The use of hemolysin inhibition in the study of experimental and clinical hyperlipemia; the non-specific inhibition of streptolysin O, by serum lipoproteins.

Streptolysin 0 is one of a group of hemolytic toxins that have in common the property of being inhibited by cholesterol. This property is also shared by saponin, a hemolytic agent of quite a different type. Other hemolytic toxins, such as streptolysin S, are not inhibited by cholesterol but are neutralized by phospholipids (1-3). Certain observations suggest that the inhibition of these hemolysins by serum is influenced by the physicochemical state of serum lipoproteins. For example, the cholesterol contained in normal human and animal sera does not inhibit streptolysin O hemolysis. Old samples of sera, or sera contaminated by certain strains of bacteria, do become strongly inhibitory, however (2). Under these conditions the serum cholesterol is presumably liberated from lipoprotein complexes. Streptolysin S has been shown to be inhibited by serum lipoproteins. This inhibition may be varied by measures which alter the native state of these proteins or by diseases which are associated with disturbances in lipid metabolism (4-8). Also, the inhibition of saponin hemolysis by whole plasma is not a simple function of the concentration of its lipid components. The sum of the inhibition produced by each of the lipid and protein components of plasma is not as great as the inhibition of saponin hemolysis by whole plasma (9). These and other observations suggest that further study of hemolysin inhibition by sera of abnormal lipid composition may detect changes in lipoproteins in intact serum which may not be readily revealed by conventional analytical methods. This report describes the inhibition of two cholesterol sensitive hemolysins, streptolysin 0