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H G Ljunggren

Publications and source records attributed to H G Ljunggren.

At least 109 records · Page 6Linked to original sources
PubMed1991

Differential mRNA levels of c-myc, c-fos and MHC class I in several clones of a murine fibrosarcoma.

We have evaluated the relationship between MHC class-I, c-myc and c-fos proto-oncogene expression in several clones of a methylcholanthrene-induced fibrosarcoma (GR9) which originated in a BALB/c mouse. These clones represent a heterogeneous population and differ markedly with regard to H-2 class-I cell-surface expression, local tumor growth, NK sensitivity and metastatic potential. In the present study we show that cell-surface expression of MHC class-I antigens correlates inversely with levels of c-myc mRNA transcripts. On the other hand, mRNA levels of c-fos are correlated directly with the amount of mRNA of MHC class I. Treatment of the B9 clone with gamma interferon increased mRNA transcription and surface expression of H-2 class-I antigens, while c-myc transcription was simultaneously down-regulated. In contrast, c-fos mRNA levels remained unaltered.

Animals↗
PubMed1991

Recognition of beta 2-microglobulin-negative (beta 2m-) T-cell blasts by natural killer cells from normal but not from beta 2m- mice: nonresponsiveness controlled by beta 2m- bone marrow in chimeric mice.

The role of major histocompatibility complex (MHC) class I expression in control of the sensitivity of normal cells to natural killer (NK) cells was studied by the use of mutant mice made deficient for expression of beta 2-microglobulin (beta 2m) through homologous recombination in embryonal stem cells. T-cell blasts from beta 2m-deficient (beta 2m -/-) mice were killed by NK cells from normal mice in vitro, while beta 2m +/- blasts were resistant. The beta 2m defect also affected the NK effector cell repertoire: NK cells from beta 2m -/- mice failed to kill beta 2m -/- blasts, while they retained the ability to kill the prototype NK cell target lymphoma YAC-1, although at reduced levels. The inability to recognize beta 2m -/- blasts could be transferred with beta 2m -/- bone marrow to irradiated beta 2m-expressing mice. In contrast, the development of CD8+ T cells (deficient in beta 2m -/- mice) was restored in such chimera. These results indicate that loss of MHC class I/beta 2m expression is sufficient to render normal cells sensitive to NK cells, and that the same defect in the hemopoietic system of a mouse renders its NK cells tolerant to beta 2m-deficient but otherwise normal cells. In the beta 2m -/- mice, NK cells may be selected or educated by other bone marrow cells to tolerate the MHC class I deficiency. Alternatively, the specificity may be controlled directly by the class I molecules on the NK cells themselves.

Animals↗
PubMed1991

Alteration of the natural killer repertoire in H-2 transgenic mice: specificity of rapid lymphoma cell clearance determined by the H-2 phenotype of the target.

The mechanism behind natural tumor resistance conveyed by a H-2Dd transgene to C57Bl/6 (B6) mice was investigated. Transgenic D8 mice were more efficient than control mice in natural killer (NK) cell mediated rapid elimination of intravenously inoculated radiolabeled lymphoma cells of B6 origin, such as RBL-5. There was no difference between D8 and B6 mice when elimination of YAC-1 targets was monitored. The effect of the transgene on the NK repertoire was related to the H-2 phenotype of the target: the differential elimination of RBL-5 lymphoma cells in D8 and B6 mice was not seen when a H-2 deficient variant of this line was used (efficiently eliminated in both genotypes), nor was it seen with a H-2Dd transfectant (surviving in both genotypes). The data show that a MHC class I transgene can directly control natural killing in vivo by altering the repertoire rather than the general levels of NK activity. Since the NK mediated elimination seen after introduction of a novel gene in the host was neutralized by introducing the same gene (H-2Dd), but not an unrelated class I gene (H-2Dp), in the tumor, the data support the concept of NK surveillance against missing self. This combined transgenic/transfectant system may serve as a tool for a molecular dissection of the interactions between NK cells and their targets in vivo.

Animals↗
PubMed1991

Different types of allospecific CTL clones identified by their ability to recognize peptide loading-defective target cells.

