HLA class II induction in human islet cells by interferon-gamma plus tumour necrosis factor or lymphotoxin

Two distinct nuclear factors bind the conserved regulatory sequences of a rabbit major histocompatibility complex class II gene

The constitutive coexpression of the major histocompatibility complex (MHC) class II genes in B lymphocytes requires positive, trans-acting transcriptional factors. The need for these trans-acting factors has been suggested by the reversion of the MHC class II-negative phenotype of rare B-lymphocyte mutants through somatic cell fusion with B cells or T-cell lines. The mechanism by which the trans-acting factors exert their effect on gene transcription is unknown. The possibility that two highly conserved DNA sequences, located 90 to 100 base pairs (bp) (the A sequence) and 60 to 70 bp (the B sequence) upstream of the transcription start site of the class II genes, are recognized by the trans-acting factors was investigated in this study. By using the gel electrophoresis retardation assay, a minimum of two proteins which specifically bound the conserved A or B sequence of a rabbit DP beta gene were identified in murine nuclear extracts of a B-lymphoma cell line, A20-2J. Fractionation of nuclear extract through a heparin-agarose column allowed the identification of one protein, designated NF-MHCIIB, which bound an oligonucleotide containing the B sequence and protected the entire B sequence in the DNase I protection analysis. Another protein, designated NF-MHCIIA, which bound an oligonucleotide containing the A sequence and partially protected the 3' half of this sequence, was also identified. NF-MHCIIB did not protect a CCAAT sequence located 17 bp downstream of the B sequence. The possible relationship between these DNA-binding factors and the trans-acting factors identified in the cell fusion experiments is discussed.

Methimazole blocks Graves' IgG but not interferon-gamma HLA-DR expression by thyroid cells

We have expanded our early observation that a potent Graves' IgG preparation induces HLA-DR expression on thyroid cells, by showing that four randomly-selected Graves' IgG's were also capable of inducing DR antigens on thyroid cells. The effect of Graves' IgG was specific to thyroid cells, as it did not induce MHC Class II molecule expression on endothelial cells whereas interferon-gamma and immune complexes did so. The anti-thyroid drug methimazole was capable of rapidly reducing Graves' IgG-induced DR expression but to a much lesser extent than brought about by interferon-gamma. We conclude that Graves' IgG propagates thyroid-specific autoaggression by continued induction of DR antigens and than an important means whereby methimazole brings about remission is by reducing this induction.

Differential expression and regulation of major histocompatibility complex (MHC) products in neural and glial cells of the human fetal brain

The cells of the central nervous system (CNS) have the peculiarity of physiologically expressing very low levels of HLA molecules. In multiple sclerosis (MS), however, as in endocrine autoimmune diseases, there is a marked increase of HLA expression in the tissue (i.e. the plaques) and this is attributable not only to infiltrating cells but also to the astrocytes. To gain an insight into the regulation of HLA in the different cell types in the CNS and to compare it to that observed in the endocrine organs, we have studied the effect of the lympho/monokines interferon (IFN)-alpha and -gamma, tumour necrosis factor (TNF)-alpha, and interleukin (IL)-2 and other agents on this aspect of the biology of human fetal brain cells in culture. A two-colour immunofluorescence technique which combines antibodies to diverse CNS cell markers and monoclonal antibodies (MoAbs) to the non-polymorphic region of HLA molecules was used throughout this study. In control cultures, only astrocytes expressed MHC class I, but after incubation with either IFN-gamma or TNF-alpha oligodendrocytes acquired class I expression. Surprisingly, astrocytes became spontaneously class II positive in culture and this was greatly enhanced by IFN-gamma. Other agents such as IL-2, epidermal growth factor, phorbolmyristate acetate and lectins had no effect. The expression of HLA molecules in the cells of the CNS both in basal conditions and in response to lymphokines is therefore selective and highly heterogenous, thus reflecting their intrinsic biological diversity. These findings may help to explain the features of the immunopathology of MS and also of latent viral infections of neural cells.

