Intracellular Detection of T-Cell Cytokines: Differentiation of TH1 and TH2 Cells

The use of cytometry has become very important in different fields of modern biology and medicine (1 -4 ). In addition to the simple measurement of cell surface marker expression to define certain cellular subsets in basic research as well as in clinical settings, more complex assays have been developed in recent years to analyze, for example, physiological responses, apoptosis, or cell cycling (5 -9 ). The expression of intracellular proteins is another important feature for characterizing cellular function. The development of multicolor cytometers as well as the growing number of fluorochromes and dyes makes it possible to perform more complex analyses.