Fauno L. Cordes

THE SEQUESTRATION AND VISCERAL CIRCULATION OF LEUKOCYTES IN MAN

The rapidly changing conditions of hematological equilibrium that have been encountered require a more dynamic approach to this problem than was anticipated during the initial phases of these investigations. The definition of “sequestration of leukocytes,’’ therefore, has been expanded to encompass the dynamic concept of hematologic equilibrium and to include the process of withdrawal of leukocytes from the peripheral circulation, selectively or collectively; the storage, transfer, and destruction of the intact leukocyte in this site; the ultimate fate and destiny of the remaining intact leukocytes; and the products of disruption of the destroyed leukocytes (FIGURE 1). The life span of the leukocytes may be arbitrarily divided into three phases (FIGURE 2). They are (1) the hematopoietic phase-that period from the initiation of the development of the leukocyte from its basic primitive cell to the point at which it is delivered into the peripheral circulation; (2) the intravascular phase-the duration that the leukocyte spends in the peripheral circulation; and (3) the extravascular phase-that period of time the leukocyte spends out of the peripheral circulation in viscera or in the tissues proper. Although these three phases appear distinct, the boundaries are probably not intact and invite a free flow of leukocytes back and forth with surprising ease and rapidity. Each type of leukocyte under discussion-be it the neutrophil, eosinophil, basophil, monocyte, or lymphocyte-probably has a different life span. Furthermore, it is likely that the life span of the immature forms of these specific types, if they make their way into the peripheral circulating blood, may also differ from those of the mature form of the same type. The life span of a leukocyte, therefore, does not exist per se, but would be a mean value of all the cells. The free access of leukocytes to the various hematological compartments, in all probability, influences the life span of any single cell type material, and renders a mean life span of all cells of lesser value than is generally considered. The extravascular store of leukocytes is extremely large in number. One can liken the peripheral circulating blood to the tip of a floating iceberg, in that one merely sees a small part of the entire hematological picture in the peripheral circulation, while the major functions are in the hemapoietic and extravascular regions which are beneath the surface. That this extreme variability and dynamic state is present in the normal individual, but is under control, and is unchecked in the abnormal leukemic state may account for the wide variations which are observed in the peripheral blood and tissues. I t has been suggested previously that the normal hematological state is a reflection of the equilibrium between production and removal, and that the leukemias may exhibit an unbalance between production and removal.’ With