IMMUNOCHEMICAL STUDY OF LIPOPROTEIN SUBSTANCE PG

  • 1 January 1977
    • journal article
    • research article
    • Vol. 25  (5) , 333-340
Abstract
Site Pg is an antigenic determinant which is present on the surface of serum lipoproteins and reacts with [human] antilipoprotein myelomatous immunoglobulin [Ig], the IgA Ger. Site Pg is extracted from LDL [low density lipoproteins] by a 6% ether-methanol mixture. The organic substrate is evaporated under vacuum and dissolved in saline before being submitted to an extraction using ether. Under these conditions, site Pg remains in the aqueous phase. A polyacrylamide gel filtration on Biogel P2 permits separation of the substance which reacts with IgA Ger. anti-Pg from the aqueous phase. The identification of site Pg demonstrated the presence of galactose, phosphorus and choline. Site Pg had a MW of 330. The reactivity of site Pg with IgA anti-Pg was measured by inhibition of passive hemagglutination and fluorescence quenching. The association constants of site Pg with IgA Ger. or with its Fab fragment could be calculated (1.6 105 M-1 with the whole IgA ; 2.3 105 M-1 with the Fab fragment). If phosphorylcholine plays an immunodominant role, the presence of sugar seems necessary, since the association constant of the whole IgA Ger. with site Pg is higher than that of IgA Ger. with phosphorylcholine alone.

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