IL6 and Increased total leukocyte count: To test whether the increase in endothelial IL-6 production during atherosclerosis contributes to the leukocytosis that fuels arterial inflammation19–22,25, we induced atherosclerosis in Cdh5CreERT2;Il6fl/fl mice using an atherogenic diet and adeno-associated virus (AAV)-mediated gene transfer of mutant human PCSK9. Compared to Cdh5CreERT2 littermate controls, endothelial cell-specific Il6 deletion reduced HSPC numbers and proliferation in the bone marrow and lowered systemic myeloid cell numbers (Fig. 8a–c), while splenic hematopoiesis remained unchanged (Extended Data Fig. 7d,e).