PubMed Health⌕ Search

Biomedical subjects

V Jallu

Publications and source records attributed to V Jallu.

11 recordsLinked to original sources
PubMed2006

Predictive value of sequential maternal anti-HPA-1a antibody concentrations for the severity of fetal alloimmune thrombocytopenia.

BACKGROUND: Fetal/neonatal alloimmune thrombocytopenia results from maternal immunization against fetal platelet alloantigens (HPAs), and the major risk is intracranial hemorrhage. The severity of thrombocytopenia increases in subsequent pregnancies, and antenatal therapy has been developed. Until now, the fetal status can only be assessed by fetal blood sampling, which carries a risk of fetal loss or premature delivery. OBJECTIVES: To develop non-invasive methods to gain information on the fetal condition. PATIENTS/METHODS: Quantification of the maternal anti-HPA-1a alloantibody concentration was performed with a standardized monoclonal antibody-specific immobilization of platelet antigens (MAIPA) procedure for 43 mothers. A correlation between this concentration and the fetal/neonatal platelet counts was studied. RESULTS: (i) Before antenatal therapy, there was a significant correlation between maternal anti-HPA-1a concentrations > or =250 AU mL(-1) and fetal thrombocytopenia (2-66 x 10(9) L(-1)) whatever the gestational age (Fisher's exact test P = 0.0021). (ii) During subsequent pregnancies, we observed a decrease of the maternal anti-HPA-1a concentration for 14/19 women. Just before delivery, all women had anti-HPA-1a concentrations <250 AU mL(-1). In four cases, there was a therapy failure and the severely thrombocytopenic babies required postnatal therapy. CONCLUSION: The maternal anti-HPA-1a concentration could provide obstetricians with clinically useful information concerning the appropriateness and the timing of invasive monitoring procedures. However, though we observed a tendency toward a decrease in maternal antibody concentration after treatment, this finding does not allow us to draw any conclusions on the effectiveness of therapy.

Antigens, Human Platelet↗
PubMed1998

Human platelet antigen genotyping using a fluorescent SSCP technique with an automatic sequencer.

The typing of human platelet antigens (HPA) can be useful in many clinical situations such as neonatal alloimmune thrombocytopenia, post-transfusion purpura, and platelet transfusion refractoriness. The fluorescent-based single-strand conformation polymorphism (F-SSCP) technique is a fast and convenient way to perform HPA genotyping. Universal sequences from phage M13 were introduced at both ends of specific PCR-products by using 5'-tailed primers. A short second round of PCR with universal primers coupled to Cy-5 enabled the PCR-products to be fluorescently labelled. F-SSCP was performed by gel electrophoresis on an automated fluorescent DNA analyser. Genotyping of the three major HPA systems carried by the GP IIb-IIIa complex showed the F-SSCP technique to be accurate and reliable. A single gel procedure has been sufficient to detect HPA genetic polymorphisms tested to date. Neither restriction enzyme, radioactive material, nor any other hazardous chemicals such as ethidium bromide were required. This technique enabled us to genotype HPA-1, -3 and -4 alleles easily and to diagnose materno-fetal incompatibility in a rare alloantigenic system. F-SSCP is a promising technique for the detection of new mutations and/or DNA polymorphisms on a large scale.

Adult↗
PubMed1997

A three amino acid deletion in glycoprotein IIIa is responsible for type I Glanzmann's thrombasthenia: importance of residues Ile325Pro326Gly327 for beta3 integrin subunit association.

Glanzmann's thrombasthenia (GT) is a recessive autosomal bleeding disorder characterized by abnormal platelet aggregation due to a qualitative or quantitative defect of the glycoprotein (GP) IIb-IIIa complex (integrin alphaIIb beta3). We describe a new mutation in the GPIIIa gene responsible for type I GT in a consanguineous Algerian family. A discordance between phenotyping and genotyping of the GPIIIa-related HPA-1 platelet alloantigen system in three family members heterozygous for the disease suggested a genetic defect in the GPIIIa gene and a normal GPIIb gene. Sequence analysis of amplified genomic DNA fragments showed a 6-bp deletion in exon 7 of the GPIIIa gene resulting in the amino acid deletion/substitution (Ile325pro326Gly327 --> Met) and creating a new BspHI restriction site. Expression of the mutated integrin beta3 subunit cDNA in Chinese hamster ovary cells showed that the cDNA gene was transcribed into a full-length beta3 protein with an apparent molecular weight identical to wild-type beta3 and accumulated as a single-chain molecule in the cell cytoplasm. The absence of heterodimeric complex formation of the mutant beta3 protein with endogenous alpha v was shown by immunoprecipitation experiments, intracellular immunofluorescent labeling, and a semiquantitative enzyme-linked immunosorbent assay using the alpha vbeta3 complex-specific monoclonal antibodies LM609 and 23C6. Substitution of the methionine residue by a proline, present at position 326 of wild-type beta3, did not restore the ability of the recombinant mutant beta3 protein to associate with alpha v , suggesting that the Ile-Pro-Gly motif is located in a beta3 domain important for integrin subunit interaction. The association of a BspHI restriction site with this newly identified mutation has allowed allele-specific restriction analysis of Algerian GT individuals and the identification of two new unrelated type I patients exhibiting the same mutation, suggesting that the described mutation might be significant in this population and that BspHI restriction analysis will provide a useful screening assay for antenatal diagnosis and genetic counselling.

Algeria↗
PubMed1994

Two human antibodies reacting with different epitopes on integrin beta 3 of platelets and endothelial cells.

