Abstract
Phagocytosis is a cornerstone in protection against infections. Earlier methods for the quantification of phagocytosis had too low accuracy and precision to use it in clinical work. The advent of flow cytometry (FCM) made measurements of numerous phagocyte functions available to clinical practice, and experimental and clinical research. Miniaturisation of previous methods made phagocyte functions accessible in neutropenic patients.
FCM allows simultaneous and rapid quantification of the percentage of phagocytes, the number of phagocytosed targets (phagocytic index), attachment, internalization, phagosomal pH, respiratory burst, and the digestion and killing of bacteria and fungi. Each method can be related to antibody- and complement concentrations and their receptors. The accuracy and reproducibility of the methods are excellent. Derived parameters for overall phagocyte function, like the phagocytosis product (percentage phagocytosis multiplied by the phagocytic index) may supply useful information.
Various phagocyte functions are interrelated. FCM enables the simultaneous quantification of phagocytosis, oxidative burst and subcellular organelles on different leukocyte types in mixed cell suspensions. For example, polymorphonuclear neutrophilic granulocytes (PMNs) and monocytes can be discriminated by fluorescent antibodies. A multiparameter approach allows extensive investigations of phagocyte functions in a wide range of medical disorders.