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), the Second (C2) and the Fourth (C4) Component of Complement with Different Preparations of Bacterial Lipopolysaccharides and with Lipid AInstitute of Medical Microbiology, Johannes Gutenberg University, 65 Mainz, Germany
Abstract
Lipopolysaccharides of Gram-negative bacteria (LPS) known to activate the complement system via the alternate pathway bypassing C
, C4, and C2 had a direct effect on purified C
, but no effect on purified C4 and C2. These studies were performed with different preparations of LPS and of Lipid-A isolated from smooth (S-) and rought (R-) forms of Escherichia coli and Salmonella strains. It was shown that the effect of LPS on C
depends upon the concentration and type of LPS applied: 0.77 µg of LPS from E. coli 0 75, 2.5 µg of LPS from S. minnesota R 595, 24 µg of Lipid-A and 55 µg of Lipid-A/BSA were necessary to get 50% inhibition of free C
. In contrast, 100 µg of LPS from E. coli 0 111, from S minnesota S-form, or from S. minnesota R 345 showed no significant inhibition. Binding of C
to EA or EAC4 markedly reduced the effect of LPS and of Lipid-A on C
. The inhibition of C
was shown to be the result of a direct interaction of LPS and of Lipid-A with the C1 subunit C1q: LPS precipitated C1q. LPS and Lipid-A had no effect on the C1 esterase activity against C2.
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