Glanzmann's thrombasthenia is an inherited bleeding disorder that results from a deficit of glycoprotein (GP) IIb-IIIa complexes in platelets. Patient (EBV) is an adult male with GP IIb-IIIa levels < 5% of normal values and a history of blood transfusions. Western-blot analysis revealed a strong IgG antibody to GP IIIa in his plasma. The determinants were localized to the minimum-sized fragment of GP IIIa (50 kDa) retained on chymotrypsin-treated platelets and were lost on reduction of disulphides. A female patient (AF), previously described by us [Jallu, V., Pico, M., Chevaleyre, J., Vezon, G., Kunicki, T.J. & Nurden, A.T. (1992) Hum. Antibod. Hybridomas 3, 93-106] developed her anti-GP-IIIa antibody during pregnancy. This antibody was poorly reactive with the 50-kDa proteolytic fragment, yet bound to 115-kDa and 60-kDa hydrolytic products of GP IIIa. Antibodies from both patients recognized the GP-IIIa-like protein of endothelial cells, thus confirming that they were directed against the integrin beta 3-subunit. The (EBV) antibody reacted strongly with GP IIb-IIIa in an antigen capture assay performed with each of a panel of four murine monoclonal antibodies (mAbs) recognizing different epitopes on GP IIb-IIIa. In contrast, that from (AF) was specifically inhibited by AP-3, a murine mAb whose epitope is thought to be localized between amino acids 324-422 of GP IIIa. The residual GP IIb and GP IIIa contents of platelets from each patient were assessed in Western blotting using chemiluminescence detection. SZ-22, a murine mAb to the GP IIb heavy chain (140 kDa), located small amounts of a 130-kDa protein in (EBV) platelets. The anti-GP IIIa mAbs XII F9, P 37 and P 97 revealed trace amounts of protein with a relative mobility identical to that of GP IIIa in both (AF) and (EBV) platelets. This residual GP IIIa represented less than 0.5% of the amount in normal platelets. When, for each patient, plasma was tested in Western blotting against their own platelets, autoantibody activity to the residual GP IIIa was detected in both cases. Thus, patients (AF) and (EBV) have developed anti-GP-IIIa antibodies with restricted and distinct epitopes but recognizing self antigens.

Antigen-Antibody Reactions↗
PubMed1992

Further evidence that heparin-dependent thrombocytopenia may result from Fc receptor-mediated interactions.

Heparin-dependent thrombocytopenia (HDT) and associated thrombotic complications, are thought to be linked to the appearance of anti-platelet antibodies. Attempts were made to characterize the antibodies in the sera from 10 such patients. Western blotting against platelet antigens was inconclusive, often revealing multiple bands but with considerable variability from patient to patient. An often seen band of approximately 83 kDa was also given by some nonimmune sera and the antigen appeared to be predominantly intracellular in origin. Antibodies to major membrane glycoproteins were not readily apparent. This was confirmed by the MAIPA ("Monoclonal Antibody Immobilization of Platelet Antigens") test, performed to detect antibodies to GP Ib-IX and GP IIb-IIIa. Only one weak activity to GP Ib-IX and one weak activity to GP IIb-IIIa were detected. In contrast, an antibody to the PlA1 alloantigen was readily detected in the serum of an additional patient. The ability of HDT serum to induce the aggregation of control platelets was studied in detail. Aggregation was inhibited by EDU-3, a monoclonal antibody to GP IIb-IIIa complexes, and by the synthetic peptide RGDS, suggesting an involvement of the same pathway as used by physiologic agonists. However, in agreement with Chong et al (Thromb Res 55:291, 1989), we observed that aggregation was inhibited by rabbit IgG, suggesting that it was Fc-receptor mediated. Interestingly, 2E1, a monoclonal antibody to the Fc gamma RII receptor, induced platelet aggregation with a lag phase, a characteristic of HD antibodies. Nonetheless, for different donors, there was no correlation between the length of the lag phase induced by 2E1 and HD antibodies. Fc-receptor blockade should be considered as a means for diminishing the clinical complications of HDT.

Adult↗
PubMed1992

Characterization of an antibody to the integrin beta 3 subunit (GP IIIa) from a patient with neonatal thrombocytopenia and an inherited deficiency of GP IIb-IIIa complexes in platelets (Glanzmann's thrombasthenia).

Patient A.F. is a 28-year-old polytransfused woman with an inherited bleeding disorder, Glanzmann's thrombasthenia. An abnormal platelet function is linked to severe decreases in the platelet content of the integrins GP IIb and GP IIIa. In 1987 the patient gave birth to a child with severe anemia and thrombocytopenia. Serological tests revealed the presence of anti-platelet antibody together with an anti-Rhesus D. Western blotting identified a major antibody that reacted with a protein of 90-95 kDa present in platelets and endothelial cells. This was identified as the beta 3 integrin subunit (GP IIIa). Antibody-binding required intact disulfides, while controlled digestion with proteases showed the determinant(s) to be retained within chymotrypsin- (50, 63 kDa) and Staphylococcus aureus V8 protease-derived (25-38 kDa) fragments of GP IIIa. Direct binding assays performed in the presence of monoclonal antibodies specific for different epitopes on GP IIb-IIIa complexes confirmed that the epitope was exposed on intact platelets and revealed a specific inhibition of A.F. IgG binding by the monoclonal antibody, AP-3. Other tests confirmed that the antibody reacted independently of the PlA or Pen polymorphisms carried by GP IIIa. IgG purified from A.F. plasma by adsorption and elution from paraformaldehyde-fixed normal platelets or electrophoretically separated GP IIIa was an inhibitor of ADP-induced platelet aggregation. Unexpectedly, Western blotting showed trace amounts of abnormally migrating GP IIIa in A.F. platelets, which retained an ability to react with her antibody. This suggests that the patient has formed an autoantibody reactive with an active site of the beta 3 integrin subunit and linked to the development of neonatal thrombocytopenia.

Adult↗