Fig. 3. A disruption in the integrity of the host IKK complex causes defective NF-B translocation in response to infection. Nuclear extracts were prepared from WT, IKK^–/–, IKKß^–/– and double-knockout IKK^–/–ß^–/– MEFs after different periods of infection with T. gondii. Cells were infected at an m.o.i. of 5:1. Translocation of p50 (A) and p65 (C) was examined by immunoblotting, and densitometric analysis of corresponding protein bands (B,D) was performed as described in the Materials and Methods. The kinetics of p50 (A,B) and p65 (C,D) translocation in WT cells paralleled the robust response seen with the phosphorylation of IB shown in Fig. 2. Contrary to this, only moderate increases in p50 and p65 translocation were observed in all IKK mutant cell lines at early stages of infection. IDV, integrated densitometric value.