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

Lymphotoxin activation by human T-cell leukemia virus type I-infected cell lines: role for NF-kappa B

Human T-cell leukemia virus type I (HTLV-I)-infected T-cell lines constitutively produce high levels of biologically active lymphotoxin (LT; tumor necrosis factor-beta) protein and LT mRNA. To understand the regulation of LT transcription by HTLV-I, we analyzed the ability of a series of deletions of the LT promoter to drive the chloramphenicol acetyltransferase (CAT) reporter gene in HTLV-I-positive MT-2 cells. The smallest LT promoter fragment (-140 to +77) that was able to drive CAT activity contained a site that was similar to the immunoglobulin kappa-chain NF-kappa B-binding site. Since the HTLV-I tax gene activates the nuclear form of NF-kappa B, this finding suggested a possible means of HTLV-I activation of LT production. We found that the LT kappa B-like site specifically formed a complex with NF-kappa B-containing nuclear extract from MT-2, C81-66-45, and other activated T cells. Mutation of the LT kappa B site in the context of the LT promoter (-293 to +77) (mutant M1) reduced the ability of the promoter to drive the CAT gene in HTLV-I-infected and noninfected human T-cell lines. These data suggest a general role for NF-kappa B activation in the induction of LT gene transcription. Activation of LT in HTLV-I-infected cells may explain the pathology associated with HTLV-I infection, including the hypercalcemia that is prevalent in adult T-cell leukemia.

Human tumour necrosis factors-alpha and -beta: differences in their structure, expression and biological properties

Tumour necrosis factor-alpha (TNF-alpha) and lymphotoxin (LT or TNF-beta) are cytokines, best known for their cytotoxic or cytostatic effects on some tumour cells. They are structurally related, compete for a common receptor, and are potent inducers of similar biological responses. TNF-alpha and LT appear to have distinct three-dimensional structures because they differ greatly in their sensitivity to various proteases and chemical agents, and antibodies raised against one cytokine do not cross-react with the other cytokine. The closely linked TNF-alpha and LT genes are independently regulated since many cell types produce only TNF-alpha or LT. Expression of the TNF-alpha gene can be controlled either at the transcriptional or at the post-transcriptional level. In some cell types, TNF-alpha and LT induce qualitatively or quantitatively different biological responses, and LT can antagonize the action of TNF-alpha. The disparate biological activities of TNF-alpha and LT may be related to their different interactions with a common receptor. It is possible that TNF-alpha and LT have different physiological roles.

Luteinization of human granulosa cells in vivo is associated with expression of MHC class II antigens

We previously described the presence of MHC class II (HLA-DR) antigens, structurally similar to those on lymphoid cells and bearing the genetically-appropriate allotypic determinants, on human adrenocortical cells in the zona reticularis of normal glands. We now report a similar expression by granulosa-lutein cells (GLC) in corpora lutea (CL) of normal ovaries, as detected by indirect immunofluorescence techniques with the use of mouse monoclonal antibodies (MAb). In some cases, GLC were also positive for HLA-DQ and -DP antigen expression. Neither granulosa nor theca interna cells in large antral follicles of the same ovaries showed any detectable expression of MHC class II antigens. Moreover, theca-lutein (paralutein) cells, identified by their reactivity with specific human autoantibodies in 5 of the 7 human CL examined, were also negative. Similarly, GLC, but not paralutein cells, in rhesus monkey CL showed significant cross-reactivity with anti-HLA-DR MAb. In contrast, lutein cells in ovaries from either cycling or 7-day-pregnant rats were negative for MHC class II (Ia) antigen expression. Expression of MHC class II antigens by human granulosa cells after their luteal transformation confirms the normal inducibility of certain human steroidogenic cells at the time of their further functional differentiation and enhanced biosynthetic activity, and suggests that these molecules may have additional functions beyond serving as restriction elements in the immune response.

