Role of Innate Lymphoid Cells in the Immunosuppression of Septic Shock

Septic shock is a major public health problem. Even if mortality is decreasing, it's still high. Sepsis is a heterogeneous syndrome that encompasses a gamut of immune responses occurring during the host's response to a serious, life-threatening infection. The immune phenotype in sepsis ranges from proinflammatory (systemic inflammatory response syndrome and cytokine storm syndrome) to anti-inflammatory (immune depressed state). In order to apprehend septic shock as a whole, investigators should made a whole immune mapping in each patient. Within immune mapping of septic shock patients, innate lymphoid cells (ILCs) have never been explored.

ILCs include natural killer (NK) cells and three other main subsets, ILC1, ILC2 and ILC3, referred as to 'helper-like ILCs'. Since their discovery, ILCs have been shown to contribute to wound healing and defense against infection, and studies have revealed critical aspects of their differentiation. They are studied by flow cytometry and much of the role of ILCs remains to be elucidated, especially in humans. Like T Helper cells, investigators think it could exist an imbalance of ILCs in the late course of septic shock which could participate to the immune depressed state and the increase of patients' mortality at this stage.

So, investigators want to realize a whole immune mapping in patients managed for a septic shock focusing particularly on the innate lymphoid cells. investigators think that ILC1s and ILC3s could be increased in the patients' blood in the early course of the disease and could participate to the cytokine storm syndrome. On the contrary, ILC2s could be increased in the late stage of the septic shock, in correlation with the immune suppressed state. investigators will compare the blood rates of ILCs in septic shock with the blood rates of ILCs in patients with a bacterial sepsis but without severity criteria.

investigators will include 30 patients in septic shock (group 1) in the medical intensive care unit of the Timone Hospital (RUM - Pr Gainnier) and 30 patients with a bacterial sepsis alone, during a 6 months period. investigatorswill take two kits of blood samples for the group 1, one during the early stage of the septic shock (48 first hours of care) and one during the late stage of the disease (between the fourth and the sixth day). investigators'll take only one kit of blood samples for the group 2. One kit includes one EDTA tube (5 mL) and five Lithium Heparin tubes (25 mL). The immune mapping will be made by Julien Carvelli, a gold medalist resident, in the framework of a Master 2. The analyses will be made in the laboratory of immunology in the Conception Hospital (Pr Vivier's team).