Biomedical subjects

H G Ljunggren

Publications and source records attributed to H G Ljunggren.

124 records · Page 7Linked to original sources

PubMed1989

NK sensitivity and lung clearance of MHC-class-I-deficient cells within a heterogeneous fibrosarcoma.

The present study examines clonal variations in NK sensitivity in a methylcholanthrene-induced fibrosarcoma. Previous studies of clones from this tumor have shown considerable heterogeneity in H-2 expression, and an association between deleted or low levels of class-I products and increased tumorigenicity after subcutaneous implantation in immunocompetent syngeneic mice. Here, fibrosarcoma clones with no or low expression of MHC-class-I products were found to be sensitive to NK-mediated lysis, while clones with high levels of MHC-class-I expression were relatively resistant. One H-2+ (G2) and one H-2- (B9) clone were chosen for more detailed studies. Cold-target competition assays and conjugate cytotoxicity assays in agarose showed that splenic effector cells bound equally well to the H-2+ and H-2- tumor clone, although only the latter was sensitive to NK cell lysis. Treatment with 50 U/ml of rIFN-gamma for 48 hr increased the levels of H-2 expression and made both clones more resistant to NK-mediated lysis. In vivo studies with radiolabelled tumor cells showed that cells from the H-2+ clone survived better than cells from the H-2- clone in the pulmonary capillary bed after i.v. inoculation. This difference disappeared in mice treated with anti-asialo GM1 serum, known to deplete NK cell activity.

Animals↗

PubMed1989

Association of class I major histocompatibility heavy and light chains induced by viral peptides.

We describe a cell in which association of a major histocompatibility complex class I heavy chain with beta 2-microglobulin is induced by a peptide derived from influenza nucleoprotein. Association of antigenic peptides with the binding site of class I molecules may be required for correct folding of the heavy chain, association with beta 2-microglobulin and transport of the antigen-MHC complex to the cell surface.

Animals↗

PubMed1989

Studies of sublines selected for loss of HLA expression from an EBV-transformed lymphoblastoid cell line. Changes in sensitivity to cytotoxic T cells activated by allostimulation and natural killer cells activated by IFN or IL-2.

Murine tumor studies have suggested that variations in MHC class I expression may influence the behavior of tumor cells in vivo. Corresponding human tumor studies remain at the descriptive level but they show differences in MHC Ag expression between and even within tumors. Our purpose was to explore possible functional relationships between class I expression and sensitivity to different forms of cell-mediated lysis in a potentially immunogenic system: EBV-immortalized B cells. Their cytotoxic sensitivity was tested to CTL and to IFN- or IL-2-activated effector cells. The wild-type line (high class I) was sensitive to CTL with the appropriate Ag restriction, but resisted lysis by normal or IFN-activated PBL. In contrast, HLA loss variants showed a reduced sensitivity to CTL and an increased NK sensitivity. The latter could be related to the loss of class I molecules: an intermediate (haplotype loss) expressor variant was moderately NK sensitive, whereas a weak expressor line, with an additional down-regulation of the remaining haplotype, was highly sensitive. IL-2-activated PBL ("LAK") cells showed the same killing pattern as NK cells, although the levels of lysis were generally higher. These data support the hypothesis that the MHC class I Ag expression-dependent, CTL-mediated lysis is complemented by additional mechanisms, mediated by effectors that recognize cells with reduced MHC Ag expression that would otherwise escape CTL-mediated rejection.

Cell Line↗

PubMed1989

Molecular analysis of H-2-deficient lymphoma lines. Distinct defects in biosynthesis and association of MHC class I heavy chains and beta 2-microglobulin observed in cells with increased sensitivity to NK cell lysis.

It has previously been reported that MHC class I-deficient RBL-5 and YAC-1 lymphoma sublines show an enhanced NK sensitivity in vitro. In the present study such lymphoma variants were found to have different defects in H-2 biosynthesis such as 1) reduced beta 2-microglobulin and H-2 H chain transcription, 2) block in beta 2-microglobulin translation, and 3) impaired association between beta 2-microglobulin and H-2 H chains. For lines with the latter two defects, the results suggested that a major part of the H chains were arrested before the middle Golgi complex as indicated by their failure to undergo carbohydrate side chain trimming. The data suggest that NK sensitivity can be directly influenced by the membrane expression of MHC class I gene products of tumor targets because three independent molecular defects, all interfering with the cell surface H-2 expression, gave rise to NK-sensitive phenotypes. These variant lines will also be useful tools for studies of H-2 glycoprotein assembly and transport and for Ag presentation to CTL.

