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R Laskov

Publications and source records attributed to R Laskov.

At least 37 records · Page 2Linked to original sources
PubMed1986

A new autoreactive monoclonal antibody specific for the Thy-1 antigen.

The present study describes the development of a new IgM monoclonal autoantibody reactive with the Thy-1 antigen. The C16-31 monoclonal antibody (mAb) was considered as autoreactive because it reacted with thymus cells of both the C3H and BALB/c strains, which were involved in the development of the antibody. The antibody was reactive with thymus cells in both immunofluorescent and cytotoxic tests. It also showed a weak immunofluorescent reactivity with peripheral T-lymphocytes. The identification of the specificity detected by the C16-31 mAb as the Thy-1 antigen was based on the following criteria: C16-31 mAB displayed a preferential reactivity with Thy-1.2 bearing thymus cells, rather than with Thy-1.1 bearing thymus cells. The tissue distribution of the antigen detected by the C16-31 antibody by direct tests and by direct tests and by adsorption experiments was in accordance with that characteristic for Thy-1. It was high on brain tissue and on thymus cells, and considerably lower on peripheral T-lymphocytes. Coating of thymocytes with C16-31 antibody blocked their reactivity with other monoclonal Thy-1 antibodies. Conversely, coating of thymus cells with rabbit anti-brain serum (RABR) inhibited the binding of C16-31. The C16-31 mAb differed from the Thy-1 autoantibodies described previously in its relatively strong reactivity with brain tissue and its considerably weaker reactivity with peripheral T-lymphocytes. Moreover, C16-31 mAb showed a preferential allospecificity for Thy-1.2, only in its reactivity with thymocytes. In contrast, it reacted equally well with brain tissue from either Thy-1.2 or Thy-1.1 mice.

Animals↗
PubMed1985

Use of a monoclonal, anti Plasmodium berghei antibody, cross reacting with P. falciparum, for the detection of P. falciparum in in vitro infected blood.

This report describes an immunoradiometric assay for Plasmodium falciparum in infected blood, based on a cross-reacting monoclonal antibody (mAb) raised against P. berghei. In this assay, binding of the mAb to intact P. berghei parasites coated on microtiter plates is inhibited by solubilized P. falciparum infected red blood cells. The use of P. berghei parasites in conjunction with monoclonal antibodies should facilitate the development of an inexpensive and reproducible test for the immunodiagnosis of malaria.

Animals↗
PubMed1984

Monoclonal autoantibodies to histones from autoimmune NZB/NZW F1 mice.

Fusion of spleen cells from autoimmune NZB/NZW female mice with drug-resistant myeloma cells (clones NSI/1, X63-Ag8.653 and NSO/1) produced hybrid clones which secreted antibodies to various nuclear components. Roughly 50% of the anti-nuclear hybridomas produced antibodies reacting with DNA, 20% with RNA and 30% reacted with other nuclear antigens. Two hybridomas of the latter group were cloned and studied in detail. They secreted antibodies which produced bright fluorescence staining of nuclei and metaphase chromosomes. The specificity of the antibodies was determined by testing them in an enzyme-linked immunosorbent assay and a radioimmunoassay against individual acid- and salt-extracted histones, against histones mixed two and three at a time and against histone complexes isolated as such from chromatin. One of the monoclonal antibodies was specific for histone H2B and reacted with the histone free in solution or when present as a H2A-H2B complex. The second monoclonal antibody recognized a specific conformation in the H3-H4 complex that was present only when the complex was obtained from chromatin by salt extraction. The same conformation, however, could be induced by adding histone H2B to a mixture of acid-extracted H3 and H4. Our findings show that the autoimmune syndrome in NZB/NZW mice resembles human systemic lupus erythematosus not only in the incidence of antibodies to DNA and RNA, but also in the production of autoantibodies to histones.

Animals↗
PubMed1984

Establishment of cell lines from somatic cell hybrids between human monocytes and mouse myeloma cells.

To study human monocyte functions, we attempted to immortalize human monocytes by producing somatic cell hybrids between such monocytes and the mouse myeloma cell line NSI. In this study we report the successful establishment of eight hybrid cell lines that have been grown in culture for more than a year, and some of them retained part of the human chromosome complement, as well as monocyte markers and activities. Karyotype analysis of these hybrid lines revealed that cells of seven out of eight of the lines contained one to 16 human chromosomes and in four of them, more than nine human chromosomes were observed. Several of the cell lines expressed monocytic markers and functions. Thus, in two of the hybrid lines nonspecific esterase could be demonstrated in 10 to 29% of the cells, and Fc receptors were demonstrated in three of the hybrid cell lines. Significant levels of human ferritin were detected in one of the lines, and two other cell lines secreted interleukin 1-like substance into the culture medium. These results encourage us to use human-mouse somatic cell hybridization as an approach for the establishment of human monocyte cell lines, which will preserve their functions and produce monocyte-derived factors.

