ROBO4 and Sepsis: Interestingly, a recent study by London et al. (13) also found that activating an endothelium-specific, Robo4-dependent signaling pathway with the soluble ligand Slit could strengthen the vascular barrier, reduce vascular permeability in the lung and other organs, and increase survival in different murine models of sepsis, but did not alter plasma concentrations of a panel of cytokines and chemokines.