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 γcommon (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 transfected 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 intermediateaffinity 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.