Figure 4: Induction of cytokines and chemokines. Macrophage RAW 264.7 cells were treated with SWCNTs at 0, 2 and 20 μg/ml for 16 h. LPS at 1 μg/ml for 5 h was used as a positive control. The cell-free culture medium was collected and cytokines and chemokines were detected by flow cytometry using mouse cytometric bead array and Flex beads. Data represent mean ± SD. * p< 0.05, ** p<0.01.