3 Neutrophil function tests

The complexity of the neutrophil response to inflammation creates many difficulties for the study of neutrophil function in vitro. The environment in which a neutrophil is placed can have marked effects upon a variety of cellular functions. Quantitative tests of neutrophil function present problems not only with assay design but also in the isolation of cells from peripheral blood without disturbing their normal physiology. It is desirable to isolate neutrophils from other leukocytes because soluble factors released by other cells can influence neutrophil function, and other cells may interfere with functional assays; for example, monocytes will phagocytose opsonized particles and eosinophils contain a potent peroxidase. Attention to physical parameters such as temperature, pH or osmolarity, and rigorous exclusion of endotoxin, permits neutrophils to be isolated in a resting state. Subsequent function tests must be selected with an understanding of normal neutrophil physiology and applied with an awareness of any associated technical problems. The investigation of abnormal neutrophil responses may necessitate the screening of several tests of function; for example, defective neutrophil killing may be the result of abnormal chemotaxis, phagocytosis or degranulation. Which tests are appropriate will depend upon the questions to be answered and on the quantity of cells available for study.