Activation of the alternative (properdin) pathway by divalent cations.

Mg++, Mn++ and Co++ activate the C system as judged by the reduction in cobra venom factor indeed hemolysis, and cleavage of properdin factor B and C3. The maximum effect requires the addition of 5 to 10 mM of these cations to dialyzed sera respond in similar fashion indicating that these divalent cations can trigger the alternative pathway without the addition other activating agents.