In vivo evidence that an intact lytic complement pathway is not essential for successful removal of circulating Borrelia turicatae from mouse blood.

Complement component C5-deficient mice were found to be able to eliminate blood-borne Borrelia turicatae as effectively as normocomplementemic control animals. The absence of C5 and the resultant loss of hemolytic complement activity were confirmed for the deficient mouse strains used. Immunofluorescent staining of complement component C3 on blood-derived borreliae could be readily accomplished as early as 2 days before spirochetal elimination from all mice tested. These observations would suggest that C3 deposition was occurring, even though the terminal lytic steps were blocked in the complement-deficient mice. We propose that spirochetolysis is not requisite for successful removal of borreliae from the circulation of mice.