Decreased ROS production by MDSC and myeloid cell types after celecoxib-treatment. Production of reactive oxygen species (ROS) by (immature) myeloid subtypes from the spleen of tumour-bearing mice was measured. Splenocytes were obtained from tumour-bearing mice receiving either control diet or celecoxib diet for 10 days after tumour injection. Subtypes were identified based on characteristics as described in Figure 1. ROS production was reduced by MDSC in tumour-bearing mice treated with celecoxib diet. Mean fluorescent intensity (MFI) of ROS was significantly lower in MO-MDSC (p = 0.015) and Gr-1low Subset 2 MDSC (p = 0.017) after celecoxib-treatment. The MFI of ROS on macrophages did not significantly change (p = 0.14).