High glucose removes natural anti-α-galactoside and anti-β-glucoside antibody immune complexes adhering to surface O-glycoproteins of normal platelets and enhances platelet aggregation.

Human natural anti-α-galactoside (anti-Gal) and anti-β-glucoside (ABG) antibodies were previously reported to recognize the serine- and threonine-rich peptide sequences (STPS) of albumin-associated O-glycoproteins (AOP1 and AOP2) as surrogate antigens, forming anti-Gal/ABG-AOP1/AOP2-albumin triplet immune complexes in plasma. Since antibodies in these triplets still possessed unoccupied binding sites, the presence of triplets on human platelets that abound in surface O-glycoproteins was examined. Upon treatment with α-galactosides and β-glucosides, normal platelets freshly isolated from young healthy individuals released triplets identical with plasma triplets according to ELISA results.

Circulating Lp(a):LDL complexes contain LDL molecules proportionate to Lp(a) size and bind to galectin-1: a possible route for LDL entry into cells.

The molecular mechanism of vascular pathology mediated by circulating lipoprotein(a) [Lp(a)] remains unknown. We examined the role of two distinguishing features of Lp(a) viz non-covalent complex formation with a low density lipoprotein (LDL) and heavy glycosylation as determinants of binding of this lipoprotein and its LDL complex to cell-surface receptors. LDL isolated from the Lp(a):LDL complex, free LDL and oxidized LDL were equally efficient in forming a reconstituted complex with pure Lp(a).

Human plasma anti-α-galactoside antibody forms immune complex with autologous lipoprotein(a).

Anti-α-galactoside antibody (anti-Gal) from human plasma that bound to α-galactoside-bearing guar galactomannan gel and was eluted with specific sugar (affinity-purified anti-Gal ; APAG) invariably contained apo(a) and apo B subunits in a proportion close to that in plasma lipoprotein(a) [Lp(a)]. Since LDL does not contain apo(a), result suggested Lp(a) as a component of APAG. Lp(a) in APAG was complexed with anti-Gal since plate-coated anti-apo(a) captured Lp(a) along with the antibody.