The Activating Effect of Calcium on a Bactericidal Substance for Bacillus Subtilis in Human Serum

An enhanced bactericidal activity of human serum for B. subtilis develops during many different forms of illness, e.g. carcinoma, virus and bacterial infections, and during acute coronary occlusion. This increased bactericidal effect cannot be related to leucocytosis, fever, serum complement, C-reactive protein, or a specific antibody reaction. The serum bactericidal factor becomes inactive in decalcified serum, but active again when optimal concentrations of calcium are added. Magnesium does not cause reactivation.