LIMITING DILUTION ANALYSIS OF ALLOANTIGEN-REACTIVE LYMPHOCYTES-T .4. ONTOGENY OF CYTOLYTIC LYMPHOCYTE-T PRECURSORS IN THE THYMUS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 2  (4-5) , 245-255
Abstract
The ontogeny of development of cytolytic T lymphocyte (CTL-P) precursors in the murine thymus was investigated. Fetal or newborn thymocytes harvested from C57BL/6 mice were cultured with irradiated allogeneic (DBA/2) spleen cells in limiting dilution mixed leukocyte microcultures and assayed for cytotoxicity against 51Cr-labeled P-815 (DBA/2) tumor target cells. By applying Poisson statistics to the data, minimal thymic CTL-P frequency estimates were determined. CTL-P were barely detectable in fetal or newborn thymuses (3-19 CTL-P/106 cells), but their frequency increased dramatically (to 44-127/106 cells) within 24 h of birth. Control adult (day 70) thymuses contained 300-400 CTL-P/106 cells. Mixing experiments indicated that the low CTL-P frequencies in newborn thymuses was not due to a suppressive phenomenon. Strong indirect evidence for functional CTL-P maturation within the neonatal thymus is provided.