PubMed Health⌕ Search

Biomedical subjects

C Proulx

Publications and source records attributed to C Proulx.

17 recordsLinked to original sources
PubMed1997

Human monoclonal Fab fragments recovered from a combinatorial library bind specifically to the platelet HPA-1a alloantigen on glycoprotein IIb-IIIa.

BACKGROUND AND OBJECTIVES: Certain clinical conditions are related to the presence of platelet-specific alloantibodies in the patient's serum. We studied the molecular diversity of HPA-1a antibodies to analyze some peculiarities of this antibody response. MATERIALS AND METHODS: Human antibody Fab fragments that bind to the platelet alloantigen HPA-1a on glycoprotein IIb-IIIa (GPIIbIIIa) were generated by using a recombinant phage display system. We established an immunoglobulin G1, kappa combinatorial library from the peripheral blood lymphocytes of a person undergoing a severe posttransfusion purpura. RESULTS: Characterization of Fab clones selected from the fifth round of antigen-specific panning of this library demonstrates a highly specific reactivity to the HPA-1a alloantigen. The nucleotide sequence analysis of representative HPA-la-specific clones reveals at least 3 distinct V1 and 3VH gene segments that present an extensive degree of mutation as demonstrated by comparison of gene usage and homologies to the nearest germline genes. CONCLUSIONS: These human HPA-la-specific Fab reagents should allow us to better understand the molecular mechanism involved in HPA-la alloimmunization.

Amino Acid Sequence↗
PubMed1996

Presence in peripheral blood of healthy individuals of autoreactive T cells to a membrane antigen present on bone marrow-derived cells.

Intrathymic clonal deletion is thought to be the major mechanism responsible for tolerance to nonsequestered antigens such as the ones expressed by bone marrow-derived cells. In the case of sequestered antigens that potentially do not come in contact with T cells in the thymus, it is thought that autoreactive T cells are present in periphery but are tightly regulated to prevent autoimmune disease. Indeed, autoreactive T cells to sequestered antigens can be isolated in healthy individuals. However, the presence of autoreactive T cells to nonsequestered circulating antigens had not been observed. In this report, we present evidence for the presence, in the periphery of all healthy individuals tested (n = 25), of autoreactive T cells to GpIIb-IIIa, a membrane antigen present on bone marrow-derived cells that is expressed on circulating platelets and on the cell surface of the epithelial cells of the thymic stroma early in intrauterine life. Using an in vitro T-cell proliferation assay, we have demonstrated that activation of these specific GpIIb-IIIa autoreactive alpha beta TCR+ CD4+ CD8- T cells requires internalization and processing of the GpIIb-IIIa by antigen-presenting cells and its presentation by HLA-DR class II molecules in the presence of exogenous interleukin 2 (IL-2). This indicates that some autoreactive T cells directed against membrane antigens present on bone marrow-derived cells and also expressed in the thymus are not necessarily eliminated by intrathymic deletion.

Antigen-Presenting Cells↗
PubMed1994

Analysis of immunoglobulin class, IgG subclass and titre of HPA-1a antibodies in alloimmunized mothers giving birth to babies with or without neonatal alloimmune thrombocytopenia.

We analysed the titre and isotype composition of antibodies produced by mothers giving birth to babies with or without neonatal alloimmune thrombocytopenic purpura (NAITP) and patients with post-transfusion purpura (PTP). All these individuals produced an antibody specific for the HPA-1a allotype present on the platelet glycoprotein IIb-IIIa (GPIIb-IIIa). Sera from mothers who gave birth to thrombocytopenic babies (group 1, n = 36), non-thrombocytopenic babies (group 2, n = 4) or from PTP patients (group 3, n = 3) were tested by an indirect-ELISA. Results indicated no evident differences in the isotype composition or titre of the antibodies from the three groups of sera. The antibody titre ranged from 1:120 to 1:3500. Antibodies with the IgG1 subclass were present in all sera. Most sera contained IgG1 alone (24/43 sera tested) or in combination with IgG3 (10/43). IgG2 was never present and only three sera showed intermediate reactivity with anti-IgG4 MAb. Few sera (nine sera from groups 1 and 2) were weakly positive when tested with the anti-IgM antibodies. These results suggest that neither the titre nor the isotype composition can be used to predict the severity or the occurrence of thrombocytopenia in newborns.

Adult↗
PubMed1992

Epitope analysis of an immunodominant domain on the P1 protein of Haemophilus influenzae type b using synthetic peptides and anti-idiotypic antibodies.