Nature of the mononuclear infiltrate and the mechanism of muscle damage in juvenile dermatomyositis and Duchenne muscular dystrophy

Normal skeletal muscle does not express class I MHC antigens. In contrast, these antigens are strongly expressed at the periphery of muscle fibres in patients with juvenile dermatomyositis (JDM) and Duchenne muscular dystrophy (DMD). Interferons can induce the expression of class I antigens, but in this study interferon-gamma could not be detected in JDM muscle biopsy specimens using four different immunocytochemical techniques. However, an infiltrate of mononuclear cells capable of synthesising interferons was present in biopsies from JDM and DMD patients. The predominant cell types detected in both diseases were macrophages and T lymphocytes, these two cell types comprising more than 80% of the infiltrating mononuclear cells. A striking predominance of CD4+ helper/inducer T cells was observed. The majority of these cells expressed class II MHC antigens and were, therefore, considered to be activated. Additional evidence for the functional activity of CD4+ T cells was derived from the finding that it was this population of cells from JDM biopsies which proliferated in response to interleukin-2 in vitro. T cell subsets in peripheral blood were also investigated in JDM and DMD patients. Only in the case of JDM were any significant differences from normal observed, where a significant reduction in the number of peripheral blood CD8+ T cells resulted in an elevation of CD4+/CD/8+ ratios. The role of CD4+ T cells and aberrant class I MHC antigen expression in mediating muscle damage in JDM and DMD is discussed.

Class II (HLA-DR, -DP, and -DO) antigens on intestinal epithelia in ulcerative colitis, Crohn's disease, colorectal cancer and normal small intestine

Class II antigens in involved colonic epithelia of ulcerative colitis (UC), Crohn's disease (CD), colorectal cancer, and epithelia of normal small intestine were investigated using an immunoperoxidase method. Ten normal colonic mucosa served as normal controls. Ten specimens were studied for each group. Normal colonic epithelia did not express class II antigens. In colonic diseases; (1) with regard to the frequency and extent of class II antigens on epithelia. HLA-DR antigens were the most highly and greatly expressed, followed by HLA-DP and then HLA-DQ antigens. (2) The extent of HLA-DR and -DP, but not HLA-DQ, expression on epithelia of UC and colorectal cancer seemed to be positively correlated with the degree of mononuclear cell infiltration in the lesion. (3) The extent of class II antigen expression on colonic epithelia in CD was not related to the degree of mononuclear cell infiltration in the lesion. (4) The extent of HLA-DR and -DP expression on epithelia of colorectal cancer seemed to be positively correlated with increasing undifferentiation. In the normal small intestine, where HLA-DR antigens were physiologically expressed on epithelia. HLA-DQ antigens were not expressed. The heterogeneity among colonic diseases, and between the physiological and pathological status, may reflect differences in immunoregulation.

Detection of transforming growth factor-beta in rheumatoid arthritis synovial tissue: lack of effect on spontaneous cytokine production in joint cell cultures

The presence of transforming growth factor-beta (TGF-beta) in inflammatory joint disease was investigated. Synovial fluid from patients with rheumatoid arthritis (RA) and patients with other non-autoimmune inflammatory joint diseases contained high levels of both active and latent TGF-beta. Levels of active TGF-beta did not correlate with drug regimen in either patient group or with the recovery period in the individuals with non-RA joint disease. Freshly isolated synovial cells from individuals with RA were shown by Northern blotting to express the mRNA for TGF-beta 1 and to secrete latent TGF-beta protein which could be neutralized by antibodies to TGF-beta 1 and TGF-beta 2. Lipopolysaccharide-stimulated peripheral blood mononuclear cells from normal donors produced interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha) which was inhibited by pretreatment of these cells with recombinant TGF-beta. Cytokine production was not inhibited if the addition of TGF-beta was used after the inducing stimulus, suggesting that in activated cells cytokine production cannot be inhibited. This was confirmed by the observation that neither TGF-beta 1 or TGF-beta 2 inhibited spontaneous IL-1 or TNF-alpha production by rheumatoid synovial mononuclear cells in culture. These findings show that despite the presence of active TGF-beta in RA synovial joints and the spontaneous production of latent (potentially active) TGF-beta by RA cells in culture, additional TGF-beta did not inhibit ongoing cytokine synthesis in vitro. This suggests that TGF-beta may not inhibit cytokine production in the rheumatoid joint although it cannot be ruled out that in vivo TGF-beta already has an immunosuppressive effect which cannot be further increased in vitro by exogenous protein.

