Overexpression of EmGFP-FPN1 constructs in Nos2 wild-type and Nos2^−/− PE-MΦ. (A–D) PE-MΦ were transiently transfected with empty EmGFP plasmids (left) or constructs coding for human FPN1 and EmGFP (right) linked to its N or C terminus, respectively. Subsequently, cells were infected with S. typhimurium and treated with PBS (A and B) or L-NIL (C and D) for 16 h. The number of intracellular bacteria was determined by immunofluorescence and is depicted as a function of GFP expression. For evaluation, PE-MΦ were grouped into 4 categories containing 0, 1–2, 3–5, or >5 bacteria per macrophage. Data were compared by ANOVA, followed by Bonferroni’s correction (n = 4 independent experiments). *, P < 0.05; **, P < 0.01; ***, P < 0.001.