C5a-inhibitor deficiency in peritoneal fluids from patients with familial Mediterranean fever.

Normal peritoneal fluid contains an inhibitor of neutrophil chemotaxis that acts by antagonizing the complement-derived chemotactic anaphyllatoxin C5a. The inhibitor resembles a substance previously described in synovial fluids and is a protein with a molecular weight of approximately 40,000 as determined by gel filtration. In contrast, levels of inhibitory activity in peritoneal fluids from five patients with familial Mediterranean fever were decreased to less than 10 per cent of those found in normal subjects. Gel filtration of peritoneal and synovial fluids from these patients did not yield any fraction with inhibitory activity. We suggest that C5a-inhibitor deficiency in joint and peritoneal fluids from patients with familial Mediterranean fever may have a role in the pathogenesis of the inflammatory attacks characteristic of this disease.