This study is designed for septic patients, to isolate MDSCs and the correlation of prognosis of sepsis. The purpose of this study hopes to explore the phenomenon and possible mechanisms of MDSCs in patients with severe sepsis.

Inclusion Criteria:

• Patients must have known origin of infection .
• Systemic inflammatory response syndrome.

Exclusion Criteria:

• age less than 18 years
• pregnancy
• known anaphylactoid reaction to colloid fluids
• a life expectancy less than 24 hours,
• inability to provide informed, written consent
• Patients receiving nephrotoxic drugs,
• admitted to the hospital following a surgical procedure,
• sepsis more than 72 hours when screening .

The investigators will include patients admitted with diagnosis of sepsis in this study.

Sepsis is defined by the consensus committee of American College of Chest Physicians and Society of Critical Care Medicine. The investigators will interview each patient and their family members, and review the medical records to obtain the baseline information including demographic data, clinical diagnosis, and evidence of dementia or psychiatric disorders. Acute physical and chronic health evaluation (APACHE II) score will be rated by chart review of data obtained within 24 hours of admission. The underlying medical history will also be collected.