Allospecific immune responses against the MHC of another individual are remarkably strong, due t a high number of responding T cell clones. Although it has been demonstrated that some allospecific cytotoxic T lymphocytes (CTL) recognize peptides presented by allogeneic MHC class I molecules, it has remained unclear whether MHC molecules can be recognized directly. We used the H-2b-derived murine lymphoma mutant RMA-S, which has a defect affecting peptide loading of class I molecules, to test whether recognition by allospecific CTL always requires the presence of peptides. Three types of anti-H-2Kb CTL clones can be distinguished by their ability to lyse RMA-S target cells. Type A CTL clones efficiently lyse these target cells, the lysis by type B CTL clones is inefficient, and type C clones fail to lyse RMA-S. Up-regulation of the levels of H-2Kb density improved lysis by type B clones, but did not lead to lysis by type C clones. Some type A and B CTL clones apparently can recognize class I molecules devoid of peptides, while others are likely to recognize peptides which are not affected by the presentation defect of RMA-S. We suggest that type C clones are specific for peptides which are not presented by the mutant cells. The results show that the majority of alloreactive CTL recognize peptide/MHC complexes, while some CTL behave as if they can recognize class I molecules in the absence of MHC-bound peptides.

Animals↗
PubMed1991

The RMA-S lymphoma mutant; consequences of a peptide loading defect on immunological recognition and graft rejection.

Experiments with mutant cell lines have underscored the role for peptide in maintenance of the structure of major histocompatibility complex (MHC) class-I molecules. The class-I molecules act as receptors for antigenic and "self" peptides derived from degraded intracellular synthesized proteins. The class-I/peptide trimeric complex is transported to the cell surface where it is scrutinized by cytotoxic T lymphocytes (CTL). The murine RMA-S mutant cell lines have a defect in class-I assembly and express markedly reduced levels of class-I molecules at the cell surface. The mutation is consistent with a defect in peptide transport from the cytosol to the place of assembly with class-I molecules. Addition of synthetic peptides to RMA-S cells and RMA-S cell lysates stimulates assembly of the class-I molecules and indicates that peptide plays a crucial role in attaining the class-I structure. Recent findings have demonstrated that class-I heavy clains (HCs) and beta 2 microglobulin (beta 2m) can assemble in absence of synthetic peptides, forming presumably "empty" (non-peptide-containing) class-I dimeric complexes, in RMA-S cells cultured at reduced temperature. The few class-I molecules present on RMA-S cultured at physiological temperature share the phenotype of "empty" class-I molecules induced at reduced temperature. This finding has allowed the re-interpretation of earlier studies and opened new ways to analyze the interaction between MHC-class-I molecules and different effector cells such as allo-specific CTLs, class-I-restricted CTLs and natural killer (NK) cells. In addition, recent data also suggest that RMA-S represents an attractive model for examining direct class-I-peptide interactions on intact cells or in cell lysates.

Animals↗
PubMed1991

Antigen presentation and the association of class-I molecules.

We have identified two mutant cell lines which are not able to present epitopes of influenza virus synthesized in the cytoplasm but can present the same epitope when exposed to it as a peptide in the extracellular medium. The cell lines also have a defect in class-I assembly, with reduced expression of assembled alpha chain: beta 2M heterodimers at their cell surface. This led to the suggestion that the two traits were the result of the same mutation and that stable assembly of class-I molecules is dependent on peptide binding. Consistent with this idea was the finding that exposure to specific peptides in the extracellular fluid promotes stable association of class-I heavy chains with beta 2M and restores expression of class-I at the cell surface. We have gone on to show that stable assembly of class-I molecules can be supported in detergent extracts of the mutant cells when specific peptides are added. Peptides stabilized a conformational change in the class-I heavy chain and association with beta 2M by binding to the complexes. This effect is apparent at peptide concentrations around 100-fold lower than required in "peptide feeding" experiments with whole cells. We have also demonstrated that the conformational change induced in heavy chain is influenced by the concentration of beta 2M, and consequently have been able to demonstrate the formation of empty class-I molecules.

Animals↗
PubMed1990

A weakly tumorigenic phenotype with high MHC class-I expression is associated with high metastatic potential after surgical removal of the primary murine fibrosarcoma.

We have examined the metastatic capacity of different clones of a chemically induced fibrosarcoma GR9. These clones have previously been characterized for their H-2 class-I and class-II phenotype, NK sensitivity and local tumor growth. Our present data show that clones which express low amounts of H-2 class-I antigens are poorly metastatic in a post-surgical spontaneous metastasis assay, while those expressing high levels of class-I antigens possess a high metastatic capacity. These results correlate inversely with local growth patterns of the clones. High metastatic capacity was associated with resistance to NK cells. In an experimental metastasis assay, based on intravenous administration of in vitro carried GR9 clones to syngeneic BALB/c mice, an opposite result to the post-surgical assay was obtained. Gamma-IFN treatment of B9 clones (H-2-deficient) enhanced H-2 class-I expression and diminished experimentally induced metastases. Metastatic colonies, from the spontaneous metastasis assay, obtained from different organs, showed changes in the ratio H-2K/H-2D. There was a tendency for down-regulation of the expression of H-2K molecules in H-2-positive clones and for up-regulation of H-2D expression in H-2-negative clones.