Animals↗

PubMed1989

Enhanced H-2 expression and T-cell-dependent rejection after intracerebral transplantation of the murine lymphoma YAC-1.

The relationship between MHC class I (H-2) expression and tumorigenicity was investigated after intracerebral inoculation of the murine lymphoma YAC-1 and its H-2 negative variant, A.H-2-. YAC-1 was less tumorigenic than A.H-2- in normal as well as NK-depleted syngeneic A/Sn mice. However, in T-cell-depleted syngeneic mice YAC-1 was as tumorigenic as A.H-2-. Following intracerebral growth, the H-2 expression of YAC-1 was markedly enhanced in a similar fashion as after intraperitoneal passage. The A.H-2- variant remained H-2 negative after intracranial passage. The H-2 negative variant cells were not rejected from the brain even when intermixed with wild-type YAC-1 cells prior to intracerebral inoculation, excluding an "innocent bystander" effect. In vitro, the intracerebrally passaged YAC-1 line showed enhanced sensitivity to lysis by H-2 Kk Dd (H-2a) specific CTLs but decreased sensitivity to NK cells. The A.H-2- line was unchanged. Our data suggest that the lack of H-2 molecules may facilitate the growth of antigenic tumor cells in the brain due to escape from T-cell-mediated immunosurveillance. Our data also suggest, in line with other recent findings, that intracerebrally growing tumor cells are sheltered from NK cell-mediated rejection.

Animals↗

PubMed1989

A mutant cell in which association of class I heavy and light chains is induced by viral peptides.

Association of the Db heavy chain with beta 2-microglobulin and expression of Db and Kb at the surface of the cell are induced by specific peptides in the mutant RMA-S. Association of antigenic peptides with the binding site of class I molecules may be required for correct folding of the heavy chain, association with beta 2-microglobulin, and transport of the antigen-MHC complex to the cell surface.

Amino Acid Sequence↗

PubMed1989

[Molecular analysis of mouse major histocompatibility complex class I gene expression of tumors growing in the brain].

The authors have investigated the regulation of mouse major histocompatibility complex (MHC, H-2) class I gene expression of tumors growing in the brain, by using T-cell lymphoma (Moloney leukemia virus-induced YAC-1 of A/Sn mouse origin) and its cell surface H-2 negative variants, A. H-2- and beta 2m-. FACS analysis showed that low H-2 expressing YAC-1 markedly increased H-2 Kk, Dd and beta-2 microglobulin (beta 2m) induction on the cell surface after intracerebral (i.c.) passage, while there was no change in phenotypical expression of both A. H-2- and beta 2m-. Southern and Northern blot analyses revealed that the enhancement of H-2 class I expression in YAC-1 was due to transcriptional control of H-2 DNA genes. beta 2m- was confirmed to lack beta 2m- gene, causing cell surface H-2 negative expression. Immunoprecipitation method showed that, despite increase in mRNA of the H-2 gene, A. H-2- disclosed no class I H-2 expression because of the incapability of intracellular association of polypeptides between H-2 and beta 2m in the post-translational level. The H-2 class I expression on YAC-1 cells could also be induced by interferon gamma (IFN) in a dose-dependent manner in the range of 1 to 100 U/ml. At 100 U/ml, the H-2 inducing effect, regulated at the transcriptional level, was comparable to that observed after i.c. passage. In contrast, the A. H-2- and beta 2m- remained completely negative after IFN treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

[Experimental analysis of intracerebral natural resistance against H-2+ and H-2- lymphomas grafted into the brain].

