A Lipid-Protein Fraction in Rheumatoid Plasma Precipitable With Chondroitin Sulfate After Euglobulin Removal*

Abstract

Acid mucopolysaccharides of human plasma have been observed ( 1 ) to vary as do acute phase reactants, i.e., to increase nonspecifically in any inflammatory state. The euglobulin fraction itself with which the acid mucopolysaccharides were associated increased also in such circumstances. On later comparing levels of acid mucopolysaccharides in samples of serum and plasma drawn simultaneously, it was noted that the acid mucopolysaccharides measurable in the euglobulin fraction were derived at least in part from the formed elements of blood during blood clotting (2). It seemed possible, therefore, that the amount of plasma protein precipitable as euglobulins by dilution at pH 5.8 might increase in inflammation as a result of the release of acid mucopolysaccharides into the blood, causing alteration of isoelectric point of plasma proteins already present. Precedent for such a possibility has been well established by the earlier observations of other investigators on the interactions of fibrinogen and ,8-lipoproteins and polyanions (3, 4). The possibility as it relates to rheumatoid plasma was mentioned in effect also bv Badin, Schubert and Vouras (5).To explore this possibility, studies were carried out on the interaction of chondroitin sulfate with the proteins remaining in plasma after isoelectric precipitation of spontaneously occurring euglobulins by dilution with mineral acid to pH 5.8. The additional protein available for precipitation under identical conditions of dilution and pH on addition of chondroitin sulfate (the fraction being called Sj) was strikingly increased by prior dialysis of the plasma against balanced bufferred salt solution. This increase was prevented if a heat-resistant, organic, dialyzable factor present in a pressure dialy-sate of plasma was restored