Migration of leukocytes to sites of injury or inflammation is a critical component of both innate and adaptive immunity. To penetrate venular walls, leukocytes must migrate through multiple barriers, endothelial cells (EC), the pericyte sheath and the venular basement membrane (BM) 1, 2. Although there is increasing interest and understanding of the mechanisms that mediate transendothelial cell migration (TEM), the relative contribution of individual molecules requires further clarification 1, 2. Within our group we aim to investigate the mode and mechanisms of leukocyte transmigration through imaging of inflamed tissues by multiple methods, including the application of high resolution confocal intravital microscopy. With this approach we have noted previously unreported physiological responses (eg ICAM-1-mediated sub-endothelial cell crawling 3) and also potential pathological events such as “disrupted” modes of neutrophil TEM 4. The latter includes the first direct observation of in vivo neutrophil reverse TEM (rTEM) within a mammalian system, a response that we have associated with reduced expression of JAM-C from EC junctions, indicating a key role for JAM-C in regulation of polarised luminal to abluminal neutrophil TEM 4. In investigating the pathophysiological relevance of rTEM we noted that this response was most prevalent following ischemia-reperfusion (I-R) injury and was associated with the presence of a subset of functionally primed neutrophils within the pulmonary vasculature which correlated with the development of acute lung inflammation 4. As loss of EC JAM-C from a primary site of injury/inflammation appears to be instrumental in turning a local inflammatory response to a systemic multi-organ phenomena, on-going works have aimed to elucidate the prevalence of this event and its associated mechanisms. Overall, through rigorous analysis of leukocyte-vessel wall interactions by direct real-time imaging of inflamed tissues, our findings provide novel insights into the cellular and molecular mechanism via which leukocytes breach venular walls in vivo, findings that are likely to identify novel and disease-specific phenomena. Collectively, our findings have contributed to the developing concept that neutrophils have a broader role in inflammation, immunity and pathogenesis of inflammatory disorders than conventionally considered, emphasising the need for greater insight into the mode, mechanisms and implications of neutrophil trafficking in vivo.