Transferrin receptor induction in mitogen-stimulated human T lymphocytes is required for DNA synthesis and cell division and is regulated by interleukin 2.

Transferrin is required by many cells for growth. Mitogen-induced T lymphocyte proliferation is dependent on the presence of both interleukin 2 (IL-2; T-cell growth factor) and transferrin, even though resting lymphocytes do not have receptors for either. Exposure to mitogen (phytohemagglutinin) alone is sufficient to induce transient appearance of IL-2 receptors on lymphocytes. Using monoclonal antibodies to the IL-2 receptor and to the transferrin receptor, we examined those signals required for transferrin receptor induction during T lymphocyte proliferation. Our study has revealed that (i) monocytes, or a monocyte substitute such as the phorbol ester tetradecanoylphorbol 13-acetate, are required for transferrin receptor expression after mitogen exposure; (ii) the presence of IL-2 receptors is necessary for transferrin receptor induction; (iii) antibody to the IL-2 receptor inhibits thymidine incorporation (DNA synthesis) in lymphocytes, but only if administered before transferrin receptors have appeared; and (iv) antitransferrin receptor antibody inhibits DNA synthesis but has minimal effect on IL-2 receptor expression. Thus, IL-2 receptor induction leads to transferrin receptor induction and subsequent initiation of DNA synthesis. These data indicate that IL-2 stimulates T lymphocyte proliferation, at least in part, by induction of transferrin receptors on these cells.