PRINCIPLES OF FLOW-CYTOMETRY

Clinical flow cytometry is a relatively new and rapidly growing medica l technology. According to estimates, there were less than 1000 instru ments in operation globally prior to 1985.(1) Most of these instrument s were used exclusively for research, and required dedicated facilitie s and operators with extensive backgrounds in electronics. In the mid- 1980s, with the availability of benchtop clinical models, the number o f flow cytometers jumped dramatically, surpassing 4000 by 1990.(1) Mos t of the instruments that have been sold in the past decade are equipp ed with low Power, air-cooled argon ion lasers with a fixed emission l ight wavelength at 488 nm. They are capable of multi-color immunopheno typing, and are usually connected to powerful personal computers for d ata analysis. By 1992, there were an estimated 7000 flow cytometers in operation worldwide.(1) Today, the three general fields where this te chnology is well established are clinical immunology, laboratory hemat ology, and medical oncology. The most prominent uses of flow cytometer s are for immunological characterization of lymphomas and leukemias, c rossmatching tissues for organ transplants, and counting lymphocyte su bpopulations in the peripheral blood of HIV-infected individuals. In t his review, a brief historical introduction will he followed by a gene ral description of some of the salient features of clinical flow cytom eters.