Human Ia molecules carrying DC1 determinants differ in both alpha- and beta-subunits from Ia molecules carrying DR determinants.
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Antibodies↗
Biomedical subjects
G Corte
Publications and source records attributed to G Corte.
Surface antigens specifically expressed by activated T cells in humans.
By immunizing BALB/c mice with human T cells derived from a secondary mixed lymphocyte reaction (MLR) and successive fusion of the spleen cells with P3X63Ag8U1 myeloma cells, several monoclonal antibodies to activated T cells were obtained. Four of them (MLR 1-4) were shown to be specific for activated T cells only, showing no reactivity with peripheral blood cells. The antigens recognized by these antibodies are differently distributed and appear on T cells at different times after stimulation. Thus, MLR2 stains nearly all the responder T cells present in a secondary MLR, while MLR 1, 3 and 4 stain only a fraction. MLR2 and 3 are also present on mitogen-stimulated cells. At least 3 of these MLR antigens may define different sets of activated T cells, and are likely to become useful in monitoring T cell activation also in the course of diseases involving the immune system.
Animals↗
Binding of one monoclonal antibody to human Ia molecules can be enhanced by a second monoclonal antibody.
A monoclonal anti-human Ia antibody, PTF 29, was tested for its ability to bind purified, 125I-labeled human Ia preparations. It was found that the binding level increases considerably in the presence of a second monoclonal antibody. Experimental conditions were selected under which only the binding of PTF 29 and not the binding of the second antibody could be determined. Under these conditions, it was found that "helped" PTF 29 binding has higher affinity and is exerted on a molecular subset different from that bound by PTF 29 alone. This phenomenon, while not easily accommodated in the present conceptual framework of the human Ia system, appears in itself interesting and may have more general implications.
Animals↗
Analysis of HLA-DR polymorphism by two-dimensional peptide mapping.
Two-dimensional peptide mapping was used to study the polymorphism of DR antigens, membrane glycoproteins composed of two chains, alpha and beta, and encoded by the human major histocompatibility complex (MHC). Four DR antigens were purified by immunoabsorption from four human lymphoblastoid cell lines homozygous at the DR locus. After labeling with 125I, alpha and beta chains were separated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate and digested with pepsin. Comparison of the peptide maps showed a marked degree of polymorphism among beta chains: only 43% of peptides were common to all four chains and 15-21% of the spots were unique to a given chain. By contrast, only a limited variability was observed among alpha chains. Homology was 75% for the four chains and the percentage of unique peptides was very low. DR7 did not possess even a single unique peptide. The limited variability among alpha chains and the lack of "private" peptides in one of them point to the conclusion that the beta chain is the unique carrier of the alloantigenic specificities. Higher homology within the known crossreactive groups was not observed, suggesting that the determinants responsible for crossreactivity are on different molecules. From a genetic point of view, because beta chains show allele-associated polymorphism, they are likely to be MHC encoded, whereas the minor differences among alpha chains do not allow a similar conclusion. The available data point to an analogy between these DR antigens and the mouse I-E/C antigens.
Alleles↗
Distinct forms of both alpha and beta subunits are present in the human Ia molecular pool.
Two distinct subsets of human Ia molecules, called NG1 and NG2, present in all individuals irrespective of their HLA-DR phenotype, which were previously defined by their reactivity with two monoclonal hybridoma antibodies, D1--12 and D4--22, were analyzed by two-dimensional peptide mapping techniques. Results show that, in the Ia molecular pool from a single individual, small beta subunits of the NG1 and NG2 subsets display significant differences from each other. In addition, beta subunits of the same subset from two different allotype Ia molecular pools are also different from each other, thus indicating that NG1 and NG2 subsets carry polymorphic specificities. Moreover, large alpha chains of NG1 and NG2 subsets are different from each other; however, no significant differences are observed in alpha chains of the same subset when different allotype Ia pools are analyzed. The possible genetic implications of these findings are discussed.
Antibodies, Monoclonal↗
A monoclonal antibody to antigens expressed on MLR-activated T cells inhibits granulocyte macrophage colony formation.
A monoclonal antibody specifically reactive with MLR-activated T cells (MLR2) was added to light density normal marrow cells, depleted of adherent cells and T lymphocytes, and plated in soft agar for granulocyte macrophage colony formation. Colonies from MLR2-treated marrow cells were reduced to less than 10% of expected growth. The inhibition was not complement dependent, did not require the continuous presence of MLR2 in culture, and could not be detected also when human placenta-conditioned medium was used in the place of leukocyte feeder layers as a source of colony-stimulating factor (CSF). Co-culture experiments with MLR2 treated and untreated marrow cells further excluded the possibility of an indirect effect of MLR2 on CFU-c via auxiliary cells. The results of this study suggest that myeloid progenitor cells express a lymphoid antigen that is absent on resting or activated B cells and on resting T cells, but is expressed on activated T cells.
