Effect of hog anaphylatoxin (C5a) on vascular permeability and leukocyte emigration in vivo

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Abstract
The effects of highly purified hog anaphylatoxin (C5a) in leukocyte emigration were investigated in guinea pigs in vivo using two experimental models: Subcutaneous infusions. Sterile solutions of C5a in saline infused at a rate of 1.8 μg C5a/h (0.2 ml/h) for 10h induced a dense accumulation of leukocytes, mainly neutrophils but also some eosinophils at the site of application. In control infusions with saline alone comparatively few leukocytes were found. Single injections into the pleural cavity. 10 or 20 μg C5a (dissolved in 2 ml saline) caused a dosedependent increase in leukocyte number and volume of pleural exudate. Bradykinin in a dose of 18 μg produced similar fluid exudation as 20 μg C5a but had no significant effect on leukocyte accumulation. Intrapleural injections of C5a further caused the appearance of i.v. injected Evans blue in the pleural cavity. This effect, indicating an increase in vascular permeability lasted for about 3 h. Since at least one of the two models used — subcutaneous infusion—simulates natural conditions—continuous local generation of C5a in small amounts at the site of an inflammatory lesion—the results indicate that C5a once formed by complement activation in natural defense reactions may contribute to local increase in vascular permeability and leukocyte infiltration.