Distinction between γ(c) detection and function in YT lymphoid cells and in the granulocyte-macrophage colony-stimulating factor-responsive human myeloid cell line, Tf-1

Peripheral blood monocytes respond to interleukin-2 (IL-2) and express the γ common (γ(c)) subunit of the IL-2 receptor (IL-2R) complex. However, the role of IL-2 in myeloid development has recently become of interest for several reasons, including the effect γ(c) mutations may or may not have on myeloid development in patients with XSCID. Many studies of IL-2 function in the myeloid cell lineage have been performed on a murine background. To study γ(c) expression and function in human myeloid precursors, we introduced the human myelomonocytic cell line, Tf-1, with a retroviral vector containing the human IL-2Rβ subunit to create functional human intermediate IL-2R consisting of βγ(c) dimers. We have characterized this transfectad variant of Tf-1 (Tf-1β) with regard to its response to IL-2. Unlike the parental Tf- 1 cell line that is deficient in both IL-2Rα and IL-2Rβ expression, the Tf- 1β transfectant binds and responds to IL-2 through intermediate-affinity IL- 2Rs. Scatchard analyses indicate the number of intermediate-affinity receptors on Tf-1β is similar to the number found on the well-characterized YT cell line. However, detection of γ(c) on Tf-1β cells is dramatically less than on YT cells by Western blot analysis and is undetectable by flow cytometric studies and surface iodinations. The γ(c) component on YT cells is readily detected by all three methods. We conclude from these studies that the intermediate-affinity IL-2Rs on the Tf-1 cell line behave differently than those on YT cells with respect to γ(c) detection. Either the γ(c) molecule itself is different, or the cellular environment in which it functions is altered. Elucidation of γ(c) function on this cell line will allow for its use as a model in which other cytokines using γ(c) (including IL-2, IL-4, and IL-15) can be studied on the same cellular background.