Hereditary Haemorrhagic Telangiectasia (HHT, also known as Osler-Weber-Rendu Syndrome) is an disease that leads to the development of dilated and fragile blood vessels. We propose to take blood samples from patients with HHT, and culture white blood cells that express the proteins mutated in HHT, namely endoglin and ALK-1. We will study the properties of these cells which will involve their growth in media prompting different types of differentiation, or infection of cell lines with Epstein Barr virus to provide cell lines which can be repeatedly studied. It is anticipated that DNA, mRNA and proteins will be extracted from these cells for study of white cell responses and association with expression levels of endoglin and ALK-1 We hypothesize that these cells which express "half-normal" endoglin or ALK-1 will show altered protein synthetic differences when compared to normal white blood cells. We anticipate that that these findings may help to explain aspects of the HHT disease phenotype.