Effects of CEN1 HC-Br (a), CEN1 HC (b), CEN1 HC (1–20) (c) and CEN1 HC (Ser) (d) on TNF-α secretion from THP-1 cells. The peptides were added to PMA treated THP-1 cells in triplicate 30 min after the addition of LPS (0.1 ng/mL). Peptide concentrations ranging from 0.04 to 50 mg/L of CEN1 HC and CEN1 HC-Br, 0.04 to 500 mg/L of CEN1 HC (Ser) and 1 to 500 mg/L of CEN1 HC (1–20) were tested. Cytokine levels were measured in the cell supernatants by ELISA after six hours of stimulation. Data are presented as mean ± SEM with stimulated cytokine levels without peptide added set to 0%. Data was fitted to curves using a 4-parameter fit in the Origin software. The IC50 values were automatically calculated by the software. Due to an unsatisfactory curve fitting, IC50 for CEN1 HC-Br was estimated to be approximately 4 mg/L.