Hemolytic complement titers and complement C3 levels in endotoxin-induced mastitis.

Escherichia coli lipopolysaccharide B was instilled through the lactiferous duct of cows to induce acute mastitis. Hemolytic complement (C) activity and C3 concentrations were determined in blood serum and in renninprecipitated whey before, and at certain times after, mastitis was induced. Hemolytic complement activity was detected in the whey only during the first 36 hours after endotoxin was instilled, whereas activity was not seen before and 48 or more hours after the endotoxin was given. The maximum titer as measured with the guinea pig RBC/bovine natural antibody system was 1:64. The C3 concentrations in normal whey (before installation of endotoxin), measured by radial immunodiffusion, were between 1% and 4% of the base-line blood serum values (pool from healthy cows). The whey concentration of C3 increased (to 5% to 18%) during the first 8 hours of mastitis. However, at 72 hours, the whey values were back to preinstillation concentrations in all quarters.