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

Whole serum complement (CH50) and C3, C4, and C3PA plasma values were studied in 48 patients: 9 with nonseptic shock; 20 with sepsis; 14 with septic shock caused by gram-negative bacteria; 5 with septic shock caused by gram-positive bacteria. All were compared with a control group of 25 healthy individuals. Determinations were made upon admission and again 48 and 96 h later. No significant differences in complement values were found between the patients with nonseptic shock and the control group. In the patients with sepsis, decreased CH50 (p less than 0.001) and increased C3PA (p less than 0.02) values were observed, while C3 and C4 remained unaltered. In the patients with septic shock, markedly decreased levels of CH50, C3, and C4 were seen (p less than 0.001, and p less than 0.001, and p less than 0.001, respectively) without changes in C3PA levels. There were no differences between septic shock due to gram-negative and gram-positive bacteria, or between patients who died and those who survived. After 96 h, the altered values returned to the normal range. This underlines the transitory activation of the complement system through the classic pathway and suggests its possible role in the pathogenesis of septic shock in man.