Flow Cytometry
Flow cytometry allows single cell measurements to be made using a variety of simultaneously measured parameters. Each cell in a heterogeneous mixture (such as blood cells) can be labeled using monoclonal antibodies carrying fluorescent chemical tags. Each of these cells can then be characterized as to cell size and surface characteristics. This is accomplished by measuring the fluorescence signals, and laser light scatter signals, from cells passing through one or more laser beams. This is the basis for lymphocyte phenotyping which can identify certain human leukemia, and is important in research dealing with bone marrow transplantation. Other applications for flow cytometry have been devised. Flow cytometry is useful in ploidy analysis of tumors cells, which can' serve as an indicator of the malignancy of certain cancers. Studies of the way the cell's internal signaling pathways transmit information has been possible through the use of certain fluorescent dyes which bind calcium. Anomalies in these pathways can lead cells to become cancerous. In addition to analytical characterization of cell phenotype, some flow cytometers - called cell sorters, can separate any identified cell type into a purified population of only those cells. Thus it is not only possible to characterize cells in complex mixtures, but also to separate them into pure populations. This is called cell sorting, and can be done under sterile conditions to yield viable cultures of highly purified cells. Availability of purified populations of cells has allowed rapid progress in the field of cellular immunology. Flow cytometry and cell sorting are relatively new technologies that are still evolving and being used in an ever-widening circle of new applications.
The flow cytometry unit of Medco Laboratories houses a cell sorter called the ELITE, which is Coulter's most advanced cell sorter. Its improvements over previous systems include an optical flow cell which permits capture of more signal from the sample/laser interaction point, thus allowing a fivefold increase in sensitivity compared to older flow chambers. The added sensitivity allows the use of small air-cooled laser. Potentially, as many as four lasers can be put to simultaneous use on this instrument. The instrument's overall design results in more rapid and convenient operation, compared to the former generation of sorters.
