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V Quaranta

Publications and source records attributed to V Quaranta.

At least 91 records · Page 5Linked to original sources
PubMed1987

The HLA-class II-associated chondroitin sulfate proteoglycan expressed by class II positive T and monocyte-like cell lines is larger than that expressed by EBV-transformed B-lymphoblastoid cell lines.

The human class II-associated chondroitin sulfate proteoglycan (CSPG) was originally detected as an approximately 40-70 kd species from normal human tonsil cells and Epstein-Barr virus (EBV) transformed B-lymphoblastoid cell lines. The identification of the invariant chain as the core protein of the CSPG allowed us to directly assay for the CSPG on both class II positive and negative immunocompetent cells of other lineages. Our results indicate that the CSPG is present on the class II-positive monocyte-like cell line U937 and T-cell line HUT-102, but not on the class-II negative T-cell line CCRF/CEM. No class II positive cells were found that did not also express the CSPG. The expression of the CSPG on U937 cells is increased after stimulation with gamma-interferon and PMA, paralleling the previously described increase in class II and invariant chain expression. In addition, the CSPGs from U937, HUT-102, and Raji, all cell lines derived from human malignancies, migrate as an approximately 55-90 kd species, larger than the CSPG previously characterized. However, the core proteins of the CSPG from all cells studied appear as two bands of 38 and 28 kd, indicating the size difference in the CSPG is attributable to differences in the glycosaminoglycan chains.

B-Lymphocytes↗
PubMed1987

Binding of monoclonal antibody (4F2) to its cell surface antigen on dispersed adenomatous parathyroid cells raises cytosolic calcium and inhibits parathyroid hormone secretion.

In the course of characterizing monoclonal antibodies (MAbs) recognizing cell surface antigens on dispersed human parathyroid cells (dPTCs), we identified one MAb (4F2) that bound avidly to parathyroid cells and had marked effects on parathyroid function. The binding of MAb 4F2 to human adenomatous dPTCs resulted in a marked [53.8 +/- 7.9% (+/- SEM)] reduction in low calcium (Ca)-stimulated PTH secretion to levels equivalent to those in cell suppressed by high extracellular Ca (1.5 mM). Typically, these functional effects were optimal at antibody dilutions of 1:10(4) to 1:10(5). Cell viability was confirmed at the conclusion of each experiment by trypan blue exclusion (greater than 90-95%) and cell surface immunofluorescence. Parallel studies using the Ca-sensitive dye Quin-2 showed that inhibition of PTH secretion in 4F2-treated cells was associated with a concomitant increase in cytosolic Ca (Cai) of 188% in 0.5 mM Ca; these values also approached Cai levels in control cells incubated in high Ca. Mab controls, P3 X 63, which do not bind to dPTCs, and Mab LC7-2, which recognizes a different epitope of the same antigen as 4F2 on dPTCs, did not alter PTH secretion or Cai. Immunoprecipitation of 125I-labeled parathyroid cell extracts with MAb 4F2 demonstrated proteins with mol wt of approximately 145, 85, and 45 under nonreducing conditions and 85 and 45 kilodaltons after reduction with 5% mercaptoethanol. These studies suggest that 1) Mab-4F2 binding to its cell surface antigen inhibits PTH secretion by human adenomatous parathyroid cells in vitro; 2) the alterations in secretory function could be related to by an attendant increase in Cai; 3) the 4F2 antigen on dPTCs is a heterodimeric protein of (approximately) 85K and 45K; and 4) the 4F2 antigen may be an important component of the Ca-sensing and/or signal-transducing mechanism in this cell.

Adenoma↗
PubMed1986

The human invariant chain is the core protein of the human class II-associated proteoglycan.