Differential regulation and expression of major histocompatibility complex (MHC) and Ly-6 gene products on mouse testicular Leydig and Sertoli cell lines

The expression and regulation of Class I and Class II major histocompatibility complex (MHC) and Ly-6 antigens were examined in BALB/c testicular cells. Studies were performed utilizing differentiated murine Leydig (TM3) and Sertoli (TM4) cell lines. Neither Class I (Dd) nor Class II (IA/Ed) MHC antigens were detectable on untreated TM3 cells. However, concanavalin-A activated spleen cell supernatant (Con-A sup) or interferon-gamma (IFN-gamma) treatment resulted in the marked induction of both Class I and Class II MHC antigens on virtually all of the Leydig cells. MHC Class II mRNA, which was not detected in resting cells, was clearly induced following IFN-gamma incubation. Sertoli cells were found to constitutively express low levels of Class I (Dd) but not Class II (IA/Ed) antigens. However, in contrast to the enhanced MHC expression in TM3 cells, Con-A sup or IFN-gamma treatment of TM4 cells resulted in marked augmentation of Class I, but not Class II, MHC antigens. Northern blot analysis failed to detect Class II mRNA in either the resting or IFN-gamma treated TM4 populations. Neither ethanol nor tumor necrosis factor (TNF) alone, or together with IFN-gamma head significant effects on MHC expression by TM3 and TM4 cells. Ly-6 antigens, predominantly expressed on hematopoietic cells, were found to be present on both TM3 and TM4 cells. Expression of this non-MHC encoded product was also shown to be markedly enhanced by IFN-gamma treatment on both testicular cell lines. In total, these findings demonstrated that cytokines can differentially affect discrete cell populations arising from a particular tissue with respect to the un-regulation of MHC and non-MHC gene products. These findings are discussed in the context of autoimmune responses directed against this tissue.

Tumor necrosis factor beta and ultraviolet radiation are potent regulators of human keratinocyte ICAM-1 expression

Intercellular adhesion molecule-1 (ICAM-1) functions as a ligand of leukocyte function-associated antigen-1 (LFA-1), as well as a receptor for human picorna virus, and its regulation thus affects various immunologic and inflammatory reactions. The weak, constitutive ICAM-1 expression on human keratinocytes (KC) can be up-regulated by cytokines such as interferon-gamma (IFN gamma) and tumor necrosis factor alpha (TNF alpha). In order to further examine the regulation of KC ICAM-1 expression, normal human KC or epidermoid carcinoma cells (KB) were incubated with different cytokines and/or exposed to ultraviolet (UV) radiation. Subsequently, ICAM-1 expression was monitored cytofluorometrically using a monoclonal anti-ICAM-1 antibody. Stimulation of cells with recombinant human (rh) interleukin (IL) 1 alpha, rhIL-4, rhIL-5, rhIL-6, rh granulocyte/macrophage colony-stimulating factor (GM-CSF), rh interferon alpha (rhIFN alpha), and rh transforming growth factor beta (TGF beta) did not increase ICAM-1 surface expression. In contrast, rhTNF beta significantly up-regulated ICAM-1 expression in a time- and dose-dependent manner. Moreover, the combination of rhTNF beta with rhIFN gamma increased the percentage of ICAM-1-positive KC synergistically. This stimulatory effect of rhTNF beta was further confirmed by the demonstration that rhTNF beta was capable of markedly enhancing ICAM-1 mRNA expression in KC. Finally, exposure of KC in vitro to sublethal doses of UV radiation (0-100 J/m2) prior to cytokine (rhIFN tau, rhTNF alpha, rhTNF beta) stimulation inhibited ICAM-1 up-regulation in a dose-dependent fashion. These studies identify TNF beta and UV light as potent regulators of KC ICAM-1 expression, which may influence both attachment and detachment of leukocytes and possibly viruses to KC.