Synthetic peptides, anti-idiotypic antibodies (anti-Id) and human and murine monoclonal antibodies (mAbs) were used to further define a major antigenic domain on the outer membrane P1 protein (OMP) of Haemophilus influenzae type b (Hib). Synthetic peptides were elaborated from the known primary sequences of the P1 protein of prototype Hib strains MinnA (OMP subtype 1H) and 8358 (OMP subtype 6U). By peptide mapping, antibodies are categorized into three groups: A, B and C. A first epitope on the P1 from strain MinnA was identified by the reactivity of one set of murine anti-P1 mAbs with the two overlapping peptides 11H and 13H, corresponding to amino acid residues 384-412 and 400-437, respectively. On the basis of their reactivity with both peptides, these mAbs were designated as group A. Anti-Id obtained from mice immunized with two group A mAbs reacted specifically with all group A mAbs. A second epitope on the same P1 protein was identified by the reactivity of the peptide 13H with another distinct set of murine anti-P1 mAbs assigned to group B. This group of mAbs did not recognize the peptide 11H. Murine anti-Id which were prepared against one group B mAb inhibited the attachment of this mAb to outer membrane preparations, whereas the binding of the other group B mAbs was not affected, suggesting that these mAbs represent a heterologous group of mAbs. The epitope(s) recognized by two human anti-P1 mAbs was (were) distinct from the ones recognized by murine mAbs since no reactivity with the peptides was observed. Similarly, the binding of the two human mAbs to the P1 antigen was not inhibited by anti-Id raised against group A or B mAbs. Interestingly, an epitope on a different P1 protein recovered from strain 8358 was identified by the reactivity of group C murine mAbs with the peptide 13U, which occupies the same position on the P1 protein as 13H but differs from the latter by 10 amino acid residues. Our studies demonstrated the presence of several distinct surface-exposed B-cell epitopes within the antigenic domain which was defined previously on the P1 protein of Hib MinnA. Furthermore, we showed the immunodominance of this region on two different P1 proteins. None of the mAbs, however, had a bacteriolytic or protective activity against Hib strains. We suggest that the surface-exposed immunodominant region on the OMP P1 of Hib do not induce protective antibodies against Hib infection.

Amino Acid Sequence↗
PubMed1992

Outer membrane proteins P1 and P2 of Haemophilus influenzae type b: structure and identification of surface-exposed epitopes.

The outer membrane proteins (OMPs) P1 and P2 of Haemophilus influenzae type b exhibit molecular size and antigenic variation. Their structural genes have been cloned from prototype isolates of the most common disease-producing clonal groups. The derived amino acid sequences of P1 from strains of OMP subtypes 1H, 3L, and 6U have three variable regions between highly conserved regions. An immunodominant surface-exposed epitope was identified near the carboxyl terminus of P1 proteins from subtype 1H and 3L strains. The P2 genes from subtype 1H, 1L, and 3L isolates were identical. The P2 gene sequence from a subtype 6U isolate differs from the subtype 1H P2 gene by 13 nucleotides, resulting in 10 amino acid changes. The P2 gene from a subtype 2L isolate differs by 1 nucleotide from the subtype 1H P2 gene, resulting in 1 amino acid change at position 166. Two surface-exposed epitopes of OMP P2 were identified, one each between residues 158 and 174 and residues 319 and 341.

Animals↗
PubMed1992

Localization of conserved B-cell epitopes among encapsulated and non-encapsulated Haemophilus influenzae P2 porin proteins using synthetic peptides.

The P2 outer membrane protein of Haemophilus influenzae belongs to a class of apparently ubiquitous proteins in Gram-negative bacteria that function as porins. Murine hybridomas raised to the P2 protein and synthetic peptides were used to investigate the structural and antigenic relationships among P2 proteins of encapsulated and non-encapsulated H. influenzae. Three monoclonal antibodies (mAbs), P2-17, P2-18 and P2-19, recognizing epitopes on the P2 protein, as shown by Western immunoblotting of outer membrane preparations, and purified and recombinant P2 proteins are described. The epitopes reactive with the mAbs were widely distributed among H. influenzae strains since 70-100% of strains of encapsulated and non-encapsulated isolates collected worldwide were recognized by individual mAbs. None of the mAbs reacted with H. parainfluenzae or other bacterial species. The peptide composition of P2 epitopes was determined by analysis of mAb reactivity with a series of overlapping synthetic peptides that covered the amino acid sequences of H. influenzae type b. The domains recognized by these mAbs were completely distinct. mAb P2-18, reactive with an epitope conserved among all H. influenzae P2 porin molecules which were screened, recognized a peptide corresponding to the N-terminal segment (residues 1-14). The P2-17- and P2-19-specific epitopes were located between residues 28 and 55, and 101 and 129, respectively. None of the epitopes were exposed on the cell surface since no mAbs bound to intact live bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Identification of a surface-exposed immunodominant epitope on outer membrane protein P1 of Haemophilus influenzae type b.

