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A M Krieg

Publications and source records attributed to A M Krieg.

At least 127 records · Page 7Linked to original sources
PubMed1992

Heterogeneous expression and coordinate regulation of endogenous retroviral sequences in human peripheral blood mononuclear cells.

This study examines the expression of human endogenous retroviral or retroviral-like (ERV) sequences in peripheral blood mononuclear cells (PBMC). Probes to 12 human ERV were used in Northern analyses of 38 patients with autoimmune muscle diseases and 31 blood donor controls. All patients and controls expressed multiple classes of ERV RNA. This expression was quite heterogenous: for each of the nine ERV classes for which expression was detected, some individuals showed high RNA levels whereas others showed low levels. ERV expression was independent of disease and autoantibody production. Statistical analysis of densitometric data indicated that expression of several classes of ERV was coordinately regulated. ERV expression in individual patients showed coordinate fluctuations with time. These studies demonstrate the heterogeneity and coordinate regulation of human ERV expression. To evaluate whether ERV expression might be affected by lymphocyte activation, PBMC were cultured with or without lymphocyte mitogens before RNA extraction. These studies demonstrated complex changes in ERV expression after lymphocyte activation. Murine ERV have several immunoregulatory activities. If human ERV have analogous effects, their heterogeneous expression and association with lymphocyte activation may have important biologic consequences.

Autoimmune Diseases↗
PubMed1992

Nonspecific suppression of [3H]thymidine incorporation by "control" oligonucleotides.

Phosphodiester oligonucleotides are rapidly degraded in spleen cell cultures. The present studies were conducted to determine whether thymidine released from degradation of such oligonucleotides could be reutilized and compete with [3H]thymidine incorporation, thereby causing nonspecific inhibition of "proliferation" assays. Our studies in mitogen-stimulated mouse spleen cells demonstrate that "control" oligonucleotides that contain thymidine can cause more than 90% inhibition of [3H]thymidine incorporation. This inhibitory effect was generally dependent on the location of the thymidine within the oligonucleotide: oligonucleotides that had 3'-terminal thymidine(s) caused more suppression than those in which thymidines were at the 5' end. All oligonucleotides caused a modest but variable inhibition of [3H]uridine incorporation. Furthermore, [3H]thymidine incorporation was partially inhibited even by oligonucleotides that did not contain thymidine. We propose that investigators who use [3H]thymidine incorporation assays to assess antisense effects do so with caution. It may be prudent to use control oligonucleotides with the same number and location of thymidine bases and to confirm [3H]thymidine incorporation assays with other measures of cell proliferation.

Animals↗
PubMed1992

Molecular aspects of systemic lupus erythematosus: murine endogenous retroviral expression.

Systemic lupus erythematosus is an immune-mediated disease in which the etiology is unknown. Full-length (8.4 kb), type C, modified polytropic (Mpmv) retroviral transcripts from the thymus are characteristic of murine lupus. Reciprocal bone marrow transplantation studies determined that this thymic expression maps to the pre-T bone marrow stem cell. In vitro and in vivo oligonucleotide antisense work suggest that type C retroviruses play a role in immune activation. This paper summarizes our studies of endogenous retroviruses in murine lupus.

Animals↗
PubMed1992

Endogenous retroviruses: potential etiologic agents in autoimmunity.

The genomes of all organisms, from yeast to humans, contain thousands of endogenous retroviruses (ERV). In most species all or almost all ERV are noninfectious, but some ERV retain open reading frames capable of encoding proteins. RNA and proteins derived from ERV are expressed in humans and other species. Until recently, there was little evidence that this ERV expression resulted in any immunologic effects. Recent studies make it increasingly clear that some ERV have important immunologic effects. The immune effects of ERV expression raise the question of a possible pathogenic role in idiopathic autoimmune diseases. Interest in this question has been heightened by the observation that some infectious retroviruses cause manifestations of autoimmunity. Nonetheless, attempts to isolate infectious retroviruses from patients with idiopathic autoimmune diseases have generally failed. The possible role of ERV in idiopathic autoimmune diseases has not yet been fully explored. This review focuses on the known and the potential immune effects of ERV, especially as they may relate to autoimmune diseases.

Animals↗
PubMed1991

NIH conference. Systemic lupus erythematosus.

