Involvement of the lectin pathway of complement activation in antimicrobial immune defense during experimental septic peritonitis.
A critical first line of defense against infection is constituted by the binding of natural antibodies to microbial surfaces, activating the complement system via the classical complement activation pathway. In this function, the classical activation pathway is supported and amplified by two antibody-independent complement activation routes, i.e., the lectin pathway and the alternative pathway. We studied the contribution of the different complement activation pathways in the host defense against experimental polymicrobial peritonitis induced by cecal ligation and puncture by using mice deficient in either C1q or factors B and C2. The C1q-deficient mice lack the classical complement activation pathway. While infection-induced mortality of wild-type mice was 27%, mortality of C1q-deficient mice was increased to 60%. Mice with a deficiency of both factors B and C2 lack complement activation via the classical, the alternative, and the lectin pathways and exhibit a mortality of 92%, indicating a significant contribution of the lectin and alternative pathways of complement activation to survival. For 14 days after infection, mannan-binding lectin (MBL)-dependent activation of C4 was compromised. Serum MBL-A and MBL-C levels were significantly reduced for 1 week, possibly due to consumption. mRNA expression profiles did not lend support for either of the two MBL genes to respond as typical acute-phase genes. Our results demonstrate a long-lasting depletion of MBL-A and MBL-C from serum during microbial infection and underline the importance of both the lectin and the alternative pathways for antimicrobial immune defense.
Department of Immunology, University of Regensburg, F.-J.-Strauss-Allee, D-93042 Regensburg, Germany.
Michaela
M
Windbichler
Bernd
B
Echtenacher
Thomas
T
Hehlgans
Jens C
JC
Jensenius
Wilhelm
W
Schwaeble
Daniela N
DN
Männel
D000818:Animals; D001424:Bacterial Infections / Q000276:immunology* / Q000401:mortality; D002432:Cecum; D015169:Colony Count, Microbial; D003167:Complement Activation; D015922:Complement C1q / Q000172:deficiency; D003175:Complement C2 / Q000172:deficiency; D011415:Complement Factor B / Q000172:deficiency; D003170:Complement Pathway, Alternative; D008026:Ligation; D008099:Liver / Q000382:microbiology; D037601:Mannose-Binding Lectin / Q000276:immunology*; D051379:Mice; D010538:Peritonitis / Q000276:immunology* / Q000401:mortality; D011677:Punctures; D018805:Sepsis / Q000276:immunology* / Q000401:mortality; D013154:Spleen / Q000382:microbiology
D003175:Complement C2; D037601:Mannose-Binding Lectin; D015922:Complement C1q; D011415:Complement Factor B