Animals↗
PubMed1983

Simultaneous expression of mu- and gamma-chain mRNA in cloned murine B-lymphoma cell lines.

The expression of immunoglobulin heavy chain genes was studied in five murine B-lymphomas known from previous studies to express either mu (38C-13), mu + delta (L10A, K46, BCL1) or gamma chains (A20). The presence of mu- and gamma-mRNAs in these tumors was determined by Northern blot analyses of the total cell poly(A)+ mRNA, using the appropriate 32P-labeled recombinant plasmid probes. In four out of the five lymphomas examined, both mu- and gamma-mRNAs were detected. The mu-mRNA appeared as multiple discrete bands of 1.9-3.0 kb. In three out of the four lymphomas, the gamma-mRNA appeared as two bands, a major one of 1.9 and a minor one of 3.9 kb. Three myelomas examined by similar methods did not contain more than one class of heavy chain mRNA. Reexamination of the Ig chains produced by the B-lymphomas which expressed both mu- and gamma-mRNAs revealed that two of them preserved their original phenotype and expressed mu (38C-13) or gamma chains only (A20). In contrast, two of the cell lines previously shown to express mu but not gamma chains (i.e., L10A and K46R) had changed during growth in culture and 'switched' to the production of gamma chains only. These results indicate that, in contrast to myelomas, B-lymphomas possess two classes of mRNA. However, the production of heavy chain mRNA in B-lymphomas is not necessarily accompanied by synthesis of the corresponding polypeptide chains. More studies are necessary to find out whether the expression of 'non-productive' heavy chain mRNA molecules in B-lymphomas is related to the phenomena of 'allelic exclusion' and/or the 'heavy chain switch' which occurs during the maturation of B-cells.

Animals↗
PubMed1983

The role of E receptors in the attachment of thymocytes and T lymphocytes to human target cells.

Human thymocytes, activated T lymphocytes, and neuraminidase-treated T cells possess the distinct capacity of forming conjugates with various human cell lines. The present study investigated whether E receptors, which endow human T cells with their capacity to bind sheep red blood cells (SRBC), are involved in this phenomenon. Monoclonal antibodies to human T cells and various simple sugars were studied for their effect on the attachment of human T cells to target cells. A-22, a monoclonal antibody to the E receptor, inhibited the formation of E rosettes by T cells and SRBC, and reacted in immunofluorescent-staining assays with the majority of human thymocytes and peripheral T cells, and with T-cell lines capable of forming E rosettes. When human thymus cells were treated with A-22 antibody they showed a reduction of up to 70% in their capacity to attach to the GM-4762 lymphoblast cell line and the K-562 myeloid line. Antibody treatment of the target cells, rather than of the thymus cells, had no effect on the formation of conjugates between thymus cells and target cells. Treatment of thymus cells with various monoclonal antibodies to T cells which do not react with the E receptor had no inhibitory effect. The exposure of human thymus cells to various simple sugars (D-mannose, D-fucose, galactose, and lactose) markedly reduced their capacity of forming conjugates with target cells. Exposure of neuraminidase-treated peripheral blood lymphocytes and of activated T cells to A-22 antibody inhibited their attachment to human target cells. The present study suggests that E receptors play a role in the attachment of human thymus cells and activated T cells to other human cells, and raises the possibility that these T-cell receptors may be involved in the process of recognition of "self" structures by human T lymphocytes.

Antibodies, Monoclonal↗
PubMed1982

Antibodies to RNA from autoimmune NZB/NZW mice recognize a similar antigenic determinant and show a large idiotypic diversity.

We have identified two RNA-specific hybridoma autoantibodies in fusions of spleen cells from unimmunized NZB/NZW female mice with BALB/c myeloma cells. The two fusion experiments were carried out 2 years apart with different myeloma partners. Specificity analyses showed that the two monoclonal antibodies and the total RNA-binding IgG in NZB/NZW serum recognize a G,C-rich sequence of ribonucleotides. The isolated heavy and light chains of the two antibodies and their papain Fab fragments could be distinguished by NaDodSO4/polyacrylamide gel electrophoresis. Rabbit anti-idiotypic antibodies prepared against the two monoclonal proteins showed unique specificities for the antigen-binding sites of their cognate auto-antibodies. Moreover, the anti-idiotypic antisera had little effect on the RNA-binding capacity of the total IgG from NZB/NZW serum. These results suggest that a wide range of different idiotypes is involved in the autoimmune response to a similar antigenic determinant.