The human class II-associated chondroitin sulfate proteoglycan (CSPG) was analyzed biochemically and immunologically to determine a possible relationship with the human invariant chain (gamma 1) and its related components. The CSPG was purified by a three-step procedure involving associative ion-exchange chromatography, immunoprecipitation, and dissociative ion-exchange chromatography. Treatment of the CSPG with chondroitinase revealed core proteins of Mr approximately 46,000, 38,000, and 28,000, with the 38,000 species most highly represented. Tryptic peptide analysis revealed identity of the peptides of the 38,000 Mr core protein and gamma 1, and of the 28,000 Mr species and p25. The CSPG and its core proteins were shown to react directly with the mouse anti-human invariant chain monoclonal antibody VIC-Y1 and a rabbit antiserum produced against a synthetic peptide corresponding to the C-terminal end of invariant chain. These results demonstrate that the invariant chain is the core protein of the class II-associated CSPG. In addition, virtually all the CSPG was shown to be present on the cell surface.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1986

Ammonium chloride interferes with a distinct step in the biosynthesis and cell surface expression of human melanoma-type chondroitin sulfate proteoglycan.

Human melanoma cells synthesize a cell-associated chondroitin sulfate-rich proteoglycan, whose core protein is recognized by monoclonal antibody 9.2.27. We report that the core protein is present on the surface of melanoma cells in two forms, either free or modified by the addition of chondroitin sulfate chains, suggesting that the addition of glycosaminoglycan chains may not be a prerequisite for cell surface expression of the proteoglycan core protein. Free core protein found at the cell surface does not seem to represent an overflow of the proteoglycan synthetic pathway, since experiments using a beta-D-xyloside acceptor suggest that core protein is, in fact, limiting proteoglycan synthesis. NH4Cl inhibits the synthesis of melanoma-type proteoglycan, shifting the balance of surface core protein toward the free form. The inhibition of proteoglycan synthesis is apparently not due to a disruption of enzymes and precursors involved in glycosaminoglycan synthesis, since cells treated with NH4Cl retain their ability to initiate and elongate chondroitin 4-sulfate chains on a beta-D-xyloside acceptor. In contrast, the divalent ionophore monensin inhibited core protein maturation and synthesis of glycosaminoglycan chains. The effects of both NH4Cl and monensin were reversible; thus, experiments using the drugs sequentially indicated that monensin temporally precedes NH4Cl in interfering with proteoglycan biosynthesis. Since the NH4Cl and monensin share the property of inhibiting the acidification of intracellular vesicles within cells, the present findings raise the possibility that the accessibility of proteoglycan core protein to the Golgi site of glycosaminoglycan addition is regulated in melanoma cells by acidification of intracellular compartments.

Aggrecans↗
PubMed1986

Structure of the human Ia-associated invariant (gamma)-chain gene: identification of 5' sequences shared with major histocompatibility complex class II genes.

The human gene encoding the Ia-associated gamma (or invariant) chain was isolated by screening a genomic library in phage lambda with cDNA probes. The frequency of positive clones in the library, the overlapping restriction maps of the cloned fragments, and the patterns of genomic hybridization suggested that the gamma-chain gene exists as a single copy per haploid genome. The gene consists of 8 exons, spanning approximately 12 kilobases of DNA. All exon sequences were in an open reading frame, contained appropriate splice junction sequences, and encompassed the entire sequence of full-length gamma-chain mRNA, suggesting that the gene we isolated is most likely functional. Furthermore, "CAAT"-type and "TATA"-type promoter sequences were found at the expected positions upstream from the proposed cap site. The organization of the gamma-chain gene has none of the distinctive features of the immunoglobulin superfamily of genes, of which Ia alpha and beta chains are members. Therefore, the evolutionary origins, and perhaps the functions, of the Ia gamma chains are distinct from those of the other two Ia subunits alpha and beta. Despite the unrelatedness of these genes, consensus sequences found approximately 150 base pairs upstream from all the Ia alpha- and beta-chain genes sequenced to date were also found in analogous positions in the gamma-chain gene, suggesting a possible role in the coregulation of expression of these genes.

Base Sequence↗
PubMed1985

Chloroquine affects biosynthesis of Ia molecules by inhibiting dissociation of invariant (gamma) chains from alpha-beta dimers in B cells.

