IL6 and neoplasm: Importantly, in mice depleted of IMs, administration of IL-6 alone was sufficient to induce significant vascular leakiness, suggesting it acts downstream of IM activation and upstream of EC dysfunction, and that it is sufficient to compensate for the effects of IM activation by tumour EVPs (Extended Fig. 4f), further suggesting IL-6-mediated signaling between IMs and endothelial cells.