Human postnatal CD4^- CD8^- CD3^- thymic T cell precursors differentiate in vitro into T cell receptor δ-bearing cells

The signals required for activation and the differentiation of human triple negative postnatal thymocytes were studied in vitro. Highly purified populations of CD4-, CD8-, CD3- (triple negative) thymocytes were isolated by combined panning and preparative cell sorting and the ability of triple negative thymocytes to proliferate in response to various cytokines determined. Maximal triple negative proliferation was obtained using a mitogenic combination of CD2 antibodies and either rIL-2 or the phorbol ester, PMA. Long term growth (2 to 6 wk) of postnatal triple negative thymocytes was best achieved using CD2 antibodies and rIL-2. After in vitro culture with CD2 antibodies and rIL-2, triple negative thymocytes gave rise to TCR-δ+ cells beginning on day 2 of culture (~15% CD3/TCR-δ+) reaching maximum (~60% CD3/TCR-δ+) on day 7 with stable number of TCR-δ+ cells observed in vitro for up to 6 wk. Analysis of 30 clones of human postnatal triple negative thymocytes demonstrated 9 of 30 (30%) were TCR-δ+, βF1-, essentially ruling out overgrowth of the triple negative population over time by a minor pool of contaminating TCR-δ+ cells. Thus, these studies have defined an in vitro culture system for human postnatal T cell precursors and demonstrated that precursors of human TCR-γδ+ T cells reside in the triple negative thymocyte pool.

Duke Scholars

Author Joanne Kurtzberg Pediatrics, Transplant and Cellular Therapy

Author Barton Ford Haynes Medicine, Duke Human Vaccine Institute