Animals↗
PubMed1990

Empty MHC class I molecules come out in the cold.

Major histocompatibility complex (MHC) class I molecules present antigen by transporting peptides from intracellularly degraded proteins to the cell surface for scrutiny by cytotoxic T cells. Recent work suggests that peptide binding may be required for efficient assembly and intracellular transport of MHC class I molecules, but it is not clear whether class I molecules can ever assemble in the absence of peptide. We report here that culture of the murine lymphoma mutant cell line RMA-S at reduced temperature (19-33 degrees C) promotes assembly, and results in a high level of cell surface expression of H-2/beta 2-microglobulin complexes that do not present endogenous antigens, and are labile at 37 degrees C. They can be stabilized at 37 degrees C by exposure to specific peptides known to interact with H-2Kb or Db. Our findings suggest that, in the absence of peptides, class I molecules can assemble but are unstable at body temperature. The induction of such molecules at reduced temperature opens new ways to analyse the nature of MHC class I peptide interactions at the cell surface.

Animals↗
PubMed1990

Transfection of beta 2-microglobulin restores IFN-mediated protection from natural killer cell lysis in YAC-1 lymphoma variants.

A beta 2-microglobulin (beta 2m)-deficient variant of YAC-1, A.H-2-, was transfected with a genomic beta 2m clone. Transfected cells were used to investigate the role of beta 2m in IFN-induced protection from NK cell lysis. IFN-gamma treatment of the NK-sensitive murine YAC-1 lymphoma results in reduced sensitivity to NK cell-mediated lysis in parallel with increased expression of its constitutively low MHC class I expression. It was previously shown that the A.H-2- variant had lost both these capacities, although it retained other responses to IFN-gamma. Here beta 2m transfection restored the YAC-1 phenotype with respect to an inducible expression of MHC class I molecules and a concomitant protection from NK cell lysis after treatment with IFN-gamma. In the absence of IFN-gamma the NK sensitivity of the transfectants did not differ significantly from A.H-2-. A similar protection from NK cell lysis, in parallel with enhanced MHC class I expression, was observed for in vivo-passaged beta 2m transfectants whereas no protection was found for in vivo-passaged A.H-2- cells. The present study provides evidence that the IFN-gamma-mediated protection from NK cell lysis is dependent on beta 2m expression in the YAC-1 lymphoma. Restoration of MHC class I assembly, transport, and concomitantly an IFN-gamma augmentable cell surface expression of MHC class I molecules is a possible explanation for the effect of beta 2m.

Animals↗
PubMed1990

Resistance to H-2-restricted but not to allo-H2-specific graft and cytotoxic T lymphocyte responses in lymphoma mutant.

The lymphoma mutant RMA-S escaped graft rejection after transplantation over a minor histocompatibility barrier, whereas it was rejected in H-2 allogeneic mice. The parental control line was rejected in both situations. The mutant, which had been selected against MHC class I molecules retained 5 to 10% of the wild-type H-2Db, Kb, and beta 2-microglobulin expression on the cell surface. It remained sensitive to allo-H-2b CTL in vitro, but was completely resistant to minor histocompatibility antigen-specific, H-2b-restricted CTL. It was equally resistant to other H-2b-restricted responses against internally derived Ag, such as tumor-specific CTL or a CTL clone specific for the influenza virus nucleoprotein. The results indicate a target cell defect that selectively abolishes the sensitivity to H-2-restricted CTL directed against internally processed Ag. This appears sufficient to shift the transplantation response over a minor histocompatibility Ag barrier from rejection to acceptance. There are two possible explanations for the results: 1) a block in the MHC class I-directed pathway for internal Ag processing, and 2) subthreshold H-2/Ag ligand density in relation to triggering requirements of restricted CTL. Regardless of the type of defect, the results demonstrate a difference between allo-H-2-specific and H-2-restricted CTL recognition at the level of the target cell.

Cytotoxicity, Immunologic↗
PubMed1990

Restoration of H-2b expression and processing of endogenous antigens in the MHC class I pathway by fusion of a lymphoma mutant to L cells of the H-2k haplotype.