The authors have investigated intracerebral natural resistance mechanism after tumor transplantation into the brain, by using YAC-1 (Moloney leukemia virus-induced T cell lymphoma of A/Sn mouse origin) and its H-2 negative A. H-2-. It was found that highly immunogenic H-2+ YAC-1 was less tumorigenic than A. H-2- in untreated as well as NK-depleted syngeneic mice. The variant cells were not rejected even if inoculated together with YAC-1 cells into the brain. Furthermore, in T cell-depleted, thymectomized mice YAC-1 was as tumorigenic as A. H-2-. Thus, intracerebral natural resistance was expressed against YAC-1, suggesting that T cells but not NK cells might be involved in the tumor rejection with an MHC-restricted regulation. Contrary to this, A. H-2- cells escaped from the natural resistance of the brain. In vitro cytotoxicity assays showed that in relation to the enhancement of cell surface H-2 antigens, intracerebrally passaged YAC-1 cells decreased and increased the sensitivity to NK- and CTL-mediated lysis, respectively. In contrast, A. H-2- did not alter either susceptibility to cell-mediated lysis or cell surface H-2 expression. In vivo rapid elimination assays revealed that after intravenous or subcutaneous inoculation there was a more efficient abrogation of 125I-iododeoxyuridine (IUdR) labelled YAC-1 cells in normal untreated mice compared to NK-depleted mice. After intracerebral inoculation, however, no difference in remaining radioactivity was observed between untreated and NK-depleted mice. This indicates that selective NK-mediated elimination of tumor cells might occur after intravenous or subcutaneous but not after intracerebral inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Natural resistance against lymphoma grafts conveyed by H-2Dd transgene to C57BL mice.

The H-2Dd transgenic strain D8 on C57BL background was more resistant to subcutaneous challenge of RBL-5 lymphoma cells than B6 controls. The direct role of the H-2Dd antigen was investigated by the use of (D8 x B6)F1 crosses and (D8 B6) x B6 backcrosses. The latter showed cosegregation with regard to Dd antigen expression and lymphoma resistance, both of which were inherited in a pattern consistent with control by a single dominant gene. The rejection potential in (D8 x B6)F1 mice appeared as strong as that seen in crosses between B6 and MHC congenic mice (on B10 background) carrying H-2Dd. The lymphoma resistance could be abrogated by treatment with anti-asialo GM1 antiserum or anti-NK 1.1 mAb, indicating a role for NK cells.

Animals↗

PubMed1988

Effects of dimethyl sulfoxide treatment on H-2 expression and susceptibility to NK- or cytotoxic T-lymphocyte-mediated lysis of the YAC-1 lymphoma and its beta 2-microglobulin-deficient variant.

The effects of dimethyl sulfoxide (DMSO) on H-2 expression and susceptibility to NK- and cytotoxic T-lymphocyte (CTL)-mediated lysis in the murine T-cell lymphoma YAC-1 and its beta-2-microglobulin (beta 2m)-deficient variant were studied. Fluorescence-activated cell sorter analysis revealed induction of H-2Kk and beta 2m 3 days after culture of YAC-1 with DMSO, whereas optimal H-2Dd induction required more than 1 week. H-2Kk and H-2Dd induction by DMSO was equal to pretreatment of YAC-1 cells with 50-100 and 10-20 U/ml interferon (IFN)-gamma, respectively, but the T-cell differentiation antigens Lyt-1, Lyt-2, Thy-1, and L3T4 remained unaffected. DMSO protected YAC-1 cells from NK lysis as efficiently as 10-20 U IFN/ml, whereas susceptibility to anti-H-2a-, H-2Kk-, and H-2Dd-specific CTLs was augmented as in IFN-treated YAC-1 cells. In contrast, the beta 2m-deficient variant, which remained H-2 negative at the cell surface after DMSO treatment, also remained NK sensitive. Thus DMSO can induce H-2 expression and alter the sensitivity of murine lymphoma cells to different effector cells.

Animals↗

PubMed1988

Selective acceptance of MHC class I-deficient tumor grafts in the brain.

H-2-deficient (H-2-) tumor variants were accepted equally well compared with H-2+ wild-type cells in the brain of syngeneic mice, while the H-2- cells were selectively eliminated when inoculated extracranially. This indicates a specific absence or suppression of the defense against MHC class I-deficient cells in the brain, suggested to be mediated by NK cells. In contrast, T cell-mediated immune reactions could clearly be detected in the brain under the same experimental conditions. This was shown in control experiments where H-2+ tumor cells were rejected from the brain of preimmunized or allogeneic mice. The present findings may be important for the understanding of neurotropic virus infections, immunology and immunotherapy of brain tumors, as well as for the growing interest in tissue grafting within the central nervous system.

