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A Dancis, C Ehmann, R Ferziger, K Grima and S Karpatkin
Department of Medicine, New York University Medical School 10016.
The mol wt of the glycoprotein(s) carrying the PLA1 antigen was examined on
platelets, megakaryocytes and endothelial cells by immunoblotting with a
human polyclonal anti-PLA1 antibody (BE), as well as on four different
monoclonal antibodies (MoAbs; DEK-1, DEK-2C, DEK- 10, and DEK-16) raised
against GPIIIa, the 100,000-mol wt platelet glycoprotein known to carry the
PLA1 antigen. BE reacted with PLA1 positive but not with PLA1 negative
platelets. DEK-1 reacted strongly with PLA1 positive platelets but weakly
with PLA1 negative platelets. The remaining three MoAbs reacted equally
with PLA1 positive as well as negative platelets. BE, DEK-1, DEK-10, and
DEK-16 reacted with a 120,000- as well as 100,000-mol wt band on immunoblot
of PLA1 positive platelets. The 120,000-mol wt band copurified with
affinity purified 100,000-mol wt GPIIIa. Megakaryocytes had a prominent
120,000- as well as 105,000-mol wt band that reacted with BE on immunoblot
(the 100,000- mol wt band was not detectable). Umbilical cord endothelial
cells from presumed PLA-positive infants had a prominent 100,000-mol wt
band that reacted with BE, DEK-16, and DEK-1 (the 120,000-mol wt band was
not visualized). The 120,000- and 100,000-mol wt PLA1-positive bands could
be digested with proteolytic enzymes to 55,000- to 65,000-mol wt- resistant
fragments that retain PLA1 epitopes. Further digestion with
endoglycosidase-H lowered the apparent mol wt by approximately 2,000 to
6,000 daltons without affecting PLA1 reactivity. We conclude that the PLA1
antigen is present on a 120,000- as well as 100,000-mol wt glycoprotein of
platelets and megakaryocytes, a 105,000-mol wt band of megakaryocytes, and
a 100,000-mol wt glycoprotein of endothelial cells. We postulate that the
120,000-mol wt glycoprotein, which shares three or more epitopes with the
100,000-mol wt GPIIIa, may be a post- translational precursor of this
species.
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| Copyright © 1988 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||