The RMA-S lymphoma mutant cannot process and present antigens to H-2-restricted cytotoxic T lymphocytes. It synthesizes major histocompatibility complex class I heavy (H-2KbDb) and light beta 2-microglobulin (beta 2mb) chains of normal size and charge, but only a fraction of these assemble and reach the cell surface. As a first step investigating the genetic defect of this line, we have fused it to a L cell fibroblast line (H-2KkDk/beta 2ma). The fusion restored H-2Kb, Db and beta 2mb expression as well as the ability to process and present internally derived (minor histocompatibility and influenza virus nucleoprotein) antigens in RMA-S. This shows that the mutation(s) responsible for the phenotype of RMA-S is (are) not located within the MHC class I heavy and light chain genes. Other cellular factors, derived from the L cell fusion partner, can control antigen processing and transport of MHC class I molecules. These findings are discussed in relation to the observation that assembly and transport of MHC class I molecules can be induced in the mutant by H-2b-restricted peptides. The recessive nature of the defect and its independence of MHC class I genes in the mutant has important implications for future transfection studies, of this and similar mutants, aiming at establishing cells containing non-assembled MHC class I molecules of different alleles and identifying the gene(s) controlling processing of endogenous antigens.

Animals↗
PubMed1990

High-resolution one-dimensional isoelectric focusing of mouse MHC class I antigens. Identification of natural and experimentally induced class I antigens.

A method is described for a biochemical comparison of mouse class I antigens utilizing antisera with a monomorphic pattern of reaction and high-resolution one-dimensional isoelectric focusing (1D-IEF). The most commonly occurring and studied H-2K and D alleles were identified in a comparison of over 40 mouse strains. By comparing H-2 mutant mouse strains, cell lines transfected with defined class I genes, or mice transgenic for a mouse class I gene and H-2 recombinant mouse strains, unambiguous identification of class I alleles was possible. The complex pattern presented by H-2-heterozygous mice was readily resolved into the contribution by the individual parental alleles. The H-2b bm series of mutants was analyzed, and for those mutants where a charge difference was predicted based on their known sequence, a change in isoelectric point (IEP) was indeed observed. Based on analysis by IEF, the bm8 mutant may contain (an) amino acid substitution(s) in addition to those reported. The present method further appears useful in elucidating defects in class I antigen synthesis and post-translational modifications, as these cannot be easily characterized when using surface staining with monoclonal antibodies (mAbs).

Alleles↗
PubMed1990

In search of the 'missing self': MHC molecules and NK cell recognition.

Natural killer (NK) cells can defend an organism against a variety of threats, probably using several different strategies to discriminate between normal and aberrant cells. According to the 'missing self' hypothesis, one function of NK cells is to recognize and eliminate cells that fail to express self major histocompatibility complex (MHC) class I molecules. In this article Hans-Gustaf Ljunggren and Klas Kärre review in vivo studies with H-2-deficient targets that support this hypothesis. In vitro studies, some of which have given conflicting results, are interpreted within a multiple choice model for NK cell recognition. The authors derive testable predictions for how MHC class I molecules act in cases where they control a rate-limiting step in the NK cell-target interaction.

Animals↗
PubMed1990

[Molecular analysis of relationship between oncogene (N-myc and c-src) expression and major histocompatibility complex antigen gene expression in mouse neuroblastoma lines].

The authors have investigated the relationship between oncogene (N-myc and c-src) expression and major histocompatibility complex (H-2 in the mouse) antigen gene expression at the molecular levels, by using mouse neuroblastoma sublines (NB-1 and NB-V). Fluorescence-activated cell sorter analysis showed that NB-1 cells exhibited positive expression to H-2 Kk, H-2 Dd, and beta-2-microglobulin, while NB-V cells were negative to all three antigens. It was found that dimethyl sulfoxide (DMSO) had a capacity to increase an H-2 class I antigen expression on NB-1 cells, whereas no change was observed on NB-V cells after DMSO treatment. Molecular analysis with deoxyribonucleic and ribonucleic acid (RNA) blot hybridization and immunoprecipitation revealed that the enhancement of H-2 antigen expression on NB-1 cells was modulated at the transcriptional control of the H-2 gene. In contrast, negative H-2 antigen expression on NB-V cells was caused by block at the level of glycosylation of the H-2 heavy chain, although an increase in messenger RNA of the H-2 gene was induced after DMSO treatment. There was neither amplification nor rearrangement of N-myc and c-src oncogenes in either neuroblastoma subline. Nuclear run-on transcription assay revealed that the N-myc gene was post-transcriptionally down-modulated by DMSO, whereas the c-src gene was transcriptionally up-regulated. It was thus suspected that N-myc and c-src might be directly associated with cellular proliferation and differentiation in neuronal tumors and that in vivo tumorigenicity could be regulated by the control mechanism of oncogene expression in relation to H-2 gene expression on tumor cells.

Animals↗
PubMed1990

[Cytotoxic effector mechanism and genetic control of non-immunized hybrid resistance to mouse T cell lymphoma transplanted outside and inside the brain].

