Sustained Immunosuppression

The goal of this clinical trial is to demonstrate the benefit of a standardized immunotherapy (Interferon gamma) on the incidence of secondary infections. . It will also learn about the safety of Interferon-gamma. The main questions it aims to answer are: Does Interferon-gamma: * reduces the Incidence of secondary infection episodes at three months * reduces the ICU mortality and at Day 90 * reduces the ICU and hospital length of stay * induces Biological immune restoration at Day 10 * has cost-consequence and cost-effectiveness Researchers will compare Interferon-gamma to a placebo (a look-alike substance that contains no drug) to see if Interferon-gamma works to treat sustained immunosuppression . Participants will: * Take Interferon-Gamma or a placebo for a maximum of 5 times between day 1 and day 9 * be monitored evety day until their ICU discharge and at day 30, 60 and 90