Viability assay of RAW264.7 macrophages stimulated by rGSTO2 protein in vitro. Macrophages treated with LPS or PBS were used as positive or negative controls, respectively and the cells were treated with rGSTO2 protein at different concentrations (5–80 μg/mL) for 24 h, and then the cell viability was measured by a CCK-8 assay. Ns means that the difference is not significant, ** p < 0.01 and ***p < 0.001 versus the negative control. All data are expressed as means ± SD (n = 3).