Biosynthetic conversion of Ia oligomers from three chains (alpha, beta, gamma) to two (alpha, beta) before surface expression was inhibited in B lymphoid cells by treatment with chloroquine, resulting in the accumulation of Ia complexes composed of mature alpha and beta chains, and gamma chains at various states of sialylation. Other stages of Ia biosynthesis and processing appeared unaffected, indicating that chloroquine selectively interfered with the gamma chain dissociating mechanism itself. Similar effects were also observed with ammonium chloride. Because of the nature of such lysosomotropic agents, these results suggest that an intracellular acidic compartment may be involved in processing Ia oligomers to accomplish dissociation from gamma chains. Since chloroquine is known to inhibit Ia-restricted antigen presentation in accessory cells, our results raise the possibility that the pathways of antigen processing and Ia biosynthesis may use some common intracellular compartments.

B-Lymphocytes↗
PubMed1985

Neuritic plaques and cerebrovascular amyloid in Alzheimer disease are antigenically related.

A synthetic peptide (Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr), homologous to the amino terminus of a protein purified from cerebrovascular amyloid (beta protein), induced antibodies in BALB/c mice that were used immunohistochemically to stain not only amyloid-laden cerebral vessels but neuritic plaques as well. These findings suggest that the amyloid in neuritic plaques shares antigenic determinants with beta protein of cerebral vessels. Since the amino acid compositions of plaque amyloid and cerebrovascular amyloid are similar, it is likely that plaque amyloid also consists of beta protein. This possibility suggests a model for the pathogenesis of Alzheimer disease involving beta protein.

Alzheimer Disease↗
PubMed1984

A human Ia cytoplasmic determinant located on multiple forms of invariant chain (gamma, gamma 2, gamma 3).

An antigenic determinant present in the cytoplasm, but not on the surface membrane of human Ia+ cells, is defined by a monoclonal antibody (VIC-Y1) and is shown by immunoprecipitation and by NEPHGE to be expressed by Ia oligomers. Immunoprecipitations of cellfree translates and of purified Ia subunits indicate that the VIC-Y1 determinant is located on the Ia gamma-(invariant) chain, as well as on two other related molecules, provisionally termed gamma 2 and gamma 3. Within our experimental conditions, the three forms of gamma-chains co-precipitate exclusively with Ia oligomers. As detected by VIC-Y1 and in the limits of our assays, gamma-chains could not be found at the cell surface; their tissue distribution, determined by cytoplasmic indirect immunofluorescence with VIC-Y1, closely resembles that of Ia antigens, with the possible exception of acute lymphatic leukemia cells (Ia+, gamma-chain-).

Animals↗
PubMed1982

A recurrent idiotype on monoclonal anti-human Ia antibodies.

We report a recurrent idiotype on a remarkably high fraction (4/19) of murine monoclonal antibodies specific for human Ia monomorphic determinants and elicited by separate immunizations. For three of them, the shared idiotype is associated with the antigen-combining site. These results indicate that the spectrum of mouse antibody responses to human Ia antigens may be based on recurrent idiotypes, suggesting a limited potential repertoire of murine monoclonal antibodies to human Ia antigens. Anti-idiotypic reagents might be helpful in dissecting this repertoire and to generate a mirror image of a human Ia antigenic map. Furthermore, antisera to the idiotype of antibodies specific for human Ia monomorphic determinants might help in elucidating the interactions between Ia molecules and receptors on immune cells.

Animals↗
PubMed1981

The free and the beta 2-microglobulin-associated heavy chains of HLA-A, B alloantigens share the antigenic determinant recognized by the monoclonal antibody Q1/28.

