The Isolation of a Serum Lipid Which Inhibits Serologic Reactions

Conclusions and Summary The inhibitory activity of the human plasma fraction IV-1, remains unaffected by extraction with ether but disappears after subsequent extraction with ethanol. It has been possible to isolate from the ethanol extract an active inhibitory fraction which by its solubility behavior in acetone, CdCl2 and BaCl2, and by its nitrogen/phosphorus ratio, has been identified as a human serum lecithin. Quantitative serologic titrations have shown that this human serum lecithin fraction exerts inhibitory activity toward euglobulin fractions of biologic false positive origin in appreciably lower concentrations than does the whole serum fraction IV-1. However, comparative measurements have indicated that the inhibitory activity of the latter is more specific than that of the former, as evidenced by their respective actions toward euglobulin fractions of syphilitic origin. It appears, therefore, that the specificity of the whole fraction IV-1 may be attributed to the firm combination of the serum lecithin with the protein. While egg lecithin has no specific inhibitory activity, purified beef heart lecithin exhibits the same inhibitory pattern as human serum lecithin.</jats:p