Figure 8. Arginase 1 activity is required for VLC –mediated T cell suppression.

(A and B) Splenocytes were harvested and labeled as in Fig. 7. As indicated, cells were unstimulated or were stimulated with either PMA or plate bound αCD3; and this was done in presence of media alone, in the presence of 10⁵ CD11c⁺ cells from ID8 tumor ascites, or in the presence of 10⁵ CD11c⁺ cells from tumor ascites pre-incubated for 1h with 1mM nor-NOHA. Cells were incubated for 72h, and CD8⁺ and CD4⁺ T cell division was subsequently assessed by FACS. (C) Supernatants were harvested from the above assays and IFNγ concentration determined by ELISA. In all cases, data represent results from ≥3 independent experiments with the standard deviation shown. Statistical significance (*p<0.05, **p<0.01,***p<0.005, NS- No significance) was determined with the paired Student’s t test (Stimulated cells with CD11c⁺ VLCs or with nor-NOHA treated CD11c⁺ cells were each compared against stimulated controls with media alone).