Maintenance of vascular integrity depends on cell-cell adhesion (Dejana et al., 2009) , and cell-cell communication mediated by Notch signaling plays a role in promoting the formation of primary (or patent) vessels over more permeable microvessels (Hellstrom et al., 2007; Leslie et al., 2007; Lobov et al., 2007; Roca and Adams, 2007; Siekmann and Lawson, 2007; Suchting et al., 2007) . By inhibiting these two interrelated processes, and possibly interactions between endothelial cells and other vascular cell types such as mural cells, anthrax toxins might contribute to the latestage effects of anthrax infection when disruption of endothelial barrier function leads to lethal vascular collapse. Once sufficient levels of anthrax toxins are produced, they can be fatal even if the bacterial infection is eliminated with antibiotic treatment. Thus, these studies of anthrax toxins initiated in flies and validated in mammalian models might ultimately have therapeutic implication for treating humans infected with anthrax or for other conditions compromising vascular integrity.