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Measurement of Platelet Surface‐Bound IgG by a Monoclonal 125 I‐Anti‐IgG Assay
Author(s) -
Court Wayne S.,
LoBuglio Albert F.
Publication year - 1986
Publication title -
vox sanguinis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.68
H-Index - 83
eISSN - 1423-0410
pISSN - 0042-9007
DOI - 10.1111/j.1423-0410.1986.tb04869.x
Subject(s) - platelet , microbiology and biotechnology , chemistry , immunoglobulin g , monoclonal antibody , antibody , immunoglobulin fab fragments , lysis , immunology , biochemistry , biology , complementarity determining region
. We have described the use of a monoclonal 125 I‐labeled anti‐IgG ( 125 I‐MA) to assay IgG antibody displayed on the surface of platelets from normal and immune thrombocytopenic patients and reported levels of IgG 10–100‐fold lower than previous studies. This report describes the immunologic characteristics of the 125 I‐MA and the assay for surface IgG. The 125 I‐MA has a high binding affinity for surface‐displayed IgG (2.22 times 10 9 M ‐1 ), reacts equally well with all four subclasses of IgG and not at all with IgM or IgA. In our assay, the binding of I25 I‐MA was found to be ≥99% specific for IgG (no nonspecific association of I25 I‐MA with platelets) and the binding ratio of I25 I‐MA to IgG displayed on the cell surface was 0.91 (close to unity). Finally, platelet lysates were found to contain large amounts of IgG protein (39,597 ± 27,418 molecules/platelet) as compared to surface‐displayed IgG (124 ± 86 molecules/platelet). This assay has excellent characteristics for quantitation of IgG on platelets and the discrepancy with other techniques may, in part, be due to intentional or inadvertent lysis of platelets during assay conditions.