Interferons and autoimmunity

Autoimmunity can be accelerated in several genetically prone murine models and can even be induced in normal mice by treatment with interferon (IFN) or IFN-inducers. Several cases of IFN-induced autoimmune disease in humans also have been observed; however, more striking is the fact that some of the clinical manifestations in autoimmune diseases and many of the immunological aberrations can be mediated or enhanced by IFN. The finding of high levels of circulating IFN in many patients may be highly significant in that respect, and the characterization of the predominant type of IFN as an unusual acid-labile IFN-alpha may indicate an infectious etiologic agent in autoimmunity, since this peculiar IFN was mostly associated with viral infections in vivo or in vitro. The induction of MHC class II antigens on previously HLA-DR or Ia negative cells appears to be caused primarily by IFN-gamma and may have a central role in the pathogenesis of autoimmunity in susceptible individuals. Such aberrant HLA-DR expression on nonlymphoid cells can be detected early in the disease in the target organs of many varied autoimmune conditions and may trigger a cascade of self-directed, uncontrolled immune response in conjunction with other factors.

Two distinct nuclear factors bind the conserved regulatory sequences of a rabbit major histocompatibility complex class II gene

The constitutive coexpression of the major histocompatibility complex (MHC) class II genes in B lymphocytes requires positive, trans-acting transcriptional factors. The need for these trans-acting factors has been suggested by the reversion of the MHC class II-negative phenotype of rare B-lymphocyte mutants through somatic cell fusion with B cells or T-cell lines. The mechanism by which the trans-acting factors exert their effect on gene transcription is unknown. The possibility that two highly conserved DNA sequences, located 90 to 100 base pairs (bp) (the A sequence) and 60 to 70 bp (the B sequence) upstream of the transcription start site of the class II genes, are recognized by the trans-acting factors was investigated in this study. By using the gel electrophoresis retardation assay, a minimum of two proteins which specifically bound the conserved A or B sequence of a rabbit DP beta gene were identified in murine nuclear extracts of a B-lymphoma cell line, A20-2J. Fractionation of nuclear extract through a heparin-agarose column allowed the identification of one protein, designated NF-MHCIIB, which bound an oligonucleotide containing the B sequence and protected the entire B sequence in the DNase I protection analysis. Another protein, designated NF-MHCIIA, which bound an oligonucleotide containing the A sequence and partially protected the 3' half of this sequence, was also identified. NF-MHCIIB did not protect a CCAAT sequence located 17 bp downstream of the B sequence. The possible relationship between these DNA-binding factors and the trans-acting factors identified in the cell fusion experiments is discussed.

Interferon-gamma in vivo. Induction and loss of class II MHC antigens and immature myelomonocytic cells in rat organs

The effects of recombinant rat interferon-gamma on class II major histocompatibility complex antigen expression in vivo were studied by immunohistology in LEW rats after continuous intravenous infusion for three days. Interferon-gamma administration led to a systemic induction of class II molecules in previously negative parenchymal and stromal cells. The induction patterns observed were highly reproducible, but not closely dose dependent within a 25-fold dose difference tested. However, the effect of interferon infusion differed profoundly in individual cell types, and appeared to be related to the differentiation stage of each cell population. Thus, epithelial cells like duct epithelia, urothelium or basal ear skin keratinocytes as well as endothelia in big vessels were strongly and easily induced for class II antigen expression. Parenchymal cells like cardiomyocytes and hepatocytes showed intermediate reactivity, while capillary endothelia, neurons in the brain, straight proximal kidney tubules or endocrine pancreatic islet cells did not express class II antigens. The induced expression was rapidly lost from most cells within one or two days after interferon withdrawal; the only exception occurred in keratinocytes. Long-term alterations were, however, still found 14 days after infusion. Interstitial class II-positive dendritic-shaped cells were increased in the organs and hepatic Kupffer cells carried class II antigens. On conventional histology all organs appeared perfectly normal at this date. After three days of interferon, cells of an immature myelomonocytic phenotype occluded medium-sized and small veins in all organs and occurred in granuloma-like lesions in the liver. Although these cells quickly disappeared after interferon withdrawal they might have been at least partially responsible for single deaths on day three. Our study provides a basis for testing the immunological in vivo function of parenchymal class II antigen expression and its differentiation-specific regulation.

Diabetes and tolerance in transgenic mice expressing class II MHC molecules in pancreatic beta cells

Insulin-dependent diabetes is caused by the loss of insulin-producing beta cells in pancreatic islets. It has been proposed that aberrant expression of Class II Major Histocompatibility Complex (MHC) molecules on beta cells stimulates an autoimmune attack against beta cell antigens. To test this hypothesis, we generated transgenic mice that express Class II MHC molecules (E alpha d/E beta b, or I-Eb) on beta cells. Diabetes was found in 100% of transgenic progeny from three expressing transgenic mouse lines, but without evidence for lymphocytic infiltrates. Furthermore, T lymphocytes appeared to be tolerant to the transgene I-Eb molecule, despite the absence of expression of I-Eb in the thymus or any other lymphoid tissue. The results suggest that novel expression of Class II MHC molecules on nonlymphoid cells is by itself insufficient to initiate autoimmune responses against tissue-specific antigens.