Although the cause of systemic lupus erythematosus remains unknown, pathogenic mechanisms are becoming clearer. Both genetic and environmental factors have been implicated in the induction and in the perpetuation of lupus. Implicated environmental triggers include ultraviolet light, chemicals (hydrazines, hair dyes, drugs), some foods, and possibly infectious agents. Lupus is mediated by the immune system. Patients have excess numbers of antibody-forming cells, including those that produce antibodies reactive with self-antigens. Patients also have an increased number of activated T cells, some of which help B cells to produce autoantibodies. A loss of tolerance is a critical immune abnormality in lupus; many of the activated helper T cells may result from a failure in normal tolerance mechanisms. A hematopoietic stem-cell defect could give rise to both B- and T-cell abnormalities. Such a stem-cell abnormality might lead to both a loss of self-tolerance and polyclonal B-cell activation. Antigen-driven, T-cell-dependent expansion of B-cell clones would then give rise to pathogenic autoantibodies, including anti-DNA. We believe that lupus is a syndrome: Patients differ regarding specific inciting factors and immune defects. Some patients have genetically conditioned abnormalities, similar to those found in mice with lupus; others have a combination of genetic and acquired defects. We hope that insights into pathogenesis lead to improved and more individualized therapy.

Animals↗
PubMed1991

Association of murine lupus and thymic full-length endogenous retroviral expression maps to a bone marrow stem cell.

Recent studies of thymic gene expression in murine lupus have demonstrated 8.4-kb (full-length size) modified polytropic (Mpmv) endogenous retroviral RNA. In contrast, normal control mouse strains do not produce detectable amounts of such RNA in their thymuses. Prior studies have attributed a defect in experimental tolerance in murine lupus to a bone marrow stem cell rather than to the thymic epithelium; in contrast, infectious retroviral expression has been associated with the thymic epithelium, rather than with the bone marrow stem cell. The present study was designed to determine whether the abnormal Mpmv expression associated with murine lupus mapped to thymic epithelium or to a marrow precursor. Lethally irradiated control and lupus-prone mice were reconstituted with T cell depleted bone marrow; one month later their thymuses were studied for endogenous retroviral RNA and protein expression. Recipients of bone marrow from nonautoimmune donors expressed neither 8.4-kb Mpmv RNA nor surface MCF gp70 in their thymuses. In contrast, recipients of bone marrow from autoimmune NZB or BXSB donors expressed thymic 8.4-kb Mpmv RNA and mink cell focus-forming gp70. These studies demonstrate that lupus-associated 8.4-kb Mpmv endogenous retroviral expression is determined by bone marrow stem cells.

Animals↗
PubMed1991

Uptake of oligodeoxyribonucleotides by lymphoid cells is heterogeneous and inducible.

Oligonucleotide uptake was studied in cultured murine spleen and lymph node cells using internally radiolabeled and fluorescein-5-isothiocyanate (FITC)-labeled oligonucleotides. Lymphoid subpopulations were distinguished by flow cytometry and staining with antibodies to cell-surface molecules. Approximately 5% of fresh lymphoid cells take up substantial amounts of oligonucleotide. The percentage of B cells that take up oligonucleotide increased fivefold if cells were cultured for at least 24 hr prior to incubation with labeled oligonucleotides, and increased 10-fold if cells were precultured for 48 hr. T-cell uptake changed very little in culture. Cultured CD4+ and CD8+ T cells had similar oligonucleotide uptake that was less than one-third of that in cultured B cells, but CD4-CD8- T cells had a higher percentage of cells taking up oligonucleotide than did B cells. T- or B-cell mitogens caused markedly increased oligonucleotide uptake in T or B cells, respectively. Oligonucleotide uptake could be inhibited only partially with competitor DNA. To distinguish between cell membrane-bound and intracellular oligonucleotide, cells were washed in acid glycine buffer (which removes most surface oligonucleotide). This demonstrated that most of the oligonucleotide was intracellular. We conclude that oligonucleotide uptake is quite heterogeneous among cultured cells, and that this uptake is inducible by mitogens. These data may be important for the design and interpretation of in vitro experiments, and for the planning of in vivo therapy with antisense oligonucleotides.

Animals↗
PubMed1990

Preferential nuclear compartmentalization of endogenous mink cell focus-forming-related retroviral transcripts.

