Figure 1. L-Arg depletion induces downregulation of CD247 and additional membrane antigens, arrests cells in G₀/G₁ and inhibits cell proliferation in human Jurkat and peripheral blood mitogen-activated T cells. Jurkat (A) and peripheral blood mitogen-activated T cells (B) were incubated in the absence of L-Arg for the indicated times, and then cells were subjected to flow cytometry to determine the expression of the indicated membrane antigens, measured as mean fluorescence intensity (MFI), and compared with respect to control cells (C) grown for the same periods of time in the presence of L-Arg. (C) Cells incubated in the presence (Control) and in the absence of L-Arg for 24 and 72 h were analyzed for cell cycle profiling. Representative histograms, from at least five different experiments, show cell cycle arrest in G₀/G₁ following L-Arg deprivation, and the percentages of T cells at G₀/G₁ phase are shown in each cell cycle profile. (D) Cells incubated without L-Arg were counted at the indicated times as a measurement of cell proliferation. Data in (A, B and D) are means ± SD of three independent experiments.