The effect of divalent cation chelators and magnesium on activation of the alternative complement pathway by Fusobacterium polymorphum (nucleatum)

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Abstract
A complement consumption assay was used to investigate the anti‐complementary activity (AC) of Fusobacerium polymorphum (nucleateum) in guinea pig complement (GPC) which had been treated with the divalent cation chelators ethylamine diamine tetra acetic acid (EDTA) or ethylene glycol tetra acetic acid (EGTA). In the presence of 1 mM EGTA, a cell wall preparation of F. polymorphum reduced the hemolytic complement activity of GPC to essentially the same degree as that observed in the non‐chelated serum controls.hemolysin sensitized sheep erythrocytes (EA). A 1 mM concentraction of EDTA inhibited both the AC activity of F. polymorphum cell wall and the lysisi of EA via the classical pathway. It was also shown that the addition of 1 mM magnesium ion(Mg++)reversed the inhibitory effects of 1 mM EDTA on the lysis EA and on the apparent alternative pathway acitivity displayed by F. polymorphum cell walls. In contrast, the same concentration of Mg++ in the 1 mM EGTA tests did not reverse the EGTA inhibition of the classical pathwaym nor did it markedly augment the alternative pathway. These results indicate that the observed AC activity demonstrated by the cell wall preparation of F. polymorphum did not depend upon a functional classical pathway, but that it porbably occurred exclsively via the alternative complement pathway.

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