ARG1 and neoplasm: Therefore, we assessed the transcription levels of ARG1, iNOS, and NOX2. Although there were no significant changes in the mRNA levels of NOX2 and ARG1 in splenic MDSCs among groups, the expression levels of NOX2, ARG1, and iNOS were significantly increased in tumor-infiltrating MDSCs after Tg treatment, as compared with the vehicle control group (Figures 5D-I).