Eight murine monoclonal antibodies (MAbs) directed against outer membrane protein P1 of Haemophilus influenzae type b were generated and characterized. Seven of the eight MAbs reacted with recombinant P1 and purified P1 protein from H. influenzae type b strains MinnA and 1613; MAb P1.8 was specific for the latter strain. A panel of 32 nontypeable and 140 encapsulated Haemophilus strains recovered worldwide representing the major clonal families of serotypes a, b, and d was used to evaluate the distribution among Haemophilus strains of the epitopes identified by the P1-specific MAbs. The epitope reactive with the seven MAbs which recognized P1 from strains MinnA and 1613 was shared by 92% of the encapsulated Haemophilus isolates tested. The epitope is present in the H. influenzae type b strains from clonal families commonly recovered from cases of invasive disease in North America and Europe. A series of nested 5' and 3' deletions of the P1 gene were constructed and analyzed to localize the determinants on P1 recognized by the MAbs. MAbs P1.2, P1.4, P1.5, P1.6, and P1.7 recognized an epitope localized to the carboxy-terminal portion of P1. Murine MAbs P1.1 and P1.3 and two human MAbs, HiH-7 and HiH-10, recognized a complex epitope which was partially localized to the carboxy-terminal portion of the P1 protein. These data indicate that an immunodominant surface-exposed epitope is present on the carboxy-terminal portion of the P1 protein of type b Haemophilus isolates responsible for the majority of invasive disease in North America.

Amino Acid Sequence↗
PubMed1989

Importance of lymphokines in the control of multiplication and dispersion of Leishmania donovani within liver macrophages of resistant and susceptible mice.

Leishmania donovani is an obligate intracellular parasite of mammalian macrophages. The immunosuppressant cyclosporin A (CsA), which inhibits the production of interleukin (IL)-1, IL-2, and interferon-gamma, increased infections 3-fold without affecting expression of the Lsh gene. The objective of this study was to determine how activation of macrophages by lymphokines affects the multiplication and propagation of the parasite within liver macrophages. Susceptible C57BL/6J and resistant C57L/J mice were treated with 200 mg/kg CsA and then infected intravenously with 10(7) amastigotes. Two weeks later macrophages were collected from the liver by perfusion, plated on coverslips, and incubated for 4, 24, and 48 hr. The percentage of infected macrophages and the number of amastigotes/100 cells were determined after staining the cells with Giemsa's stain. The number of infected macrophages and amastigotes per macrophage was significantly greater in animals of both strains that had been treated with CsA. This study demonstrated clearly that lymphokines or other soluble mediators produced by T cells act, in part, to control infection by L. donovani by minimizing both multiplication within macrophages and their dispersion.

Animals↗
PubMed1989

Infectivity and route of penetration in rats after oral and intraperitoneal inoculations of bloodstream and in vitro-cultured metacyclic forms of Trypanosoma lewisi.

Morphological changes of Trypanosoma lewisi blood trypomastigotes cultured in Schneider's Drosophila medium (SDM), supplemented or not with uric acid (SDM + UA), were compared to those that occurred in a control medium (M-199). No difference in trypanosome morphology and numbers was observed between SDM + UA and SDM cultures; there was little transformation into metacyclic stages in M-199. No difference was observed between the capacity of SDM- or SDM + UA-cultured metacyclic stages to infect rats. The infectivity of bloodstream forms was always higher than that of the SDM- or SDM + UA-cultured forms, whether inoculated orally or intraperitoneally. The oral inoculation of rats with tritium-labeled culture and bloodstream forms showed that the metatrypanosomes from the cultures remained longer in the salivary glands and tongue of the animal than the blood trypanosomes.

Animals↗
PubMed1982

[Parosteal osteogenic sarcoma: a study of four cases].

The authors present four cases of parosteal osteogenic sarcoma, which is a rare primary tumour of bone. The radiologic and histopathologic features are discussed. The discussion concerns mostly the indication for "en bloc resection" as the initial treatment with or without replacement by autogenous or homogenous bone graft. Amputation should be considered when there is local recurrence.

Adolescent↗