Serological and immunochemical assays have shown that the monoclonal antibody Q1/28 recognizes an antigenic determinant which is expressed on the heavy chain of subsets of HLA-A, B antigens and is distinct from those defining the serological polymorphism of this system. Association of the HLA-A, B heavy chain with beta 2-microglobulin is not required for expression of the antigenic determinant recognized by the monoclonal antibody Q1/28, since this antibody can immunoprecipitate a 45 000 m.w. component from radiolabeled lymphoid-cell glycoproteins immunodepleted with either an anti-human beta 2-microglobulin xenoantiserum or the MoAb W6/32 to framework determinants of HLA-A, B, C antigens. Furthermore, the MoAb Q1/28 can immunoprecipitate a 45 000 m.w. component from an NP40 lysate of radiolabeled Daudi cells, which lack the genetic information for beta 2-microglobulin. The determinant recognized by the MoAb Q1/28 is relatively resistant to denaturing treatments and does not appear to be carbohydrate in nature. The MoAb Q1/28 is the first example of an antibody which recognizes an antigenic determinant expressed on both the beta 2-microglobulin-associated and free HLA-A, B heavy chains.

Antibodies, Monoclonal↗
PubMed1981

Cross-reactivity between human and murine lymphocyte antigens. IV. Reactivity of H-2 alloantisera with HLA-A, B antigens.

The anti-H-2 alloantiserum D-32 [(B10.A(2R) x C3H.SW) anti-C3H] is cytolytic to human lymphocytes. Fab2 blocking assays, indirect immunoprecipitation and sequential immunoprecipitation experiments showed that the anti-H-2 alloantiserum D-32 recognizes antigenic determinants which are expressed on the heavy chain of subpopulations of HLA-A, B antigens. These determinants are different from those defining the serological polymorphism of the HLA-A, B, C system, are the same as or spatially close to those recognized by the anti-HLA-A, B monoclonal antibody Q6/64 and are expressed on rabbit, rat or guinea pig lymphocytes.

Animals↗
PubMed1981

The monoclonal xenoantibody Q6/64 recognizes a determinant expressed by certain gene products of the A and B loci of the HLA region.

A combination of serological (cytotoxicity, binding assay, lysostrip) and immunochemical (indirect immunoprecipitation, sequential immunoprecipitation, two-dimensional gel electrophoresis) assays have shown that the monoclonal antibodies Q6/64 recognizes an antigenic determinant which is expressed by certain gene products of the A and b loci of the HLA region. The determinant identified by Q6/64 is spatially close to those which define the serological polymorphism of the HLA-A, B, C antigenic system. The results presented in this study in conjunction which those recently published by other investigators indicate that sharing of determinants among HLA-A and -B allospecificities is more frequent than originally assumed on the basis of the cross-reactivity pattern obtained with alloantisera. This conclusion is in agreement with the high degree of homology in the primary amino-acid sequence of A and B allospecificities.

Amino Acid Sequence↗
PubMed1981

Distribution of antigenic determinants recognized by three monoclonal antibodies (Q2/70, Q5/6 and Q5/13) on human Ia-like alloantigens and on their subunits.

The distribution of antigenic determinants recognized by the anti-Ia-like antigen monoclonal antibodies (MoAb) Q2/70, Q5/6 and Q5/13 on molecules coded for by the DR locus and by non-DR loci was investigated using a binding assay with 125I-labeled Ia-like antigens isolated from four B lymphoid cell lines. The determinants reacting with the MoAb Q2/70 and Q5/13 are expressed on all DR alloantigens tested and on BR4X7 specificities, while those reacting with the MoAb Q5/6 are not detectable on DRw7 and BR4X7 molecules. None of the monoclonal antibodies reacted with DC1 molecules. The MoAb Q5/6 and Q5/13 reacted with the isolated beta subunit of the Ia-like antigenic complex, while the MoAb Q2/70 did not react with the isolated chains.

Animals↗
PubMed1981

Stimulation of human T lymphocytes by PHA-activated autologous T lymphocytes: analysis of the role of Ia-like antigens with monoclonal antibodies.

Human T lymphocytes activated with PHA express Ia-like antigens and acquire the ability to stimulate autologous T lymphocytes in mixed lymphocyte reaction. This reaction is immunological in nature since it has specificity and memory. Ia-like antigens play a role in the stimulation of T lymphocytes by autologous PHA-T lymphocytes since monoclonal antibodies to Ia-like antigens can significantly, although not completely, inhibit the stimulation.

Antibodies↗