VWF and anaphylaxis: The rationale for examining whether Angpt-2 is released during systemic anaphylaxis was based on the following lines of evidence: Angpt-2 is stored in the Weibel-Palade body along with von Willebrand factor and P-selectin in the endothelial cells, and is released via degranulation of that body in response to a large number of secretagogues [29], which include well-known anaphylactic mediators such as histamine [30], peptido-leukotrienes [10] and serotonin [11].