C5b-7 and C5b-8 precursors of the membrane attack complex (C5b-9) are effective killers of E. coli J5 during serum incubation.
The finding that C9-deficient sera (C9D) can kill serum sensitive strains of Gram-negative bacteria by us and other investigators, questions the role of C9 in the membrane attack complex as necessary for cell death. In these studies we have demonstrated that C5b-8 complexes generated on E. coli J5 during incubation in C9-depleted and C9-neutralized sera are effective in killing Gram-negative bacteria. In the same study, we extended our investigations to show that the deposition of C5b-7 complexes (from C8-deficient [C8D], C8 depleted and C8-neutralized sera) is also effective in killing Gram-negative bacteria. In all cases, these studies demonstrated that when E. coli J5 was incubated with C8D, C9D and pooled normal human serum [PNHS], deposited C5b-9 complexes from PNHS produced more killing than C5b-7 or C5b-8 complexes alone. These experiments clearly demonstrated that C5b-7 and C5b-8 complexes are bactericidal and that multimeric C9 within C5b-9 is not an absolute requirement for inner membrane damage and cell death of Gram-negative bacteria.
Bloch
E F
EF
Department of Microbiology, Howard University College of Medicine, Washington, D.C., USA.
Knight
E M
EM
Carmon
T
T
McDonald-Pinkett
S
S
Carter
J
J
Boomer
A
A
Ogunfusika
M
M
Petersen
M
M
Famakin
B
B
Aniagolu
J
J
Walker
J
J
Gant
R
R
Walters
C S
CS
Gaither
T A
TA
D001770:Blood Bactericidal Activity; D015169:Colony Count, Microbial; D003182:Complement C5 / Q000276:immunology*; D003185:Complement C8 / Q000172:deficiency; D015938:Complement Membrane Attack Complex / Q000276:immunology*; D003165:Complement System Proteins / Q000276:immunology*; D004926:Escherichia coli / Q000276:immunology*; D006801:Humans; D066298:In Vitro Techniques; D009500:Neutralization Tests
D003182:Complement C5; D003185:Complement C8; D015938:Complement Membrane Attack Complex; C042295:complement C5b-8 complex; C037453:complement C5b-7 complex; D003165:Complement System Proteins