Inclusion Criteria of Experimental group :  Male (XY) and female (XX) aged from 6 months to 7 years old.  Subject hospitalized either for:  (1) Urinary tract infection caused by Escherichia Coli, with:  Temperature ≥ to 38,5°C  Urinalysis  Leukocyte esterase + AND/OR Nitrites + AND/OR pyuria (≥ 100WBC/mm³) AND/OR bacteriuria.  Urinalysis  Clean catch voided urine: > 10^4 Escherichia Coli colony form unit (CFU)/mm (urine collection method for children >3 years old or toilet trained children or by stimulation for children <3 years old) Transurethral bladder catheterisation: > 10^4 Escherichia Coli colony form unit (CFU)/mm³ (urine collection method for children <3 years old).  Suprapubic aspiration: > 1 Escherichia Coli colony form unit (CFU)/mm³ (urine collection method for children <3 years old).  (2) Pneumonia with pleural effusion with :  Temperature ≥ 38,5°C Chest radiography/ultrasound: Pleural effusion  Streptococcus pneumoniae identified on blood or pleural fluid culture or by PCR  (3) Sepsis with:  Documented or suspected infection Temperature < 36° or > 38.3°C  Heart rhythm:  2 SD above normal for age 6-23 months: >180/min 24-71 months: >140/min 72-84 months: >130/min  Respiratory Rate:  6-23 months: >35/min 24 - 71 months: >30/min 72-84 months: >20/min  WBC:  6-23 months: >17500/µL or <5000/µL 24-71 months: >15500/µL or <6000/µL 72-84 months: >13500/µL or <4500/µL and/or CRP (blood) > 2SD above normal  And at least two of the following:  PaO2/FiO2 <300 Proven need for >50% FiO2 to maintain saturation ≥ 92% Need for mechanical ventilation Glasgow score < 11 Urine output < 0,5mL/kg/h for at least 2h  Creatinine:  6-11 months: >0,4mg/dL 12-23 months: >0,5mg/dL 24-59 months: >0,8mg/dL 60-84 months: >1mg/dL Or creatinine increase more than 0,5 mg/dL Platelet count <100000/mL Bilirubin >2 mg/dL  Mean arterial pressure (MAP)  6-11 months: <55 mmHg 12 -23 months: <60 mmHg 24-59 months: <62 mmHg 60-84 months: <65 mmHg SBP less than two SD below normal for age Prolonged capillary refill: > 5 sec  Inclusion Criteria of Control group :  Male (XY) and female (XX) aged from 6 months to 7 years old. Scheduled surgical intervention for a non-infectious pathology.  Exclusion Criteria:  Use of antithrombotic drugs (acetylsalicylic acid, thienopyridines, dipyridamol, glycoprotein IIb / IIIa antagonists, vitamin K antagonists, heparins). Congenital or acquired immunodeficiency: immunosuppressive drugs, hematopoietic stem cells transplantation, immunoglobulin therapy, extracorporeal membrane oxygenation (ECMO). Hemodialysis. 48h following cardiac operation of any type. Malignant cancer. HIV.