Insulin-dependent diabetes mellitus induced in transgenic mice by ectopic expression of class II MHC and interferon-gamma

We have produced transgenic mouse strains harboring class II major histocompatibility complex or interferon-gamma genes linked to the human insulin promoter. These experiments were designed to investigate the consequences of the expression of immunological effector molecules by nonimmunological cells. In both of these studies we observed the disappearance from the pancreas of the insulin-producing beta cells coinciding with the development of insulin-dependent diabetes mellitus. Transgenic mice expressing both chains of the I-A gene showed progressive atrophy of the islets of Langerhans, whereas mice expressing interferon-gamma suffered an inflammatory destruction of the islets.

Three distinct classes of regulatory cytokines control endothelial cell MHC antigen expression. Interactions with immune gamma interferon differentiate the effects of tumor necrosis factor and lymphotoxin from those of leukocyte alpha and fibroblast beta interferons

Recombinant preparations of TNF and lymphotoxin (LT) increase the expression of class I MHC antigens on cultured human endothelial cells (EC) without inducing expression of class II antigens. These actions are similar to those of rIFN-alpha or rIFN-beta. However, TNF and LT differ from IFN-alpha/beta in that the former synergize with IFN-gamma for class I regulation whereas the latter do not. Furthermore, LT or TNF do not affect IFN-gamma-mediated class II induction at optimal class I inducing concentrations (100 U/ml), whereas IFN-alpha and IFN-beta (at their optimal concentrations of 1,000 U/ml) are strikingly inhibitory. LT and TNF also can further increase expression of class I antigens on cells already maximally stimulated by IFN-alpha or IFN-beta. A recombinant preparation of IL-6 (formerly called 26-kD protein, IFN-beta 2, or B cell stimulating factor 2) was without effect on class I expression in EC. These data make it seem unlikely that the actions of LT or TNF on EC expression of MHC antigens are mediated through autocrine or paracrine production of IFN-alpha, IFN-beta or IL-6. More importantly, they suggest that LT or TNF are more likely to be immunostimulatory, whereas IFN-alpha or IFN-beta are more likely to be immunoinhibitory in vivo, a consideration of potential relevance for cytokine administration to various patient populations.

Synergy between interferons and monokines in MHC induction on brain endothelium

Rat brain endothelial cells were cultured as confluent monolayers and stimulated with combinations of interferon-beta (IFN beta), interferon-gamma (IFN gamma), tumour necrosis factor (TNF) and interleukin 1 (IL-1). After 4 days of stimulation the cell surface expression of class I and class II MHC molecules was quantitated by enzyme immunoassay. TNF by itself enhances class I expression and it synergises with IFN gamma in enhancing class I expression and inducing class II. IL-1 does not affect class I expression, nor does it synergise with IFN gamma in this respect. High doses of IL-1 slightly reduce IFN gamma mediated class II induction, but have no synergistic effect at lower doses. IFN beta stimulates class I weakly and induced class II in one experiment but the effects seen when IFN gamma and IFN beta were used together were additive, not synergistic. IFN gamma is the most potent modulator of MHC expression on these cells, although TNF acts as a strong co-stimulator, while IL-1 and IFN beta have only minor effects.

HLA-DR antigen expression on the thyrocytes of Graves' disease patients

To confirm the expression of HLA-DR antigen on the thyrocytes of Graves’ disease patients and study the relation between the degree of DR antigen expression and clinical or laboratory indices, double immunofluorescence and immunoenzymatic staining were performed on frozen thyroid sections. DR antigen was expressed on the thyrocytes of 8 of 11 patients with Graves’ disease (73%) but not found on the thyrocytes from 6 normal controls. The degree of DR antigen expression had no apparent correlation with the age, duration of the disease, activity of TBII, titers of antimicrosomal and antithyroglobulin antibody. There was no apparent spatial or quantitative relation between lymphoid follicle formation and the DR antigen expression on the thyroid follicles. But DR antigen tended to be expressed on the thyroid tissue with interstitial, lymphocyte infiltration. In conclusion, DR antigen was expressed on the thyrocytes of Graves’ disease patients but the clinical and immunological significance remains to be clarified.

