CD68 and colitis: Similar to CD68+ specific macrophage infiltration, the expression of macrophage derived iNOS was upregulated in the colonic macrophages (Figure 4) as well as local gut epithelia, supporting the notion that ADI-PEG provides protection against colitis by preventing CD68+  macrophage proliferation and iNOS activation in colonic tissues from IL-10 deficient and to a lesser extent in WT animals (data not shown).