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

Inclusion Criteria: Patients * Patients who have provided written consent * Patients with national health insurance cover * Age \> 50 years * Patients with a diagnosis of Horton's disease, before any treatment Horton's disease is defined by the American College Rheumatology ACR criteria \[2\], as the association of 3 of the following 5 criteria: * age at disease onset 50 years or older * recent onset localized headache * indurated temporal artery or diminished/abolition of temporal pulse * erythrocyte sedimentation rate (ESR) greater than 50 mm during the first hour (or C Reactive protein (CRP)\>20 mg/L) * Positive temporal artery biopsy (TAB) showing vascularitis with infiltration by mononuclear cells or granulomatous inflammation with or without giant cells. Control subjects Control subjects will be healthy volunteers recruited among blood donors at Dijon University Hospital, voluntary hospital personnel (nurses, doctors, laboratory technicians and secretaries) and patients without infectious, inflammatory or auto-immune diseases or cancer (CRP\<5mg/L) recruited in the investigating departments of Dijon Hospital. They will be matched for age and sex and must meet the following criteria: * Age \> 50 years * Patients with national health insurance cover * Signed written informed consent form * Absence of an inflammatory syndrome (CRP\<5 mg /L) Exclusion Criteria: * Adult under guardianship * Persons without national health insurance cover * Pregnant or breast-feeding women * Patients treated with corticoids or immunosuppressants in the month preceding inclusion * Patients treated with chemotherapy