Generation and degradation of the complement fragment C5a in human serum by Bacteroides gingivalis.

Abstract

The ability of Bacteroides gingivalis to generate chemotactic activity and the complement fragment C5a in human serum was assayed. When fresh serum was incubated with B. gingivalis there was a rapid increase of chemotactic activity of the serum during the first 15 min, but longer incubation resulted in loss of chemotactic activity. When heat‐inactivated serum was incubated with B. gingivalis similar increase and decrease of the chemotactic activity of serum was also observed. The chemotactic peptide C5a could be demonstrated in all sera showing chemotactic activity. The generation of C5a and possibly also other chemotactic substances in heat‐inactivated serum by B. gingivalis may mean that this chemotactic activity was formed from serum proteins by the proteolytic activity of B. gingivalis. The proteolytic activity of B. gingivalis may also be responsible for the inactivation of C5a generated in serum.