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Increased platelet sensitivity to ristocetin is predicted by the binding characteristics of a GPIb/IX determinant
Author(s) -
Miller Jonathan L.,
Hustad Kent O.,
Kupinski John M.,
Lyle Vicki A.,
Kunicki Thomas J.
Publication year - 1990
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/j.1365-2141.1990.tb02589.x
Subject(s) - platelet , ristocetin , platelet glycoprotein gpib ix complex , chemistry , platelet membrane glycoprotein , monoclonal antibody , epitope , immunofluorescence , microbiology and biotechnology , von willebrand factor , trypsin , von willebrand disease , antibody , immunology , biochemistry , medicine , biology , enzyme
Summary Platelets from patients with platelet‐type von Willebrand disease (vWD) were used as immunogens for the production of murine monoclonal antibodies (MoAbs). One such MoAb, C‐34, inhibited ristocetin‐induced aggregation of patient or normal platelets. but not aggregation induced by other aggregating agents. As demonstrated by crossedimmunoelectrophoresis, C‐34 recognized an epitope within the GPIb/IX complex. In indirect immunofluorescence studies on fresh platelets, the ratio of any of four different anti‐GPIb MoAbs to one another was near unity (0.88‐1.14) both for normals and for patients. In contrast, the ratio of the binding of C‐34 to such a MoAb (AP‐1) was 0.31 ± 0.02 ( x ± SE) for normal platelets and significantly increased to 0.54 ± 0.01 for patient platelets ( P < 0.001). In NP‐40 lysates of 3 H‐labelled platelets, saturating concentrations of C‐34 produced much fainter bands than did AS‐2 or other anti‐GPIb MoAbs in the GPIb and GPIX regions. In contrast to the other anti‐GPIb MoAbs. C‐34 did not bind to the purified 125 I‐Iabelled glycocalicin fragment of GPIb, to the glycocalicin derivative identified by crossed‐immunoelectrophoresis, or to the amino‐terminal ˜ 40 kDa portion of GPIbα cleaved from 3 H‐labelled platelets by trypsin. C‐34 appears to be the first MoAb that is quantitatively informative in identifying the abnormal platelets in platelet‐type vWD. The observed differences between the patient and normal platelets may reflect an abnormality in the primary structure of the GPIb/ IX complex. Alternatively, patient platelets may have an abnormality of other structures near this region that impose less of a steric hindrance upon binding of antibody to the C‐34 epitope.