoietic progenitors. We review here the present and possible future applications of elutriation in the clinical and experimental field.