REAnimation Low Immune Status Markers

The immunosuppression status will be determined from two immunological reference tests: (1) lymphocyte proliferation in response to ex vivo T cell stimulation (adaptive immunity) (Poujol et al., 2014) and (2) the production of tumor necrosis factor (TNF) by monocytes in response to ex vivo stimulation by lipopolysaccharide (LPS) (innate immunity) (Duffy et al., 2014). The values measured will be defined as normal or abnormal, depending on whether they are within reference intervals (RI) derived from an independent set of healthy volunteers. For this purpose, the definition of immunosuppression will be: an abnormal result in at least one of the two "reference" tests (outside the reference intervals defining normal values), and on at least two consecutive samples. The same reference test must be abnormal in two successive samples examined for the patient to be considered immunosuppressed.

Intensity of the innate immune deficiency will be measured using the production of TNF by monocytes in response to ex vivo stimulation by LPS (Duffy et al., 2014). Intensity of the adaptive immune deficiency will be measured using the lymphocyte proliferation in response to ex vivo T cell stimulation (Poujol et al., 2014). The values measured will be defined as normal or abnormal, depending on whether they are within reference intervals derived from an independent set of healthy volunteers. We will describe for all groups of patients:

• The proportion of patients with a deficiency of the innate immunity, defined by an abnormal TNF secretion test result after LPS stimulation, for at least two consecutive samples.
• The proportion of patients with a deficiency of the adaptive immunity, defined by an abnormal lymphocyte proliferation, for at least two consecutive samples.
• The proportion of patients with at least one abnormal test on Days 1, 3-4, 5-7, 13/18, 26/36 and 52/68

Reference tests being non-standardized and cumbersome to implement, and time to results being incompatible with clinical practice, the use of simpler and quicker tests, based on the use of new biomarkers, would allow the individualization of patient management based on the patient's immune status. One of the secondary objectives is to evaluate the performance of new biomarkers compared to the two reference tests to diagnose immunosuppression. Different types of markers and tests will be evaluated: Viral reactivation markers, host-response markers, immune functional assays, immunophenotyping.

To evaluate the association between the immunosuppression status as defined in primary objective and the occurrence of secondary infections related to healthcare, the association of the immunosuppression status upon the occurrence of secondary infection will be examined first, and secondly any possible association between the levels of each of the reference tests and the occurrence of secondary infections will be characterized. In this analysis, a secondary infection related to healthcare will be defined as an infection occurring after inclusion in the study, between inclusion and day 28.

We will examine the association between immunosuppression (as defined in the primary objective) and in-hospital mortality. Association will be evaluated par measuring occurrence of mortality at days 14, 28, 60 and 90, in the different groups.

The possibility of taking a sample before surgical stress should allow measurements of the impact of the procedure on the host response, and especially on any subsequent onset of immunosuppression. Oncological pathologies and treatments implemented prior to surgery may also be associated with immunosuppression, and for this reason patients hospitalized for cancer surgery will be compared to those hospitalized for vascular surgery. Impact of surgery on immunosuppression will be measured by comparing immune status as defined by the reference tests, in the population of surgical patients before and after surgery.