Study of Phenotypic and Functional Characteristics of Regulatory T Lymphocytes in Horton's Disease

Giant cell arteritis (GCA) is the most frequent vascularitis after 50 years of age The investigators recently showed that GCA was accompanied by an elevation in Th1 and Th17 response \[1\]. Even though a quantitative deficit in regulatory TL (Treg) was shown, there are to date no data concerning their precise phenotypic and functional characteristics and notably their ability to inhibit Th1 and Th17 polarisation. The hypothesis of the investigator is that, in GCA, there is quantitative and above all functional deficit of Treg. Recently, progress has been made in the identification of Treg with new markers (CD39), which will make it possible to better identify and to study their specific functions. In this study the phenotypic and functional characteristics of Treg in GCA will be analysed. Better understanding of the role des Treg in GCA should lead to better-targeted treatments for patients with GCA, notably via the blockage of cytokines that inhibit the differentiation and/or function of Treg. The study is classified interventional because a lot of blood samples are taken.