A Moloney virus-induced T cell lymphoma, YAC-1, derived from A/Sn (H-2a) inbred mouse origin, was tested for hybrid resistance (HyR) after subcutaneous (s.c.) or intracerebral (i.c.) tumor cell inoculation into syngeneic and semi-syngeneic mice. The F1 hybrids (H-2a/b) between A/Sn and C57BL/6 mice more strongly resisted the s.c. inoculation of 10(6) and 5 x 10(5) cells than did syngeneic recipients. In contrast, no HyR to the i.c. inoculation of 10(4) and 10(3) cells was seen in the F1 hybrid mice. Natural killer (NK) cell activity was much higher in F1 hybrids than in syngeneic mice. 125I-iododeoxyuridine-labeled YAC-1 cells were more efficiently eliminated from the highly resistant F1 hybrids than from the parental strain in both 4 and 18 hour in vivo rejection assays via intravenous (i.v.) and s.c. injection, respectively. The remaining radioactivity of the brain, however, did not differ between these mice. Thus, there was a correlation between the in vivo resistance of F1 hybrid mice to challenge s.c. inoculation of parental tumors and their expression of lymphocyte-mediated natural cytotoxicity in vitro against those tumors. T cell depletion by thymectomy followed by irradiation and fetal liver reconstitution did not abrogate the s.c. HyR against YAC-1, whereas NK cell depletion by i.v. administration of anti-asialo-GM1 antibodies resulted in the disappearance of the resistance. Furthermore, genotypic study segregating (A/Sn x C57BL/6) F1 x A/Sn backcross mice indicated that the s.c. HyR might be attributable primarily to heterozygosity within the H-2 complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Experimental analysis of anti-tumor cytotoxic mechanism for hybrid resistance to mouse neuroblastoma].

A spontaneous neuroblastoma (NB-85, H-2a/a) was tested for hybrid resistance (HyR) after subcutaneous (s.c.) inoculation into syngeneic and semisyngeneic mice. The hybrids (F1) (H-2a/b) between A/Sn and Leaden mice and the F1 between A/Sn X C57BL/6 mice were more resistant to the s.c. inocula of 10(6) to 5 X 10(5) cells than syngeneic recipients. Thymectomy, followed by irradiation and fetal liver reconstitution, abrogated the HyR against NB-85, whereas intravenous (i.v.) administration of anti-asialo-GM1 antibodies had no influence on the resistance. Surface phenotypic analysis revealed that NB-85 expressed H-2 Kk (-), Dd (+) and beta 2-microglobulin (-), showing a dissociation of the cell surface. Anti-H-2a-specific cytotoxic T lymphocytes exhibited a significant lytic activity against NB-85, while NB-85 was highly refractory to natural killer cell (NK)-mediated lysis. In vivo NK-mediated rejection assays showed that 125I-iododeoxyuridine (IUdR) labeled NB-85 cells were not eliminated more efficiently from the highly resistant F1 hybrids than from the parental strain. Furthermore, genotypic study with segregating (A/Sn X Leaden) F1 X A/Sn backcross mice showed that the HyR was attributable primarily to heterozygosity within the H-2 complex. Taken together, it was suggested that the HyR to an NK-resistant mouse NB-85 neuroblastoma might involve a T cell-dependent immunosurveillance with H-2 genetic control.

Animals↗
PubMed1989

Effect of IFN-gamma treatment and in vivo passage of murine tumor cell lines on their sensitivity to lymphokine-activated killer (LAK) cell lysis in vitro; association with H-2 expression on the target cells.

Interferon-gamma (IFN-gamma) treatment or in vivo passage of the murine YAC-1 lymphoma resulted in reduced sensitivity to in vitro lysis by syngeneic murine spleen cells cultured in rIL-2 (LAK-cells). IFN-gamma treatment also rendered the murine B16 melanoma less sensitive to lysis by syngeneic LAK cells, whereas in vivo passage did not alter LAK sensitivity. The reduction in sensitivity to lysis correlated with enhanced expression of cell surface H-2 on the target cells. The possible role of H-2 was studied with a beta 2-microglobulin-deficient, and thus H-2-deficient, variant of the YAC-1 lymphoma. This variant line remained H-2 negative even after IFN-gamma treatment or in vivo passage, and was highly sensitive to LAK-cell-mediated lysis, even after IFN-gamma treatment or in vivo passage. The present results are discussed in relation to IFN-gamma and in vivo induced modulation of MHC class-1 molecules on target cells and the possible consequences for interaction with activated as well as "natural" effector cells.

Animals↗