Direct ELISA analysis of LPS-treated IL-6 was performed by coating wells of a 96-well plate with 100µl per well of IL-6 diluted in carbonate/bicarbonate buffer at a concentration of 2 µg/ml overnight at 4C. Wells of the plate were washed, blocked with starting blocking buffer, and incubated with 100ul per well of a rabbit anti-IL-6 oligoclonal antibody at a serially dilution of 1:50, 1:100, 1:250, 1:500, 1:1000, 1:2000 and 1:5000 for 90 minutes at 37C. The plate was washed, then incubated with 100µl per well of an HRP-conjugated goat anti-rabbit IgG secondary antibody at a dilution of 1:5000 for 90 minutes at 37C. Detection was performed using 1-Step Ultra TMB substrate for 5-10 minutes at room temperature in the dark. The reaction was stopped with Stop solution, and absorbances were read on a spectrophotometer at 450-550nm.