Flow cytometric evaluation of leukocyte function

The marriage of monoclonal antibody technology and flow cytometry has provided clinical researchers with a powerful tool for the characterization of leukocytes from various sources. In this regard, flow cytometry has been primarily used for the immunophenotyping of peripheral blood lymphocytes in leukemias and various immunodeficiency disorders. Flow cytometry is also useful for the evaluation of leukocyte function in vitro and in vivo. This review discusses the various applications of flow cytometry for the assessment of leukocyte function. Since several cell surface antigens are important constituents involved in cell function, immunofluorescence identification of these markers can provide significant information regarding cell function. Analysis of activation antigen expression by monoclonal antibodies and flow cytometry can provide significant insights about the presence of functional leukocyte populations in patients. Flow cytometry can also be used to directly analyze leukocyte function. Procedures for the quantitative flow cytometric analysis of proliferation of activated lymphocyte subsets are reviewed. Early cell activation is also amenable to flow cytometric measurement. Early activation events such as alterations in membrane potential, intracellular free calcium redistribution, intracellular pH, and changes in membrane fluidity, as well as the direct measurement of enzyme activity, are also described.