Fig 2.
Enzymatic arginine depletion by ADI modulates cytokine secretion of LPS-activated human moDC. Immature moDC (5 × 105 per sample) were exposed to the indicated amounts of recombinant ADI or, as a control, corresponding levels of ADIC424A (only the largest amount is shown), and 1 μg/ml LPS was added. Citrulline content was determined as a measure of the cumulative ADI activity and arginine depletion over the 24-h assay time (A). DC cytokine secretion into supernatants was assessed by ELISA and is expressed as a percentage of the amount secreted by LPS-stimulated cells not exposed to any ADI protein (B). Bars in panel A represent the mean ± SD from experiments with DC prepared from seven different donors. Symbols in panel B represent values from individual donors, and means are indicated by horizontal lines. Differences between the amounts of cytokines secreted by cells exposed to mutant (control) or active ADI were analyzed by paired (two-tailed) t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001.