“…In recent years, several different migratory routes for immune cells over different cellular barriers into the CNS parenchyma have been characterized (Engelhardt and Sorokin, 2009; Wilson et al, 2010; Larochelle et al, 2011; Engelhardt and Ransohoff, 2012; Alvarez et al, 2013). However, the precise molecular mechanism responsible for homeostatic CNS immune surveillance and how inflammatory processes differ from regulatory/homeostatic processes on the immune cell side remain unclear (Flügel et al, 2011). Pressure to advance knowledge on the mechanisms of trans-endothelial diapedesis arose with the approval of therapeutic monoclonal antibodies interfering with cell trafficking.…”