Figure 4.

l-citrulline enhances mycobacterium-specific T cell proliferation in l-arginine-sufficient culture. (A–C) Carboxyfluorescein succinimidyl ester (CFSE)-labeled lymphocytes from P25 mice were cocultured with HK-BCG-pulsed wild-type macrophages for 72 h with titrating concentrations of l-arginine (A, gray histograms) and l-citrulline (A, black histograms). CFSE dilution of CD3⁺CD4⁺ T cells was analyzed by flow cytometry. Data are displayed as representative histograms (A), mean percent of divided cells (B), and proliferation index (C) as defined in the methods. Data are combined from two experiments. Error bars, SEM. *p < 0.05, **p < 0.01, ***p < 0.001 compared with no l-citrulline added according to Student’s t-test.