Replacement of Magnesium by Cobalt and Manganese in the Interactions of the Properdin System with Bacteria and with Zymosan

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Abstract
Summary: A study has been made of the functional replacement of Mg++ by other cations in the interactions of properdin and complement with bacteria and with zymosan. Of 22 cations tested, only Mg++, Co++ and Mn++ were able to restore bactericidal activity to serum that had been treated with cation-exchange resin. Mg++ was quantitatively the most effective, being twice as active as Co++ and five times as active as Mn++ on a molar basis. Ca++ was completely inactive. Mg++, Co++ and Mn++, when added to resintreated serum at levels that effectively restored bactericidal activity, also restored the ability of the serum to form a properdin-zymosan complex with zymosan at 17°. However, only Mg++ and Co++ restored to resin-treated serum the property of rendering C′3 susceptible to inactivation by zymosan at 37°C. These findings point out differences between the mechanism of the bactericidal activity of the properdin system and the inactivation of C′3 by zymosan.