Basic Principles of Flow Cytometry

Abstract

The concept of flow cytometry has been in existence for more than five decades. With the emergence of antibodies and fluorochrome chemistry and the advances in laser and computer technology, flow cytometry has become a powerful and indispensable tool for the diagnosis of hematopoietic and lymphoid disorders. Although limited, it can be also used for determining cell types of solid tissue neoplasms. Current flow cytometers have the capability of simultaneously measuring multiple parameters of individual cells in a cell suspension. Thus, a large number of cell specimens can be processed with a quick turnaround time. In addition, flow cytometry is also highly sensitive and can detect immunophenotype of cells in a specimen with thousands of cells. The parameters analyzed by flow cytometry include physical properties of cells; the size, cytoplasmic granularity, and amount of DNA contents; and cell antigens/markers (surface, cytoplasmic, and nuclear) that can be recognized by specific antibodies. By using appropriate antibody panels, flow cytometry can reveal the cell type (hematopoietic, lymphoid, or nonhematopoietic), cell lineage (B- and T cells, natural killer cells, myeloid/monocytic cells, neuro/neuroendocrine cells, and epithelial cells), cell maturation stage (precursors vs. matured cells), and B-cell clonality of expressing immunoglobulin light chains. Moreover, flow cytometry allows us to sort cells based on their distinct parameters for clinical and research purposes. In this chapter, we outline the basic principles of flow cytometry for understanding when flow cytometry will be helpful and how to interpret flow cytometric data for disease diagnosis. Importantly, flow cytometry analysis results must be correlated with clinical presentations and pathological findings for accurate diagnosis.