ONTOGENY OF TERMINAL DEOXYNUCLEOTIDYL TRANSFERASE-POSITIVE CELLS IN LYMPHOHEMOPOIETIC TISSUES OF RAT AND MOUSE

  • 1 January 1979
    • journal article
    • research article
    • Vol. 123  (3) , 1347-1352
Abstract
Ontogeny of hemopoietic cells containing the enzyme terminal deoxynucleotidyl transferase (TdT) was studied in rats and mice. During fetal life TdT-positive cells were 1st detected in the thymus, where they appeared on or about day 17 of gestation. TdT-positive cells were not found in fetal liver, spleen or bone marrow but appeared in bone marrow and spleen on the day after birth. In the rat, peak levels of TdT-positive cells were attained at 3-4 wk of age in thymus, bone marrow and spleen, accounting for 67, 3.9 and 2.3% of nucleated cells, respectively. The percentages of TdT-positive cells in thymus and bone marrow decreased gradually thereafter, whereas TdT-positive cells in spleen were no longer detectable by 7 wk of age. Normal percentages of TdT-positive cells were found in bone marrow and spleen from neonatally thymectomized rats and congenitally athymic (nu/nu) mice. Dexamethasone treatment resulted in marked decrease in TdT-positive cells. The putative role of TdT-positive hemopoietic cells as thymocyte progenitors is discussed.