RAW 264.7 cells were seeded on 96-well plates at an initial density of 2×10 3 cells/well and incubated for 72 h at 37°C, 5% CO 2 until the cells were 80% confluent. The culture medium was replaced by 200 μl basic DMEM media without FBS and incubated for 30 min. Then the culture medium was replaced by 100 μl basic DMEM media containing 50, 100 and 200 nM of mAb, mAb-sCT and sCT, respectively (in quadruplicate). The cells were incubated for 4 h at 37°C. The medium was then replaced with 100 μl basic medium containing (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) (MTT) at a concentration of 100 μg/well and incubated for a further 4 h at 37°C. After removing the supernatant and washing twice with phosphate-buffered saline, the newly formed purple formazan crystals were dissolved in 200 μl solubilization solution using an in vitro toxicology assay kit (TOX-1, Sigma Aldrich, St. Louis, USA), and the absorbance was measured at 570 nm using a microplate reader.