Platelet-bound and plasma triplets are identical
Platelets deprived of their attached triplets by treatment with a
mixture of anti-Gal- and ABG-specific sugars (denuded platelets) were
treated with FITC-labeled anti-Gal or with plasma triplets reconstituted
using FITC-labeled albumin, anti-Gal and a mixture of AOP1 and AOP2.
Plasma anti-Gal alone as well as reconstituted plasma triplets were
captured by denuded platelets unless inhibited by specific sugars. In
contrast, native platelets captured significantly less of both (Fig.3).
As reconstituted plasma triplets added to denuded platelets bore their
FITC label on albumin and their attachment to these platelets were
inhibited by antibody-specific sugars the above result confirmed that
antibody-O-glycoprotein-albumin triplets anchor on platelets using the
unutilized binding sites available on their antibodies. Since triplets
from cell-free plasma could substitute for platelet-bound triplets and
O-glycoproteins of plasma and platelet triplets were equal, both in
alkaline gel electrophoretic mobility and in O-glycan content, it seemed
reasonable to conclude that triplets, in free form in plasma or bound to
platelets, were identical and consisted of albumin and either anti-Gal
or ABG linked by AOP1 or AOP2 which acts as bridging molecule as
demonstrated in the case of plasma triplets [1]. Distribution of
triplets between platelets and cell-free plasma shows that triplets of
both anti-Gal and ABG are born more by platelets than by free plasma in
same blood volume (Fig.3 inset). This structure of the triplets adhering
to circulating platelets is in agreement with an earlier report that the
amounts of albumin and immunoglobulin on platelet surface are positively
correlated [18].