Monocyte and macrophage phagocytosis product assay

The detection method of monocyte and macrophage phagocytosis was according to previous publications [24]. After 72 h of culture, the density of monocytes and macrophages was approximately 2 × 10⁴ cells/well. In the treatment wells (three wells), dyed HCT-8 cells (1 × 10⁶ cells) were added to the monocytes and macrophages in each well followed by incubation for 10 h. In the control wells (three wells), MTT (Amresco) solution (5 mg/mL) was added to the monocytes and macrophages followed by incubation for 4 h. Then, the cells were washed three times with PBS (Hyclone), and 150 μL of dimethyl sulfoxide (Sigma) was added. The experiments were performed in triplicate. The absorbance of each well was detected at 575 nm and 630 nm (blank wells) with a Microplate Reader (BioTek, Winooski, VT, USA). Phagocytosis product (PP) was used as an indicator of the phagocytic ability of monocytes and macrophages and was calculated as follows: PP = absorbance (treatment wells) / absorbance (control wells).