51Cr and DF32P labeling of human blood cells in leukocyte-rich plasma

Cell-rich plasma from human peripheral blood was labeled with disodium chromate (51Cr) and diisopropylfluorophosphate (DF32P), and the uptake and distribution of the radionuclides by granulocytes, lymphocytes, monocytes, and erythrocytes were studied. Velocity sedimentation through a 1-2% albumin gradient and electrophoresis in a Ficoll-sucrose gradient demonstrated that granulocytes migrated the fastest, followed by monocytes, and then by the mixture of lymphocyte-red cell populations. Monocytes accumulated four to five times as much 51Cr as the other leukocytes or the red blood cells. Erythrocytes showed a greater uptake of 51Cr than did granulocytes or lymphocytes. Granulocytes were preferentially labeled in vitro by DF32P, and the uptake of DF32P by lymphocytes was about one-third that by granulocytes. No measurable DF32P labeling of monocytes and only slight labeling of erythrocytes was observed by liquid scintillation counting of the labeled cells. These data have implications in the interpretation of in vivo survival studies of radiolabeled leukocytes.