Complement activation in septic shock due to gram-negative and gram-positive bacteria

Area of Science:

• Immunology
• Critical Care Medicine

Background:

• The complement system plays a crucial role in innate immunity and inflammation.
• Sepsis and septic shock involve complex immune dysregulation.
• Understanding complement system's role in sepsis is vital for treatment strategies.

Purpose of the Study:

• To investigate the behavior of complement system components (CH50, C3, C4, C3PA) in patients with sepsis and septic shock.
• To compare complement levels between nonseptic shock, sepsis, septic shock, and healthy controls.
• To determine if complement activation differs based on the causative pathogen (gram-negative vs. gram-positive) or patient outcome.

Main Methods:

• Serum complement (CH50) and plasma complement components (C3, C4, C3PA) were measured in 48 patients and 25 healthy controls.
• Measurements were taken on admission and at 48 and 96 hours post-admission.
• Statistical analysis was performed to compare complement levels across groups and over time.

Main Results:

• No significant differences in complement values were found between nonseptic shock patients and controls.
• Sepsis patients showed decreased CH50 and increased C3PA, with normal C3 and C4.
• Septic shock patients exhibited markedly decreased CH50, C3, and C4 levels, with unchanged C3PA. These alterations normalized by 96 hours.

Conclusions:

• The complement system, particularly the classic pathway, is transiently activated in septic shock.
• Complement activation may play a role in the pathogenesis of human septic shock.
• The observed complement changes were similar regardless of bacterial type or patient survival.