Abstract
Summary
A simple technic is described for separating streptolysin O inhibitor from the plasma of mice made refractory to the lethal effect of streptolysin O. Results of fractination and subsequent analysis indicate that the bulk of the inhibitory activity of refractory mouse plasma is associated with a lipoprotein of extremely low density (< 1.006) containing abundant lipid relative to protein. All classes of serum lipids are represented in the inhibitor-rich fraction; their concentrations, as well as the concentration of protein, are significantly greater than values obtained for comparable fractions from normal mouse plasma. Esterified cholesterol shows the greatest increment and seems most closely to parallel the inhibitory activity. It is suggested that the capacity of the induced lipoprotein to inhibit streptolysin O depends on an abundant content and unique orientation of lipids that are capable of interacting with the toxin.
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