MONOCLONAL MYELOMATOUS IGA WITH ANTI-LIPOPROTEIN ANTIBODY-ACTIVITY OF RA SPECIFICITY

  • 1 January 1979
    • journal article
    • research article
    • Vol. 21  (2) , 171-183
Abstract
Investigations performed in a patient with myeloma, hyperlipidemia and xanthomatosis demonstrated the antilipoprotein activity of the monoclonal IgA directed against an antigenic site, called Ra, to be different from those previously described. A complex IgA .beta.-lipoprotein was first characterized. After isolation and purification of the IgA, the association between IgA and lipoprotein was apparently immunologically mediated. The antibody is an IgA .lambda. bound via its Fab portion and in fixed combining ratio to an antigenic determinant shared only by LDL [low density lipoprotein] and VLDL [very low density lipoprotein] of humans and some other mammalians to the exclusion of any other serum proteins. Passive hemagglutination and inhibition of hemagglutination tests suggested that the antigenic site Ra is not located on apoprotein B (major proteic moiety of LDL and VLDL), since the antigenic determinants of apolipoproteins are different in humans and in animals and since IgA Ra failed to react with apolipoprotein B obtained by delipidation of LDL. The lack of reaction between IgA Ra and HDL [high density lipoprotein] suggested that the antigenic determinant is not only present on the lipid hapten, such as in the case of PG and AS determinants which are located on VLDL, LDL and HDL from humans and animals. The antigenic determinant revealed by IgA Ra is apparently different from those previously described.