The purpose of this study is to evaluate the efficacy of thymosin alpha 1 for treating severe sepsis.

Severe sepsis is a disease of infectious origin with a high risk of death. Over the past decade, thymosin alpha1 have already provided clinicians with additional weapon in the fight against infectious diseases, but it is unknown whether thymosin alpha1 is effective in treating severe sepsis.

Inclusion Criteria:

• Severe sepsis according to ACCP/CCM criteria
• Patient or legally authorized representative able to provide informed consent

Exclusion Criteria:

• Subject is less than 18 years or more than 85 years of age
• If female, the subject is pregnant or nursing
• Subject is receiving immunosuppressive therapy such as cyclosporine, azothioprine,or cancer-related chemotherapy
• Patient not expected to survive 28 days because of uncorrectable medical condition, such as poorly controlled neoplasm or other end-stage disease
• History of bone marrow, lung, liver, pancreas, or small-bowel transplantation
• Acute pancreatitis with no established source of infection