Soluble membrane attack complex in ascites in patients with liver cirrhosis without infections

To study complement activation in 46 patients with alcoholic cirrhosis and ascites but no spontaneous bacterial peritonitis (SBP) and 10 healthy controls.

Complement activation was determined by the measurement of soluble membrane attack complex (sMAC) concentrations in ascites and plasma. In patients, metabolic liver function was determined by the galactose elimination capacity and the clinical status assessed by the Model of End-Stage Liver Disease and Child-Pugh scores.

Ascites sMAC levels were markedly higher than in the corresponding plasma sample (median (range): 596 (170 - 1519) vs 160 (77 - 848) μg/L; P < 0.01). Ascites sMAC levels correlated positively with liver status. There was no relationship between ascites sMAC and leukocyte count. No relationship between ascites sMAC and blood C-reactive protein, albumin or neutrophile count was found. Plasma sMAC concentrations were slightly higher in patients than in controls [130 μg/L (70 - 204); P = 0.04]. Neither sMAC in ascites nor plasma was related to mortality.

The increased sMAC concentration in ascites and plasma indicate an activation of the complement system in cirrhosis even in the absence of SBP. This was particularly evident in the peritoneal fluid and most marked in patients with preserved liver status. The high ascites sMAC levels may reflect transudation of membrane attack complexes from the liver. Whether this complement activation has any clinical implications remains to be clarified.