Biomaterial Database

Extracellular epitopes of platelet glycoprotein Ib alpha reactive with serum antibodies from patients with chronic idiopathic thrombocytopenic purpura. 1995

R He, and D M Reid, and C E Jones, and N R Shulman

Clinical Hematology Branch, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-1370, USA.

Glycoproteins (GPs) IIb/IIIa and Ib/IX are principal targets of autoantibodies (autoAbs) in idiopathic thrombocytopenic purpura (ITP). Platelet-associated Abs against GPIIb/IIIa primarily recognize discontinuous or nonlinear epitopes (Fujisawa et al, Blood 81:1284, 1993). This study focused on whether Abs against the extracellular domain of GPIb/IX might react with short linear amino acid (aa) sequences of GPIb alpha. Complementary DNAs (cDNAs) coding for two overlapping fragments of GPIb alpha were amplified, cloned into pFLAG.2 plasmids, and expressed in Escherichia coli DH5 alpha competent cells as FLAG fusion proteins, which were purified by anti-FLAG immunoaffinity chromatography. Of 16 selected ITP sera containing anti-GPIb/IX, 6 reacted in microtiter radioimmunoassays (RIAs) with recombinant protein fragment 2 (aas 240 to 485); 1 also with fragment 1 (aas 1 to 247). When synthetic peptides corresponding to 4 segments of fragment 2 with high antigenic indices (P1 to P4) were used as targets in RIAs, all 6 sera reacted with P2 (aas 326 to 346); 1 also reacted with P4 (aas 389 to 412). P2 was shown to be present on the surface of intact platelets by adsorption studies, and anti-P2 was detected in direct eluates of platelets from ITP patients. Glycocalicin in solution effectively competed with immobilized P2 for anti-P2; P2 in solution was a less effective competitor. Epitope scanning with a panel of synthetic 15-mer peptides localized the P2 epitope to the sequence, TKEQTTFPP. Epitope definition may offer insight into the pathophysiology of and more specific treatments for ITP.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D010446	Peptide Fragments	Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.	Peptide Fragment,Fragment, Peptide,Fragments, Peptide
D011994	Recombinant Proteins	Proteins prepared by recombinant DNA technology.	Biosynthetic Protein,Biosynthetic Proteins,DNA Recombinant Proteins,Recombinant Protein,Proteins, Biosynthetic,Proteins, Recombinant DNA,DNA Proteins, Recombinant,Protein, Biosynthetic,Protein, Recombinant,Proteins, DNA Recombinant,Proteins, Recombinant,Recombinant DNA Proteins,Recombinant Proteins, DNA
D002908	Chronic Disease	Diseases which have one or more of the following characteristics: they are permanent, leave residual disability, are caused by nonreversible pathological alteration, require special training of the patient for rehabilitation, or may be expected to require a long period of supervision, observation, or care (Dictionary of Health Services Management, 2d ed). For epidemiological studies chronic disease often includes HEART DISEASES; STROKE; CANCER; and diabetes (DIABETES MELLITUS, TYPE 2).	Chronic Condition,Chronic Illness,Chronically Ill,Chronic Conditions,Chronic Diseases,Chronic Illnesses,Condition, Chronic,Disease, Chronic,Illness, Chronic
D003001	Cloning, Molecular	The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.	Molecular Cloning
D005260	Female		Females
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000918	Antibody Specificity	The property of antibodies which enables them to react with some ANTIGENIC DETERMINANTS and not with others. Specificity is dependent on chemical composition, physical forces, and molecular structure at the binding site.	Antibody Specificities,Specificities, Antibody,Specificity, Antibody