Human T cells from autoimmune and normal individuals can produce tumor necrosis factor

T cell clones derived from patients with autoimmune diseases were found to be capable of producing tumor necrosis factor (TNF). This was demonstrated by stimulating the clones, in the absence of accessory cells, with antibodies against the Ti/T3 complex and with recombinant interleukin 2 (IL2). Analysis of RNA extracted from these clones showed that TNF mRNA was more abundant than lymphotoxin (LT) mRNA. We also found that TNF protein in the supernatants of these clones was generally more abundant than LT as assessed by using the murine L929 cell assay. TNF production was not limited to T cells from autoimmune individuals, since the T cell tumor HUT78 and T cells purified from the peripheral blood of healthy individuals also made TNF. Unlike the T cell clones, HUT78 produced greater amounts of LT mRNA than TNF mRNA. Induction of TNF mRNA in T cells from healthy individuals displayed a two-signal requirement (phorbol myristate 13-acetate and phytohemagglutinin or OKT3 and phorbol myristate 13-acetate), similar to that described for the induction of the T cell lymphokines IL 2 and interferon-gamma (IFN-gamma). Additionally we found that IL2 alone was sufficient to induce TNF in these cells when they had been precultured with phytohemagglutinin for 7 days to express IL 2 receptors. The cloned T cells we have characterized also produce IFN-gamma which was detected in the supernatants of the clones using a radioimmunoassay. The evidence suggests that T cells can produce TNF and have the potential to deliver by themselves the dual and synergistic signals of TNF/LT and IFN-gamma to target cells, a process which may be of importance in the pathogenesis of human autoimmunity.

The role of autoantigen in autoimmunity

Autoimmunity in disease is driven by autoantigen. Cell surface molecules may stimulate autoreactive T-helpers if class II MHC is expressed; special factors may predispose to the ease of class II induction. Soluble autoantigens may be focused by primed B cells and processed for presentation to T cells. Autoantigenicity may be influenced by metabolic events: (a) Poorly iodinated thyroglobulin does not induce thyroiditis, and (b) IgG in rheumatoid arthritis has galactose deficient Fc oligosaccharides. Glycosylation defects may prove to have wide implications.

Gene cloning and structure--function relationship of cytokines such as TNF and interleukins

The genes for a number of proteins, potentially useful in cancer therapy and collectively called "biological response modifiers", have been cloned and expressed in micro-organisms in recent years. These recombinant proteins, which are now available in pure form in nearly unlimited quantities, include interferons, interleukins and cytotoxins such as Tumor Necrosis Factor (TNF) and lymphotoxin. Most often the human gene has been cloned and expressed, with view to possible applications in medicine, but usually the mouse equivalent gene was also characterized in order to carry out syngeneic animal model experiments. TNF is selectively toxic for many transformed cell lines, either alone or in combination with interferon or inhibitors of RNA or protein synthesis. Cells sensitive to the cytotoxic action of TNF and cells unaffected by it nonetheless usually carry about an equal number of TNF receptors; hence it is the secondary, intracellular signal which makes the difference between a transformed cell and a normal, diploid cell. TNF can induce a number of different genes in a variety of cells; for example, endothelial cells express a surface antigen responsible for adherence of leucocytes. Another gene which is induced by TNF is interleukin 6 (also called 26 kDa protein or BSF-2). This interleukin, IL-6, is a growth and differentiation factor for B cells as well as for T cells; it is responsible for functions previously ascribed to hepatocyte-stimulating factor, but has no interferon activity. The toxic action of TNF on tumor cells must involve the release of arachidonic acid as phospholipase inhibitors block the TNF-induced effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of major histocompatibility complex class II subregion products by jejunal epithelium in patients with coeliac disease

The MHC class II subregion products (HLA-DR), HLA-DP, and HLA-DQ) were located by immunofluorescence in serial sections of ethanol-fixed, paraffin-embedded jejunal mucosa from control subjects and patients with coeliac disease (CD). DR staining was seen in a granular luminal distribution and basolaterally on surface epithelial cells in both untreated and treated CD patients and in controls. In untreated CD the crypt epithelium was positive for DR almost to the bottom of the glands. This contrasted with virtually absent glandular DR staining in controls and weak staining including only the upper part of the crypts in 5 out of 11 treated patients. HLA-DP was present apically in the surface epithelium in all untreated patients, in 5 out of 11 treated patients, and in 4 out of 11 controls. HLA-DQ appeared only in three untreated patients and was restricted to patches of surface epithelium. The number of intraepithelial T lymphocytes per millimetre of surface epithelium was significantly higher in untreated than in treated CD patients or controls; it was also significantly higher in specimens with epithelial DP expression than in those without. This suggested that intraepithelial lymphocytes modulate epithelial class II expression.