Animals↗

PubMed1988

Afferent and efferent cellular interactions in natural resistance directed against MHC class I deficient tumor grafts.

H-2-deficient variants, selected from the murine lymphoma RBL-5, were recently shown to be less tumorigenic in syngeneic mice compared with the corresponding H-2-positive wild-type cell line. The present study focused on the detailed cellular interactions leading to the specific rejection of H-2-deficient cells in vivo. In vivo experiments with mixed tumor inocula, measuring either tumor outgrowth or rapid elimination, showed that the presence of H-2-positive lymphoma cells did not suppress the rejection of H-2-deficient cells. Conversely, H-2-deficient cells did not activate a rejection of H-2-positive cells. H-2-deficient cells were selectively eliminated even when they were present in a 10-fold excess compared with the H-2-positive lymphoma cells in the same inoculum. In vitro, H-2-deficient cells were more sensitive to killing by spleen cells from mice treated with interferon or natural killer-inducing agents. The presence of cold H-2-deficient cells did not activate the killing of H-2-positive cells, and H-2-positive cells did not inhibit killing of H-2-deficient cells. Such mixing experiments revealed a more efficient cold target inhibition by the H-2-deficient cells, although no difference was seen between these and the H-2-positive wild-type cells in target binding assays. When Thy-1.2+, nylon wool adherent or phagocytic populations were removed from normal spleen effectors, the difference in spontaneous cell-mediated cytotoxicity between the H-2-deficient and the H-2-positive cells persisted. This result was also obtained when spleen cell effectors from nude mice or asialo GM1+ effectors, positively enriched by fluorescence-activated cell sorter, were used. The results show that the selectivity in the rejection of H-2-deficient cells was not determined in the afferent arm alone. The present data fit with a previously proposed model where natural killer cells would bind equally well to both major histocompatibility complex class I negative and class I positive target cells, but only the latter would be able to present a postbinding inhibitory signal allowing them to escape killing which results in outgrowth in vivo and poor cold target competition in vitro.

Animals↗

PubMed1985

Host resistance directed selectively against H-2-deficient lymphoma variants. Analysis of the mechanism.

Three independent variants with a profound reduction of cell surface H-2 have been selected from the C57BL/6 mouse-derived RBL-5 and EL-4 T lymphomas. After subcutaneous inoculation of low cell doses in syngeneic mice, the H-2- variants failed to grow out, whereas the H-2+ control lines showed progressive growth. No difference in growth rate or cloning efficiency was detectable in tissue culture. The in vivo difference in tumor outgrowth was analyzed in detail for one of the H-2-low lines. The outgrowth difference remained after the H-2-low variant and the control line had been injected subcutaneously in opposite flanks of the same mouse, and it was not dependent upon activity of mature T cells, since the same result was seen in athymic nude mice. The difference was partially sensitive to irradiation of the hosts. When mice were pretreated with anti-asialo GM1 antiserum, known to depress natural killer (NK) cell activity, the difference in outgrowth was abolished, and both the control line and the H-2- variant showed progressive growth in vivo. Experiments comparing the distribution and survival of isotope-prelabeled variant and wild type cells indicated that a rapid elimination of the former took place within 24 h after intravenous injection. These differences in tumor elimination were not seen in mice treated with anti-asialo GM1 antiserum. We conclude that the reduced tumorigenicity of sublines with impaired H-2 expression is largely, if not exclusively due to rapid elimination by NK cells. These findings may reflect an inverse, indirect relation between factors controlling H-2 expression and NK sensitivity. Another possible explanation is that major histocompatibility complex (MHC)-encoded gene products are directly involved in a regulatory signal in the NK cell system. According to this interpretation, immunological selectivity in the NK cell system would be achieved by the failure to recognize self-MHC, irrespective of the presence of foreign antigens, i.e. by detection of no-self rather than of nonself. This may also explain previous observations on H-2-linked hybrid resistance against lymphoid grafts and changes in H-2 phenotypes associated with tumor progression.

Animals↗

PubMed1985

YAC-1 MHC class I variants reveal an association between decreased NK sensitivity and increased H-2 expression after interferon treatment or in vivo passage.