Animals↗
PubMed1981

Membrane immunoglobulins of spontaneous B lymphomas of aged BALB/c mice.

Four cell lines derived from spontaneous BALB/c lymphoma tumors were analyzed with regard to the type of their membrane immunoglobulins (Ig). Using lactoperoxidase iodination of membrane proteins combined with immunoprecipitation and electrophoresis on polyacrylamide gel, three of these cell lines (X16c, L10A and K46) were found to express the monomeric form of IgM and IgD as well as half molecules. One cell line (M12) lacked both IgM and IgD. The apparent mol. wt of the lymphoma micro chain was about 80 000 and exceeded the mol. wt. of 75 000 determined for micro chains secreted by myeloma cells. The mol. wt. of the delta heavy chain was found to be 66 000. Immunofluorescence showed that the L10A and X16c lines expressed lambda light chains on their cell surface. Another Ig-bearing cell line (K46) expressed both lambda and kappa chains. Thus, three out of the four B lymphomas examined expressed both IgM and IgD with light chains of the Lambda type. These results, together with our previous findings which demonstrate the presence of Ia and Fc receptors on the same cells, indicate that spontaneous B lymphomas in BALB/c mice are the malignant counterpart of mature B lymphocytes.

Aging↗
PubMed1981

Effect of iron deficiency on transplantable murine plasmacytoma.

The effect of iron deficiency on tumour growth and on host survival was studied in BALB/c mice with transplanted Merwin Plasma Cell-II tumors. Iron deficiency was induced by maintaining the animals on an iron-free diet consisting of milk-cornflour supplemented with CuCl2 and vitamins A and D. Iron deficiency resulted in retardation of both body and tumor growth in weanling BALB/c mice. Their survival, however, was not significantly different from that of iron supplemented controls. The inhibitory effect of iron deficiency on host and tumour growth could not be reproduced in adult BALB/c mice. The survival of tumor-bearing hosts maintained on a milk-cornflour diet (whether supplemented with iron or not) was significantly longer than that of animals maintained on a purina diet.

Animals↗
PubMed1980

Inhibition of cell-mediated lysis by xenoantibodies reactive with effector T lymphocytes.

The aim of the present study was to determine whether rabbit antisera against various murine tissue antigens contain antibodies that affect the activity of cytotoxic T lymphocytes in the absence of complement. Following heat inactivation, the xenoantisera were absorbed with mouse liver and kidney and tested for their capacity to inhibit cell-mediated lysis (CML). In the presence of complement (C), rabbit anti-brain antiserum (RABr), rabbit anti-thymus antiserum (RAT) and rabbit anti-boiled thymus antiserum (RABT) lysed effector T cells, and CML was abolished. In the absence of C, RAT maintained its strong inhibitory activity on CML, RABr had no inhibitory effect, whereas only some batches of RABT were effective. Monovalent Fab fragments of RAT inhibited CML as effectively as intact antibody molecules. The activity of RAT could be removed by absorption with T and B lymphocytes of various sources. Inhibitory antibodies could be removed by absorption with C3 H B lymphoma cells and upon elution from antibody-coated cells proved again highly effective in inhibiting CML. These results show that RAT contains antibodies which react with determinants shared by T and B lymphocytes and which block the activity of cytotoxic T cells.

Animals↗
PubMed1980

A ribonucleic acid-specific antibody produced during autoimmune disease: evidence for nucleotide sequence specificity.

A hybridoma secreting RNA-binding autoantibody has been produced by fusion of spleen cells from autoimmune NZB/NZWF1 mice with drug-resistant IgG2b-producing myeloma cells from BALB/c mice. Studies on the specificity of the purified monoclonal autoantibody revealed: (a) absolute specificity for ribopolynucleotides as compared with deoxyribopolynucleotides; (b) specificity for single-stranded RNA as compared with double-stranded RNA; (c) high affinity for the random copolymer poly(G, C); and (d) preference for the random heteropolymer poly(G, C, U). These studies were complemented by stoichiometric measurements of the antibody-RNA complex and computer analysis of the abundance of various di-, tri- and tetranucleotide sequences in native RNA. Taken together, these data suggest that the antigenic determinant recognized by the monoclonal autoantibody is largely composed of a trinucleotide sequence of single-stranded RNA containing, G, C and U residues.

Animals↗
PubMed1980

A high production rate of translatable IgG mRNA accounts for the amplified synthesis of IgG in myeloma cells.

