Evaluation of Monocyte Expression of HLA-DR (mHLA-DR) in Geriatric Service

Inclusion Criteria: For all patients: * Patients aged over 75 hospitalised in one of the geriatric units defined as the research sites; * Patient affiliated to a social security scheme; * Patients or relatives who have been informed and have no objections to the research. To be eligible in the acute situation sub-population: \- Patients presenting with an acute episode on admission or following a stay in the research sites; The acute episode is defined, for example, by an infection, cardiac decompensation, a complicated fall, acute renal failure, any acute or decompensated cardiovascular pathology, any discovery of cancer that has not been stabilised. To be eligible in the stable situation sub-population: \- A patient who has not had an acute episode for at least 7 days. Exclusion Criteria: For all patients: * Patients under legal protection: curatorship, guardianship, safeguard of justice ; * Patients under exclusive comfort care for whom it has been decided not to take a blood sample; * Patients undergoing long-term antibiotic treatment, i.e. with no defined stopping date; * An immunocompromised patient or a patient undergoing immunosuppressive treatment (for example: HIV infection, a patient awaiting solid organ transplantation, a patient undergoing haematopoietic stem cell transplantation, a patient undergoing chemotherapy for a solid tumour or haematological malignancy, a patient suffering from an auto-immune disease and being treated with immunotherapy and/or immunosuppressive therapy and/or biotherapy, an asplenic or hyposplenic patient, a patient undergoing experimental potentially immunosuppressive treatment, a patient undergoing Eculizumab treatment, a patient presenting a hereditary immune deficiency). For patients in an acute clinical situation: \- Patient previously included in the same sub-population.