Granulocytopoiesis. I. Senescence and Random Loss of Neutrophilic Granulocytes in Human Beings.

I N ORDER to understand and describe quantitatively a cell proliferation process like that of myelopoiesis, it is necessary to define the various subcompartments of proliferation, maturation and storage and the functional compartment as has been done by Killmann et al.’ However, of equal impor tance is the nature of the losses from the functional compartment, namely the circulating blood, and its quantitative description. The purpose of this paper is to analyze the disappearance of segmented neutrophils based on the assumption that there are two distinct means by which neutrophilic granulocytes disappear from the peripheral blood, namely random emigration and senescence, and to define the relationships between these two processes. The attainment of these objectives was made possible by the in vivo tritiated thymidine ( H3TDR) labeling of granulocytes.2’3 Simultaneous serial sampling of granulocytes from the blood and from extravascular sites gives information oP the loss of granulocytes by migration. Comparison of the sequence of labeling in segmented neutrophils and in their circulating pyknotic and karyorrhectic forms, described first by Undnitz,4 provides data to estimate some time parameters of the process of senescence of the granulocytes.