The aim of the present work was to determine whether the accumulation of Ig mRNA in myeloma cells is due to a high rate of production or to a high stability of these molecules. Specific mRNAs for the light and heavy polypeptide chains of IgG were isolated from the murine MPC-11 myeloma tumor cells by immune precipitation of polysomes which synthesize these chains. It was found that the immune-precipitated polysomes were enriched 10--30-fold in the gamma and chi mRNA sequences respectively. In the wheat germ cell-free system the chi mRNA preparation was translated mainly into three polypeptides of Mr 25 000, 18 000, and 15 000. The method of immune precipitation of polysomes was also used to characterize three variant clones of MPC-11 myeloma. It was found that little if any gamma-chain polysomes are present in the L-chain producer and non-producer clones, while a substantial amount of chi-chain polysomes was present in the non-producer clone. This may be due to the presence in the non-producer cells of the constant region chi-chain fragment. In order to determine the relative synthesis rate of chi and gamma mRNAs, pulse-labelled polysomes were immune precipitated using antibodies to chi and gamma chains. It was found that chi and gamma mRNA molecules are produced at a very high relative rate each accounting for 10--15% of the total labeled mRNA after 1 h of labeling. These values are higher than the steady-state pool size of chi and gamma mRNA, which was 5--6%, and indicates that the half-life of these molecules is not unusually high. It is concluded that the amplified synthesis of immunoglobulin chains in myeloma cells is mainly due to a high rate of production of translatable chi and gamma mRNAs.

Animals↗
PubMed1980

A hybridoma from an autoimmune NZB/NZW mouse producing monoclonal antibody to ribosomal-RNA.

Spleen cells from an unimmunized autoimmune NZB/NZW F1 female mouse were fused to the BALB/c MPC-11 drug-resistant clone 45.6 TG 1.7. One hybrid clone (D4) produced IgG-3 immunoglobulin that bound ribosomal RNA. A high concentration of this antibody was produced in the ascitic fluid of NZB/NZW male mice. DNA, tRNA, and synthetic single- and double-stranded polynucleotides could not bind significantly to the antibody. A Scatchard analysis showed that the rRNA-binding immunoglobulin is monoclonal and has a high affinity (10(9) liter/mole) for the RNA antigen.

Animals↗
PubMed1979

The effect of xenoantisera on T-lymphocyte functions in the absence of complement.

An attempt was made to determine whether xenoantisera can detect functional receptors on mouse T lymphocytes. Antisera were raised by immunizing rabbits with BALB/c thymus cells, boiled thymus homogenate, brain homogenate or bone marrow cells. Following heat inactivation these antisera were absorbed with mouse kidney and liver homogenates, and studied for their effect, in the absence of C', on the activity of murine T lymphocytes. Rabbit anti-bone marrow serum (RAB) had no effect on the mixed lymphocyte reaction (MLR) nor on cell-mediated lysis (CML). In contrast, rabbit anti-thymus serum (RAT) and anti-boiled thymus serum (RABT) inhibited strikingly, the MLR, CML, and the response to concanavalin A and phytohemagglutinin. Rabbit anti-brain serum (RABR) caused a marked increase of the proliferation of lymphocytes both in the presence or absence of various stimuli and had no effect on the CML. Absorption experiments indicated that a number of antigens are involved in the inhibitory activity of RAT. Antibodies to a T cell specific antigen interfere with the response of T lymphocytes to mitogenic stimuli, while the activity of cytotoxic T cells is inhibited by antibodies to a determinant shared by B and T lymphocytes.

Absorption↗
PubMed1979

Induction of amplified synthesis and secretion of IgM by fusion of murine 'b lymphoma with myeloma cells.

Murine B lymphoma cultured cell lines bearing membrane IgM and lacking the ability to secrete measurable amounts of IgM were fused with drug-resistant cell lines derived from the IgG2b-producing MPC-11 myeloma. Many of the hybrid clones synthesized and secreted large amounts of IgM, as judged by radial and double immunodiffusion in agar of culture supernatants and by polyacrylamide gel electrophoresis of biosynthetically labeled IgM. When fused with an IgG2b-producing myeloma, many of the hybrids also produced IgG2b, indicating that there was no suppression of the parental IgG synthesis in the hybrids. The amount of IgM or IgG2b secreted by the hybrids was higher than that secreted by myeloma cell lines. The synthesis of the gamma2b heavy chain of the MPC-11 myeloma was not reexpressed by fusion of a gamma2b nonproducer myeloma cell variant with B lymphoma. No other classes of Ig heavy chains, besides the gamma2b and the mu chains, were found to be secreted by any of more than 100 B lymphoma--myeloma hybrids examined. The results of the present work suggest that myeloma cells may fuse not only with normal plasma cells but also with less-mature normal B lymphocytes and that this fusion "induces" the maturation of B lymphocytes into IgM-secreting cells.

Animals↗