GENERAL CONCEPTS ABOUT CELL SORTING TECHNIQUES

Research involving cell analysis frequently requires isolation of cert ain cell types or subcellular components either as a final objective o r as a preparative tool for further assays. At present, there are a hi gh number of cell sorting methods that are suitable for being used in the clinical laboratory. These methods can be divided into two major g roups: (1) bulk sorters and (2) single-cell-based sorters. This latter group mainly refers to fluorescence-activated cell sorting (FAGS) by flow cytometry (FCM). In both cases, separation of cell subsets is bas ed on their classification according to one or more cell characteristi cs. In bulk sorters, cell classification and sorting are usually achie ved in a single step; by contrast, in FAGS techniques, these two steps are independent sequential processes. In addition, bulk sorters gener ally use a single-cell characteristic to isolate cell subsets and have a higher throughput rate, as compared with FAGS by FCM, where several parameters can be used simultaneously to classify cells for their fur ther isolation. As a consequence of the mechanisms underlying these tw o cell sorting methods, the balance between cell purity and cell recov ery on the sorted fraction are generally different, the single-cell-ba sed methods usually providing both a higher purity and recovery. Thus, in practice, bulk separation methods are frequently used either as a preparative step for FCM-based cell sorting or for the enrichment of t he sample in specific cell subsets, when a high throughput rate is req uired; in contrast, FAGS by FCM is selected for the isolation of cell subsets when a high purity and, especially, recovery of a specific sub population of cells present in a sample are needed.