Absorption↗
Localization and biosynthesis of NADH-cytochrome b5 reductase, an integral membrane protein, in rat liver cells. II. Evidence that a single enzyme accounts for the activity in its various subcellular locations.
NADH-cytochrome b5 reductases of rat liver microsomes, mitochondria, and heavy and light Golgi fractions (GF3 and GF 1+2) were compared by antibody inhibition and competition experiments, by peptide mapping, and by CNBr fragment analysis. The water-soluble portion of the microsomal enzyme, released by lysosomal digestion and purified by a published procedure, was used to raise antibodies in rabbits. Contaminant antimicrosome antibodies were removed from immune sera by immunoadsorption onto the purified antigen, and the F(ab')2 fragments of the pure antireductase antibody thus obtained were found to inhibit the NADH-cytochrome c reductase activity equally well in the four membrane fractions investigated, with similar dose-response relationships. Moreover, the purified water-soluble fragment of microsomal reductase, which by itself is very inefficient in reducing cytochrome c, competed for antibody binding with the membrane-bound enzymes, and therefore prevented the inhibition of their activity not only in microsomes but also in the other fractions. The reductases isolated from detergent-solubilized microsomes, mitochondria, GF3, and GF1+2 by immunoadsorption had identical mobilities in SDS polyacrylamide gels. The corresponding bands were eluted from gels, fragmented with pepsin or CNBr treatment, and the two families of peptides thus obtained were analyzed by two-dimensional mapping and SDS polyacrylamide gel electrophoresis, respectively. Both analyses failed to reveal differences among reductases of the four fractions. These findings support the hypothesis that NADH-cytochrome b5 reductase in its various subcellular locations is molecularly identical.
Animals↗
Presence of serum IgD and IgD-containing plasma cells in the mouse.
A new technique which makes use of anti-delta-specific allo-or heteroantisera coupled to Sepharose 4 B has been employed to investigate the presence of IgD molecules in the sera of three mouse strains. The sera were reacted with the insoluble immunosorbents, and the eluted material was labeled with 125I prior to antigenic or sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. This material reacted with anti-delta or anti-L chain reagents, but not with other anti-class-specific antisera and, after reduction, was resolved in three discrete bands in SDS-PAGE. The fastest of these bands comigrated with L chain, whereas the other two moved identically to mouse lymphocyte surface delta chains. Immunofluorescence studies on fixed smears of spleen and Peyer's patches' cells revealed the presence of a small but consistent number IgD-containing plasma cells.
Animals↗
Mercury vapor as a contaminant of hospital environment.
Surveys for airborne mercury in two Ottawa hospitals have been conducted. Two different analytical methods were used. Although the concentrations of mercury vapor were below the TLV, all samples analyzed showed measureable amounts of mercury to be present. Predominant sources of mercury contamination are broken thermometers and sphygmomanometers.
Air Pollutants↗
Characterization of IgD. II. Molecular forms of IgD in human B cells.
Endogenous and surface labeling techniques were used on human lymphoid cells to characterize intracytoplasmic, membrane and secreted IgD, IgD synthesized by lymphocytes and inserted into the cell membrane displayed a single molecular form with the same mobility in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) as the previously described slow migrating serum IgDl. Plasma cells produced and secreted IgDl and another IgD corresponding to the faster-moving serum IgD2. Conversion of one molecular form into the other was never observed, thus indicating that neither molecule is a precursor or a degradation product of the other.
Autoradiography↗
Characterization of IgD. I. Isolation of two molecular forms from human serum.
Human IgD present in the serum of normal individuals or of patients with Hodgkin's disease (having high IgD concentrations) was characterized and compared with five IgD myeloma proteins. IgD was isolated using a highly specific anti-delta insoluble immunoabsorbent from which the bound material was eluted with sodium dodecyl sulphate (SDS) or urea. The latter reagent could be removed by extensive dialysis, thus making possible the renaturation of the eluted molecules. The purity of the IgD thus isolated was confirmed by antigenic analysis. Both kappa and lambda light chain determinants were present on serum IgD, although lambda light chain was predominant with a ratio over the kappa chain of 2:1. SDS-polyacrylamide slab gel electrophoresis analysis revealed two different molecular forms of serum IgD, one (IgD) migrating identically to monoclonal IgD, the other (IgD2) having a faster mobility. The difference between the two molecules was entirely, due to the different sizes of their constituent delta chains. Peptide mapping of the two chains (delta1 and delta2 respectively) and of the delta chain of an IgD myeloma protein was carried out using 125I-labelled material. The three molecules displayed a high degree of homology, the delta2 chain differing by the presence of three characteristic extra peptides. The significance of these extra peptides is discussed in the light of the peptide mapping technique employed.
Autoradiography↗
Correlation of serum IgD level with clinical and histologic parameters in Hodgkin disease.
The concentration of serum IgD was measured in 100 patients with Hodgkin disease; 65 had 3--50-fold increases in IgD levels. Several parameters were found to influence serum IgD concentration: IgD level in older patients (greater than 50 yr) was significantly lower than in the younger patients (P less than 18 yr). IgD concentration was significantly higher in splenectomized than in nonsplenectomized patients (p less than 0.005). Therapy was found to depress IgD concentration, which fell to a value significantly lower than in untreated patients (p less than 0.05). An interesting correlation was found between IgD levels and histologic type of the disease, lower levels being preferentially associated with the lymphocyte predominance type and higher with the lymphocyte dipletion type. The logarithms of the means of these two groups were significantly different from the overall mean of the disease (p less than 0.05 and p less than 0.0005, respectively). Mixed cellularity and nodular sclerosing showed intermediate values.
Aging↗
Radioimmunoassay and chemical properties of glucose 6-phosphate dehydrogenase and of a specific NADP(H)-binding protein (FX) from human erythrocytes.
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Amino Acids↗
Lymphocyte membrane immunoglobulins: similarities between human IgD and mouse IgD-like molecules.
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Animals↗
Biosynthesis and characterization of intracellular IgDkappa in a case of CLL.
A case of chronic lymphocytic leukaemia (CLL) with diffuse intracellular IgDkappa is reported. No serum paraprotein or urinary Bence-Jones protein were detected. No surface immunoglobulin was found on the neoplastic lymphocytes, but the cells had receptors for Fcgamma and the C3 component of complement consistent with other cases of CLL. Biosynthetic studies confirmed that the cells synthesized IgDkappa but there was no evidence for secretion of IgD into the culture medium. The cells did not produce Ig of any other class. The intracellular IgD occurred predominantly as deltakappa units with no covalent links between the chains. These findings are discussed.
Binding Sites, Antibody↗
Increased serum IgD concentrations in patients with Hodgkin's disease.
Serum IgD concentrations have been determined in twenty-one patients with Hodgkin's disease, in eight patients with non-Hodgkin's lymphomas and in twenty-eight normal (control) individuals by both a solidphase radio-immuno-assay and radial-immunodiffusion. Fourteen of the Hodgkin's patients displayed three to forty-five-fold increased serum IgD levels as compared to control individuals, while in the remaining seven patients IgD concentrations were practically normal. Patients with non-Hodgkin's lymphomas had decreased IgD concentrations.
Hodgkin Disease↗
Membrane Ig on MPC11 myeloma cells: correlation between the expression of membrane Ig, a receptor for Ig and the process of secretion.
The expression of membrane immunoglobulin (mIg) was examined in three cloned MPC11-derived mouse myeloma cell lines. Membrane immunofluorescence studies demonstrated that IgG2b producer cells (P1) had complete IgG molecules, L-chain producer (L1) had only L-chain determinants and nonproducer (NP2) did not have any Ig determinants on the cell surface. An Ig receptor, with characteristics different from B lymphocyte Fc receptor, has been found to be present on secreting cells (P1 or L1), but not on the NP2 cell variant. The data reported in the present paper indicate that the expression of mIg and of the Ig receptor molecule is clearly correlated with the process of secretion. In the light of previous data reported on Ig secretion, a model is proposed which correlates the process of secretion with the expression not only of mIg, but also of the receptor for Ig.
Binding Sites, Antibody↗
Membrane Ig on human lymphocytes: rate of turnover of IgD and IgM on the surface of human tonsil cells.
The turnover of IgM and IgD molecules present on the membrane of human tonsil cells has been studied using immunofluorescence and peroxidase-catalyzed membrane radioiodination. With the first of the two techniques cells were treated with pronase to remove membrane immunoglobulin (mIg), placed in culture and stained at intervals to check the reappearance of membrane IgD and IgM on the cell membrane. These experiments showed that membrane IgD (in contrast to membrane IgM) are extremely susceptible to proteolysis. Furthermore, cells treated with a concentration of pronase found to be optimal to remove membrane IgM failed to re-express membrane IgD in vitro. The large majority of tonsil lymphocytes has both membrane IgM and IgD. Due to the different behavior of reappearance of the two membrane molecules after treatment with pronase, it was not possible to obtain the simultaneous re-expression of membrane IgM and IgD by the cells "stripped" with pronase. However, the two molecules were re-expressed in vitro by the cells treated with different pronase concentrations with a similar timing, i.e. 50% or more of the cells re-expressed membrane IgD and IgM after 8 h in culture. 131I-radioiodinated membrane IgD and IgM were also released from the cell surface with a similar timing, the half-life of permanence on the cell membrane being about 4 h for both molecules. These findings thus indicate that IgM and IgD molecules have a similar turnover and that a cell is capable of placing two different Ig molecules at a time on its surface.
Cells, Cultured↗