Effect of LPS on ERK1 and ERK2 activation in human monocytes. Effect of LPS on ERK1 and ERK2 activation in human monocytes. Cells (2 × 106 cells/sample) were incubated with 10 ng of LPS/ml, 1 μM fMLP, or 80 ng of PMA/ml for the indicated times. Samples were analyzed by SDS-polyacrylamide gel electrophoresis and Western blotting with an ERK1-ERK2 phosphospecific antibody which recognizes only the activated forms of ERK1 and ERK2. ERK1 appears as the upper band (44 kDa); ERK2 appears as the lower band (42 kDa). The depicted data are typical of those from three independent experiments. Tjomme van der Bruggen et al. Infect. Immun. 1999; doi: