Stimulation of IL-6 production by TLR4, TLR2 or TLR4 plus TLR2 activation. U937 cells were treated with 100 ng/ml of LPS, 100 ng/ml of pam2CSK4, 100 ng/ml of pam3CSK4, LPS plus pam2CSK4, LPS plus pam3CSK4, or pam2CSK4 plus pam3CSK4 for 24 h. After the treatment, IL-6 released into culture medium was quantified using ELISA. The data presented are the representative of 5 independent experiments with similar results.