Molecular mapping of the human major histocompatibility complex by pulsed-field gel electrophoresis

Pulsed-field gel electrophoresis and "cosmid walking" have been used to establish a molecular map of the human major histocompatibility complex (MHC). We have isolated approximately equal to 230 kilobases (kb) of genomic DNA in overlapping cosmid clones covering the genes for the second and fourth components of complement (C2 and C4, respectively), factor B, and steroid 21-hydroxylase, and approximately equal to 82 kb of genomic DNA surrounding the genes for the tumor necrosis factors alpha and beta. Single-copy hybridization probes isolated from these cosmid clusters and probes for the known MHC gene loci were hybridized to Southern blots of genomic DNA that had been digested with infrequently cutting restriction endonucleases and separated on pulsed-field gels. The data obtained allowed the construction of a long-range genomic restriction map and indicated that the MHC spans 3800 kb. This map orients the MHC class III gene cluster with respect to the DR subregion; the C2 gene is on the telomeric side of the 21-hydroxylase B gene. In addition we have defined the positions of the genes for the tumor necrosis factors alpha and beta in the human MHC. Genes for the alpha chain of DR and 21-hydroxylase B are separated by at least 300 kb, while the distance between the genes for C2 and tumor necrosis factor alpha is 390 kb. The HLA-B locus lies approximately equal to 250 kb on the telomeric side of the tumor necrosis factor genes.

Tumor necrosis factor amplifies measles virus-mediated Ia induction on astrocytes

We describe the induction of Ia on cultured astrocytes by measles virus and the amplification of this induction by tumor necrosis factor (TNF). Measles virus induces Ia on rat astrocytes by direct interaction with these cells. TNF does not induce significant levels of Ia at any dose from 1 to 10,000 units/ml. As little as 10 units of TNF per ml, however, amplifies Ia-inducing signals generated by measles virus in astrocytes. In contrast, TNF and measles virus induce class I major histocompatibility complex (MHC) antigens, when applied individually, and TNF amplification of measles virus class I MHC induction is not apparent. The induction of either Ia or class I MHC antigens on rat astrocytes by measles virus does not depend on glial-derived soluble factors generated during infection. Since brain cells are normally lacking MHC antigens upon which T cells depend for interaction with antigen presenting cells, these data indicate that the ability of measles virus to directly stimulate MHC antigen expression and the ability of TNF to amplify Ia expression locally in the brain may be important in initiating cell-mediated immune response to viral infection.

Aberrant expression of class II major histocompatibility complex molecules by B cells and hyperexpression of class I major histocompatibility complex molecules by insulin containing islets in type 1 (insulin-dependent) diabetes mellitus

Twenty-three patients with recent onset Type 1 (insulin-dependent) diabetes in whom residual insulin secreting B cells were present and 12 patients with disease of more prolonged duration (maximum 9 years), 8 of whom had residual B cells, were studied. Aberrant expression of Class II major histocompatibility complex molecules was demonstrated immunohistochemically on insulin secreting B cells in 21 out of 23 patients with recent onset disease and 6 of the patients with more prolonged disease. No such expression was seen on glucagon secreting A cells or somatostatin secreting D cells. Islets where there was marked hyperexpression of Class I major histocompatibility complex molecules on islet endocrine cells were seen in all cases in which residual B cells were present. Ninety-two per cent of insulin containing islets but only 1% of insulin deficient islets exhibited this phenomenon (p less than 0.001, Chi-squared test). There was evidence to suggest that both these abnormalities of major histocompatibility complex expression preceded insulitis within a given islet. They also appeared to be unique to Type 1 diabetes, being absent in pancreases of patients with Type 2 (non-insulin-dependent) diabetes, chronic pancreatitis, cystic fibrosis, graft-versus-host disease and Coxsackie B viral pancreatitis. The development of autoimmunity to B cells in Type 1 diabetes may be a "multistep" process in which abnormalities of major histocompatibility complex expression on islet endocrine cells are crucial events.