Lymphocyte Production and Life-span in the Bone Marrow of the Guinea Pig

Guinea pigs were given 14 daily injections of ³H-thymidine to label a proportion of cells with a slow rate of turnover in addition to rapidly proliferating cells. In the bone marrow the only unlabeled cells were some reticular, endothelial, and plasma cells, damaged cells, and 14.1% of small lymphocytes. Six weeks after discontinuation of ³H-thymidine 7% of the marrow lymphocytes remained labeled. In guinea pigs injected every 4 hr with ³H-thymidine for 4 days to label all cells entering DNA synthesis, 14.4% of small lymphocytes remained unlabeled along with some reticular, endothelial, phagocytic, monocytoid, damaged, and plasma cells. The pattern of appearance of labeled lymphocytes was consistent with the kinetics of transitional cells that function as their precursors. Thus, in the bone marrow of the guinea pig the majority of lymphocytes have a short lifespan and a rapid turnover, whereas about 14% turn over more slowly and 7% have a life-span exceeding 4 wk. In this respect the kinetics of marrow lymphocyte production differs from that of the rat.