To evaluate the dynamic alterations of Th2/Th1 for the prediction of clinical immunity and how it was related to 28 day-prognosis and ICU-acquired infections among critically ill patients of community-acquired severe sepsis with new onset.

For community-acquired severe sepsis group:

Inclusion Criteria:

• at least 18 years of age and no more than 90 years of age
• sepsis was defined according to consensus criteria
• diagnosis of sepsis and complicatied with organ dysfunction no longer than 48 h
• provided written informed consent.

Exclusion Criteria:

• diagnosis of hematological,immunological disease or cancer
• treatment with chemotherapy agents or corticosteroids within 6 months prior to or during the hospitalization

For non-severe sepsis ICU control group:

Inclusion Criteria:

• at least 18 years of age and no more than 90 years of age
• without diagnosis of sepsis and admitted to ICU
• provided written informed consent.

Exclusion Criteria:

• diagnosis of hematological,immunological disease or cancer
• treatment with chemotherapy agents or corticosteroids within 6 months prior to or during the hospitalization

For healthy control group:

Inclusion Criteria:

• at least 18 years of age and no more than 90 years of age
• provided written informed consent.

Exclusion Criteria:

• diagnosis of hematological,immunological disease or cancer
• treatment with chemotherapy agents or corticosteroids within 6 months prior to enrollment

We enroll patients with community-acquired severe sepsis and then the patients admitted to ICU without the diagnosis of severe sepsis as ICU control group, and the heathy volunteers as healthy control group.