Endogenous mink cell focus-forming (MCF)-like retroviral sequences in the murine genome are stable, inherited sequences analogous to other chromosomal genes. As such, it is thought that they are transcribed and translated in a manner analogous to other genes. However, when the SL12.4 CD4-, CD8- thymoma cell line was studied for nuclear/cytoplasmic distribution of endogenous MCF-related transcripts, there was a nuclear predominance. The great majority of full-length 8.4-kb endogenous MCF-related transcripts were nuclear. Even the smaller, spliced 3.0-kb transcripts were at least as prominent in the nucleus as the cytoplasm, whereas cellular RNA was 80% cytoplasmic and other cellular transcripts were represented in the cytoplasm to a much greater extent than the nucleus. Size cannot fully account for the nuclear presence of MCF-related endogenous transcripts, because the 3.0-kb MCF transcripts occurred in the nucleus to a much greater relative extent than 3.8-kb c-myb transcripts. These studies point to retroviral-like structures of these transcripts as influencing their intracellular compartmentalization.

Animals↗
PubMed1990

Analysis of thymic endogenous retroviral expression in murine lupus. Genetic and immune studies.

Inbred mouse genomes contain two subclasses of proviruses related to mink cell focus-forming (MCF) retroviruses: polytropic (Pmv), and modified polytropic (Mpmv). To determine whether one of these subclasses is associated with murine lupus, oligonucleotide probes specific for Pmv or Mpmv sequences were used in Northern analyses. Thymus 8.4 kb Mpmv RNA was expressed in five of five lupus-prone strains and crosses and this expression was not affected by genes that retard or accelerate development of lupus. Two of four leukemia-prone strains expressed low levels of such thymic transcripts, but none of 11 control strains did. 8.4 kb Mpmv RNA expression was not induced in thymuses of control mice by the lpr/lpr or gld/gld genotypes (which cause polyclonal immune activation) nor by treatment with mitogens. In contrast to Mpmv, thymic 8.4 kb Pmv expression was poorly associated with autoimmunity: it was easily detected in nearly all strains, and was increased by polyclonal activation in control mice. These studies indicate that the organ-specific thymic 8.4 kb Mpmv expression (a) is characteristic of several genetic backgrounds which predispose to murine lupus, (b) precedes and does not correlate with disease development, (c) is not due to polyclonal activation, and (d) is regulated independently of 8.4 kb Pmv expression.

Animals↗
PubMed1989

A role for endogenous retroviral sequences in the regulation of lymphocyte activation.

The genomes of most vertebrates contain numerous retroviral sequences, the great majority of which are non-infectious. These endogenous retroviral sequences are transcribed and translated in many host tissues, and are induced by mitogens. The function, if any, of endogenous retroviruses has been unclear. The transmembrane envelope proteins of some infectious type C retroviruses suppress lymphocyte activation, but it is unknown whether any endogenous type C retroviruses share this suppressive activity. To study the possible effects of murine endogenous retroviral expression, specific antisense oligonucleotides were synthesized complementary to type C retroviral sequences, and were cultured with murine spleen cells. If any of these endogenous retroviruses are suppressing lymphocyte activation, then inhibiting such endogenous retroviral-mediated suppression with antisense might result in lymphocyte stimulation. Three classes of endogenous type C retroviral sequences may be distinguished by antisense oligonucleotides (based on their homology to infectious retroviruses): ecotropic, xenotropic, and mink cell focus-forming (MCF). Antisense oligonucleotides to endogenous MCF envelope gene (env) initiation regions caused: i) doubling or tripling of spleen cell RNA synthesis, and ii) marked increases in lymphocyte surface Ia and Ig expression relative to control oligonucleotides. Antisense oligos to xenotropic or ecotropic env sequences or to endogenous MCF non-envelope sequences had no effect. These data suggest that endogenous MCF sequences exert an inhibitory influence on the murine immune system. Because endogenous MCF expression is inducible by immune stimuli, such expression could constitute an inhibitory feedback circuit that participates in the regulation of immune homeostasis.

Animals↗
PubMed1989

Expression of an endogenous retroviral transcript is associated with murine lupus.

We have been investigating whether murine lupus is associated with endogenous type C retroviral expression. We used Northern blot analyses and oligonucleotide probes, which are able to distinguish the envelope genes of the xenotropic and mink cell focus-forming (MCF) classes of type C retroviruses. Xenotropic expression in the spleen varied markedly among inbred mouse strains; although all strains expressed a 1.8-kb transcript, only one-half expressed one or more larger transcripts (8.4, 7.2, and/or 3.0 kb). Autoimmune disease did not correlate with expression of any of the xenotropic transcripts. Xenotropic and MCF transcripts were expressed independently among the mouse strains studied. Splenic RNA from all strains contained 7.2-, 3.0-, and 1.8-kb MCF transcripts. Some strains also expressed 8.4-kb MCF splenic RNA. There was a strong association between murine lupus and expression of 8.4-kb MCF transcripts: 6 of 6 lupus-prone strains, but only 2 of 11 nonautoimmune strains, had detectable 8.4-kb MCF RNA. The xid and Yaa mutations had minimal effects on expression of 8.4-kb MCF-related transcripts, despite their major and opposite effects on disease. Moreover, New Zealand black mice highly expressed this RNA from day 1 of life, before disease development. The data suggest that expression of 8.4-kb MCF endogenous retroviral transcripts is a primary feature of murine lupus and is not secondary to disease expression.

