9 - Granulocyte Kinetics in Health and Disease

Abstract

SUMMARY The kinetics of neutrophils in the blood, and of their precursors in the marrow, have been reviewed. The proliferation and maturation of marrow neutrophil precursors have been defined by studies using tritiated thymidine, and neutrophil production and release can be quantitatively assessed. Marrow culture techniques provide useful additional information concerning stem cells committed to granulopoiesis and monocytopoiesis. Techniques for the study of blood neutrophil kinetics have been reviewed, and although the results obtained differ they are probably valid if compared with normal results derived by the same technique. It is well established that blood neutrophils are partitioned between marginated and circulating pools, and that shifts between the two are important in various types of neutrophilia and neutropenia. The blood neutrophil pool is small in size compared with the number of mature neutrophils and neutrophil precursors in the marrow, the cells circulating for a relatively brief period before migrating actively (and randomly) out of the circulation. A continuous flow of viable neutrophils into the tissues is essential, and the most important determinant in assessing risk of infection is probably the neutrophil production (or turnover) rate rather than the circulating neutrophil number. Neutrophil kinetic studies have defined the mechanisms for many situations associated with neutrophilia, and in most patients it is possible to predict what the kinetic changes will be. In neutropenia, underproduction, excessive margination or shortened survival of neutrophils could all be contributing factors, and in the individual patient kinetic studies might be necessary to define the relative contribution of each. In infected patients, recent work suggests that abscess localization might be possible using newer isotopes, particularly 111In.