Western blot analysis of Y. pestis infected macrophages showed increased phosphorylation of inhibitor protein IκBα versus uninfected controls (Figure 4B), thus confirming our observation from the HCI studies, that during the early stages of infection, Y. pestis induces phosphorylation of IκBα, which leads to NF-κB activation and translocation. Here, NFKB1 is linked to infection.