The concept of acquired immunodeficiency after a first severe infection in the ICU is widely described in the literature. There is a dual risk: increased mortality and increased secondary infections. Several approaches of immunostimulatory treatments have been proposed in the literature. The treatment proposed by this study consists of the administration of Granulocyte-macrophage colony-stimulating factor (GM-CSF), colony stimulating factor widely used particularly in the USA where it is marketed. A phase 2 clinical trial was conducted in Germany in 2009.

The main objective is to measure the incidence of ICU-acquired infections in 2 groups of patients treated by GM-CSF or placebo. ICU patients at risk are defined as surviving at D3 from a severe sepsis or septic shock and presenting a sepsis associated immunodepression. The detection of immunosuppressed patients will be achieved by measuring the HLA-DR (Human Leucocyte Antigen DR)with a threshold of less to 8000 sites.

Our hypothesis is that the number of secondary infections (primary endpoint) will be significantly reduced in the treated group.

Inclusion Criteria:

ICU patients presenting a severe sepsis or a septic shock associated with a sepsis-induced immunosuppression.

1. - Severe sepsis OR septic shock defined by the association of: at least 2 criteria of Systemic Inflammation Response Syndrome (SIRS) a clinically or microbiologically defined infection and respectively at least one organ failure (level ≥ 2 in one organ failure of the SOFA score) OR the need of a vasopressor treatment (epinephrine or norepinephrine ≥ 0,25mg/kg/min for at least 6 hrs to maintain a systolic pressure ≥ 90 mmHg or a mean arterial pressure ≥ 65 mmHg).
2. - AND Sepsis-induced immunosuppression: reduced mHLA-DR levels (< 8,000 monoclonal antibodies (mAb) per cell at D3).

Exclusion Criteria:

1. - Therapeutic limitation
2. Evolutive hemopathy, neutropenia < 500/mm3, stemcell transplant
3. Solid tumor with on-going chemotherapy or radiotherapy
4. Human immunodeficiency virus (HIV) infection with CD 4 count < 200 cell/mm3
5. Immunosuppressive treatment (including corticosteroid at immunosuppressive dose : > 10 mg equivalent prednisolone and cumulative dose > 700 mg)
6. Primary immunodeficiency .
7. Extra corporeal circulation within one month
8. Recent cardio-pulmonary resuscitation (within the current clinical episode)
9. Patients admitted in ICU for extensive burns
10. Contraindications to sargramostim
11. Pregnant or lactating women
12. Participation to another interventional study.