Figure 3.

l-citrulline metabolism prevents arginase-mediated suppression of anti-mycobacterial T cells. Carboxyfluorescein succinimidyl ester (CFSE)-labeled lymphocytes from P25 mice were cocultured with HK-BCG-pulsed wild-type macrophages (MΦ^WT) (A–C), HK-BCG-pulsed wild-type macrophages treated with BEC (D–F), or HK-BCG-pulsed Arg1^flox/flox;Tie2-cre macrophages (MΦ^ΔArg1) (G–I). Cocultures were incubated for 72 h with 1 mM l-arginine (black), 1 mM l-citrulline (gray), or neither amino acid (white). CFSE dilution of CD3⁺CD4⁺ T cells was analyzed by flow cytometry. Data are displayed as representative histograms (A,D,G), mean percent of divided cells (B,E,H), and proliferation index (C,F,I) as defined in Section “Materials and Methods.” Data are combined from three experiments. Error bars, SEM. **p < 0.01, ***p < 0.001 according to Student’s t-test.