Concentration-dependent activation of IKK and IKKβ by LPS and TNF-. Human monocytic THP-1 cells were stimulated with increasing concentrations of LPS for 30 minutes or TNF- for 5 minutes and cytoplasmic lysates were prepared with anti-IKK antibody. The IKK kinase assay was done as described in Materials and Methods; the substrate was a fusion protein made of wild-type IκB (amino acids 1-54) and GST.