Origin and Kinetics of Resident Tissue Macrophages

Abstract

To elucidate the origin and renewal kinetics of peritoneal macrophages, as a typical example of the mononuclear phagocytic system, syngeneic rats were treated with tritiated thymidine ([3H]TdR) and leukocytes were transferred to unlabeled recipients over a bilateral arteriovenous shunt. Labeled and unlabeled monocytes were evenly distributed in both animals as shown by autoradiography. No autoradiographically detectable reutilization of label occurred and transferred cells showed undisturbed kinetics. The results imply the following: resident peritoneal macrophages derive from blood monocytes; peritoneal macrophages represent a homogeneous population in respect to their cellular origin; blood monocytes as a myelogeneous cell line do not represent a generative end cell; they migrate into the tissue (peritoneal cavity) and differentiate into resident macrophages, undergoing on average 1 mitosis/cell during a period of approximately 7 days; resident peritoneal macrophages are derived 50% from blood monocytes and 50% from division in situ; and under steady-state conditions the renewal rate amounts to 0.18%/h, which yields a half-life time of 16 days and a renewal time of 23 days.