Animals↗
PubMed1989

Negative control region at the 5' end of murine leukemia virus long terminal repeats.

Using in vitro protein binding and in vivo functional studies, we have identified novel regulatory sequences near the 5' end of murine leukemia virus (MuLV) long terminal repeats (LTRs). These sequences are highly conserved in all MuLV LTRs as well as in feline leukemia virus and gibbon ape leukemia virus LTRs. In this upstream conserved region (UCR), gel retardation assays detected two overlapping but distinct binding sites (UCR-U and UCR-L) for nuclear proteins (UCRF-U and UCRF-L). Three lines of evidence suggest a negative regulatory role for the UCR in viral transcription: (i) an inverse correlation was found between MuLV transcripts and nuclear proteins binding the UCR in the spleens of five different mouse strains; (ii) in vivo treatment of NFS mice with lipopolysaccharide resulted in the induction of splenic viral transcripts and the concomitant disappearance of UCR-binding proteins; and (iii) in mouse L cells transfected with an MuLV LTR linked to the chloramphenicol acetyltransferase (CAT) gene, cotransfected UCR oligonucleotides increased CAT expression, presumably by competing for inhibitory trans-acting factors.

Animals↗
PubMed1988

Multiple endogenous xenotropic and mink cell focus-forming murine leukemia virus-related transcripts are induced by polyclonal immune activators.

Northern (RNA) analyses were used to study the kinetics of induction of endogenous mink cell focus-forming (MCF) and xenotropic murine leukemia virus (MuLV)-related sequences in NFS and C57BL/6 mice injected with the polyclonal immune activators lipopolysaccharide (LPS), concanavalin A, and 8-bromoguanosine. All three mitogens induced 8.4-, 7.2-, 3.0-, and 1.8-kilobase (kb) MCF-related transcripts coordinately in the spleens of injected mice. Xenotropic MuLV-related expression was also rapidly induced in spleens by the three polyclonal immune activators, but in a noncoordinate manner: a distinct set of transcripts with different kinetics of expression was induced by each mitogen. MCF-related induction after LPS injection was both rapid and sustained; it began within 30 min and persisted for at least 8 days in the spleens of both NFS and C57BL/6 mice. LPS also caused prolonged induction of xenotropic transcripts in spleens of C57BL/6 but not NFS mice. The gld mutation, which causes polyclonal immune activation, induced 8.4-, 10.0-, and 13-kb MCF-related transcripts in C3H/HeJ mice without altering expression of 7.2-, 5.6-, 4.0-, 3.0-, or 1.8-kb MCF-related transcripts. The data demonstrate that individual endogenous MuLV-related transcripts can be induced coordinately or independently and suggest that expression of these transcripts is linked to early stages of lymphocyte activation.

Adjuvants, Immunologic↗
PubMed1988

NIH conference. Angioimmunoblastic lymphadenopathy with dysproteinemia.

Angioimmunoblastic lymphadenopathy with dysproteinemia is a disorder characterized by a sudden onset of constitutional symptoms and lymphadenopathy. Patients often have hypergammaglobulinemia, autoantibodies, rashes, thrombocytopenia, or hemolytic anemia. Diagnosis requires a lymph node biopsy that shows architectural effacement, absence of germinal centers, arborization of postcapillary venules, and a polymorphous infiltrate that includes immunoblasts. Early in the disease, activated T cells in blood and lymph nodes stimulate B cells to proliferate and produce antibody. However, late in the disease, immune suppression may result from increased suppressor function. Clonal rearrangements, which are seen in all patients with regard to either the T-cell receptor beta-chain gene or immunoglobulin genes, have been followed by malignant transformation and frank lymphoma in some patients. Thus, this disorder stands partway between benign lymphoid proliferation and clonal lymphoid transformation. The prognosis of this disorder is poor; 75% of patients die within 2 years or develop a lymphoid malignancy. The rest usually go into a sustained remission. Current treatment with corticosteroid and immunosuppressive agents is unsatisfactory, especially because of late immunosuppression and predisposition to infections.

Blood Protein Disorders↗