Two H-2 negative variants of the YAC-1 lymphoma were selected by mutagenization and sequential in vitro selections and compared with wild-type cells for changes in NK sensitivity and H-2 expression after interferon treatment or in vivo passage. The H-2 negative variants and the low H-2 expressor YAC-1 wild-type cells had similar NK sensitivity. However, IFN-beta or recombinant IFN-gamma pretreatments increased the H-2 expression of YAC-1 and protected them from NK lysis, whereas the H-2 variants, which remained H-2 negative, were not protected and often more sensitive to NK lysis. The H-2 variants were similarly susceptible as wild-type cells to three other cellular effects of interferon: protection from virus infection, modulation of Con A capping, and inhibition of cell proliferation. Thus, the only interferon-mediated effect that distinguished the H-2 negative variants from wild-type cells was the inability of the former to increase their H-2 expression and decrease their NK sensitivity. The wild-type YAC-1 line showed increased H-2 expression and decreased NK sensitivity after in vivo passage. In contrast, in vivo passaged H-2 variants showed no reexpression of H-2, and remained NK sensitive. The altered responses to interferon and in vivo passage were specific for loss or down-regulation of H-2, because Thy-1 loss (H-2 positive) YAC-1 variants behaved as the wild-type cells in all respects. This study supports the hypothesis that NK cells may function in vivo to eliminate host cells that fail to express H-2 after interferon stimulation during an immune response; such cells are a potential threat because they may escape recognition by T lymphocytes despite the expression of viral or tumor-associated antigens.

Animals↗

PubMedDate not supplied

Selective rejection of H-2-deficient lymphoma variants suggests alternative immune defence strategy.

Metazoan organisms may discriminate between self and non-self not only by the presence of foreign antigens but also by the absence of normal self markers. Mammalian adaptive immune responses use the first strategy, with the additional requirement that foreign antigens are recognized in the context of self-major histocompatibility complex (MHC) products at the cell surface. Aberrant cells which fail to express MHC products adequately can therefore avoid detection. A more primitive but complementary defence system, eliminating such cells on the basis of absent self-markers, is suggested by a re-interpretation of phenomena associated with metastasis and natural resistance. We now show that murine lymphoma cells selected for loss of H-2 expression are less malignant after low-dose inoculation in syngeneic hosts than are wild-type cells, and that the rejection of such cells is non-adaptive. On the basis of our data, we suggest that natural killer cells are effector cells in a defence system geared to detect the deleted or reduced expression of self-MHC.

Animals↗

PubMedDate not supplied

Experimental strategies and interpretations in the analysis of changes in MHC gene expression during tumour progression. Opposing influences of T cell and natural killer mediated resistance?

The RBL-5 lymphoma has previously been shown to be highly sensitive to natural hybrid resistance, under the control of H-2 genes at the host level. The present study of the RBL-5 tumour was focused on progression towards disseminated growth after intravenous (i.v.) inoculation in the syngeneic host and the possible influence of the MHC genes at the tumour cell level. Data are presented to illustrate that there is no obligatory association between reduced H-2 expression and increased malignancy, and that the opposite may be observed. The wild type RBL-5 line expressed readily detectable H-2K and H-2D products, and a highly malignant subline selected for lung colonization in vivo did not show any reduction but rather enhanced expression of these antigens. Depending on the inoculum size, this selected subline caused disseminated lymphoma (in the liver, spleen and lungs) at a faster rate or higher frequency of animals than the wild type line. Conversely, a subline selected for reduced H-2 expression in vitro, by repeated treatments with antibody and complement, failed to form colonies in any organ after i.v. inoculation, even if the cell dose was increased by more than 100-fold in comparison with the threshold dose for the wild type line. This H-2-deficient subline was completely resistant to syngeneic RBL-5 immune cytotoxic T lymphocytes (CTL). Clones isolated during selection of the subline showed different degrees of reduction in sensitivity to H-2 specific CTL, but an inverse pattern of sensitivity to poly I:C induced natural killer (NK) cells. Selection pressure imposed by NK-mediated elimination directed preferentially against cells with reduced H-2 expression may be one explanation of why the gain of histocompatibility antigens is associated with tumour progression in some systems. Another important implication taken up for discussion is that tests for the effect of MHC modulation on tumour growth or immunotherapy require careful experimental design, to cover the action of different effector mechanisms in vivo.

Animals↗