THE ONTOGENY OF TERMINAL DEOXYNUCLEOTIDYL TRANSFERASE POSITIVE CELLS IN THE HUMAN-FETUS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 61  (6) , 1125-1131
Abstract
The ontogeny of cells containing the enzyme terminal deoxynucleotidyl transferase (TdT) in human fetal liver, bone marrow and thymus was studied using a highly specific antiserum to TdT together with monoclonal antiprecursor cell antibodies in double and triple marker immunofluorescence. TdT+ cells were 1st observed in fetal liver at 12 wk of gestation and accounted for 55% of the lymphoid-like cells isolated after Ficoll-Hypaque separation. TdT+ cells were 1st observed in the bone marrow 16 wk after gestation. Like TdT+ cells in normal infant bone marrow, the majority of TdT+ cells in fetal liver and bone marrow expressed both BA-1 and RFB-1 antigens. Fetal TdT+ cells apparently include progenitors of the B lineage (BA-1+) and perhaps of thymocytes (RFB-1+). TdT was not observed in fetal thymocytes until after 20 wk of gestation, although thymic blasts and the majority of thymocytes were strongly RFB-+ from 12 wk of gestation. Fetal thymus apparently is 1st populated by TdT-, RFB-1+, BA-1- cells, but does not exclude the fact that a 2nd wave of TdT+ prothymocytes, possibly bone marrow derived, also exists.