Essential Guides for Isolation/purification of Cells

In cell-separation technology the term ‘component’ of a mixture corresponds to a group of cells, which is usually called a cell population and shares a number of common features. How many common features a group of cells has to share in order to be called a cell population depends on the interest of the ‘separator’. For example, a T-cell population may be a group of mononuclearwhite blood cells bearing CD3 antigens, while a helper cell population usually comprises mononuclearwhite blood cells bearing CD3 and CD4 antigens. Cells metabolize as long as they live independently, whether they remain in an actual state of activation or differentiation or they proceed to another one. This means that a whole cell must not change its appearance or functions, but some cell components are chemically modiRed either anabolically or catabolically. So for discussing cell separation the term ‘chemical modiRcation’ should be converted to ‘biological modiRcation’ and in this chapter the expression ‘without biological modiRcation’ will be deRned as puriRcation of cells without changes or signals for changes of cellular states of activation and/or differentiation. No technology has been developed so far which allows picking of cell populations directly out of pieces of plant or animal tissues. So a ‘mixture’ which will be separated is normally a suspension of single cells prepared from parts of plants, from organs or body Suids of animals and humans or from twoor three-dimensional in vitro cell cultures. These cell sources already contain preselected groups of cells, the so-called organ or Suid (e.g. blood) speciRc cells. Still, a series of populations differing in important features are present in most plant or animal body compartments. In these instances, it may be of interest to separate cells for studying their biology or for using some of their capabilities in medicine or biotechnology. Thus the following reSections on essential guides for separation/puriRcation of cells are based on separations deRned as processes of any scale by which cell populations of single-cell suspensions are separated from each other without biological modiRcation. Methods for Cell Separation without Biological Modi\cation