Complement-Mediated Early Clearance of Haemophilus influenzae Type b from Blood is Independent of Serum Lytic Activity

Abstract

The role of complement-mediated serum lytic activity in the clearance of encapsulated Haemophilus influenzae type b was studied by comparing clearance of bacteria from blood in normal mice with that in congeneic C5-deficient animals and mice depleted of complement by using cobra-venom factor. The clearance of organisms from blood by C5-deficient and C5-sufficient normal animals was similar. C3 depletion and the inability to fix C3 to the surface of bacteria were, however, associated with impaired clearance of organisms during the first 24 h after intravenous bacterial challenge. These studies suggest that complement-mediated opsonization rather than bacteriolysis is important in determining early clearance of H. influenzae type b from the bloodstream.

The Role of C3 in Mediating Binding and Ingestion of Group B Streptococcus Serotype III by Murine Macrophages

“…C3-dependent binding may be important in determining mononuclear phagocyte-dependent clearance of these pathogens from blood, particularly in patients with little or no type-specific serum antibody. (Pediatr Res 30: 118-123,1991) Abbreviations CR3, complement receptor type 3 Ni-S, nonimmune serum Im-S, immune serum CoVF, cobra venom factor PB, phagocytosis buffer i.p., intraperitoneal HBSS, Hanks' balanced salt solution role with encapsulated pneumococci and Haemophilus influenzae has underscored that complement-mediated phagocytosis is important in defending against these pathogens (2)(3)(4)(5)(6). These studies are consistent with the hypothesis that clearance of complement-opsonized bacteria from the circulation by mononuclear phagocytes composing the reticuloendothelial system is essential in defending against bacteremia and in preventing disseminated infection.…”

“…Serum was heat-inactivated by incubation for 60 rnin at 56°C. This serum had no functional complement activity as measured by C3 fixation to rabbit red blood cells (6).…”

“…Serum was obtained from CDF-1 mice as previously described (6). Ni-S was obtained from adult CDF-1 mice (20-25 g; Charles River Breeding Laboratories, Wilmington, MA).…”

“…inoculation. Serum obtained from these animals had no detectable C3 fixation titer (s1:2) and had less than 20 mg/dL of C3 as determined by a radial immunodiffusion method (6). Serum was heat-inactivated by incubation for 60 rnin at 56°C.…”

lgtC Expression Modulates Resistance to C4b Deposition on an Invasive Nontypeable Haemophilus influenzae

“…It has been demonstrated that C5-knockout mice are not more susceptible to H. influenzae type b bacteremia when compared with syngenic mice with normal C5 levels (28), and that both mutant and wild-type animals can eradicate the infection at approximately equivalent rates. In contrast, mice depleted of C3 had significantly impaired clearance of both H. influenzae type B (Hib) (13) and NTHi (15).…”