TLR expression by U937 cells in the absence or presence of the treatment with LPS, pam2CSK4 or both LPS and pam2CSK4. U937 cells were treated with or without 100 ng/ml of LPS, pam2CSK4 or both LPS and pam2CSK4 for 24 h. After the treatment, cellular mRNA levels of TLR1, TLR2, TLR4 and TLR6 were quantified using real-time PCR and normalized to GAPDH mRNA.