Tolerance in transgenic mice expressing major histocompatibility molecules extrathymically on pancreatic cells

Transgenic mice with defined expression of major histocompatibility complex (MHC) proteins provide novel systems for understanding the fundamental question of T cell tolerance to nonlymphoid self components. The MHC class II I-E and I-A and class I H-2K molecules expressed specifically on pancreatic islet or acinar cells serve as model self antigens. In these systems, transgenic proteins are not detected in the thymus or other lymphoid tissues. Yet mice are tolerant to the pancreatic MHC products in vivo; this tolerance is not induced by clonal deletion. These studies have been aided by monoclonal antibodies specific for I-E-reactive T cells and indicate that clonal anergy may be an important mechanism of tolerance to peripheral proteins.

Relation between T cell number and epithelial HLA class II expression quantified by image analysis in normal and inflamed human gastric mucosa

Epithelial expression of HLA class II determinants and the number of lamina propria and intraepithelial T cells were quantified in gastric body mucosa by means of paired immunofluorescence staining which was subjected to computerised image analysis. In normal mucosa, epithelial HLA-DR expression was virtually absent. A significantly increased expression was seen in simple chronic gastritis, most extensively in the isthmus zone, where a positive reaction was seen in 34% of the epithelial area when the gastritis was of low degree and in 85% when it was of moderate severity. The most extensive HLA-DR expression was found in moderate 'stump gastritis' 28 to 32 years after Billroth II resections. In these patients the epithelial area in the foveolar and isthmus zones showed 83% and 92% positive responses, respectively. The HLA subregion products were expressed in a differential manner (DR greater than DP greater than DQ). The number of both intraepithelial and lamina propria T cells increased significantly with increasing severity of gastritis, and the fraction of putative memory T cells was also raised. Correlation analyses showed a positive relation between the epithelial expression of HLA-DR and the intraepithelial as well as the lamina propria density of T cell. These results suggest a biological link between T cells, aberrant HLA-DR expression, and gastritis, although the pathogenic importance of this relation is unknown. Enhanced epithelial presentation of autoantigens or luminal antigens, or both leading to increased activation of T cells is one possible explanation.

Tumor necrosis factor inhibitor: purification, NH2-terminal amino acid sequence and evidence for anti-inflammatory and immunomodulatory activities

The urine of some febrile patients has been shown to contain a tumor necrosis factor-alpha-inhibiting activity (TNF-alpha INH) when tested in a cytotoxicity assay using the TNF-susceptible cell line L-929. The inhibitor was purified to homogeneity using a simple three-step procedure which included a TNF-alpha affinity column, cation exchange and reverse-phase chromatography. The NH2-terminal amino acid sequence of the inhibitor showed no sequence similarity with proteins in the data bases used. Using gel filtration, it was shown that TNF-alpha and the inhibitor form a stable complex which eluted with a molecular weight of about 75,000. This value corresponds to the sum of the inhibitor (approximately 30,000) and TNF-alpha (approximately 45,000-50,000) molecular weight. The TNF-alpha INH blocked prostaglandin E2 production by dermal fibroblasts in a dose-dependent manner, providing evidence for antiinflammatory activity. TNF-alpha INH also blocked class I antigen expression in a dose-dependent manner as measured using the human Colo 205 tumor cell line. Furthermore, TNF-alpha INH affected TNF-alpha synergism with IFN-gamma-induced HLA-DR antigen expression but had no effect on IFN-gamma activity. The data presented demonstrate that TNF-alpha bioactivity can be regulated at the protein level.

The inhibitory effect of tumor necrosis factor and interleukin-1 on Ia induction by interferon-gamma on endothelial cells from murine central nervous system microvessels

The effect of both tumor necrosis factor-alpha (TNF) and interleukin-1 (IL-1) on interferon-gamma (IFN)-induced Ia expression was studied using cultured endothelial cells (EC) isolated from cerebral microvessels of SJL mice. TNF inhibited Ia induction by IFN in a dose-dependent manner. The degree of inhibition by TNF was related to the IFN concentration: 200 U/ml TNF inhibited Ia expression induced by 20 U/ml IFN by 80% and Ia induced by 100 U/ml IFN by 45%. FACS analysis revealed the induction of Ia antigen on 30-40% of EC after 3 days' culture with IFN; TNF significantly reduced the percent of EC expressing Ia antigens. Identical treatment of SJL astrocytes showed TNF augmented Ia expression induced by IFN. IL-1 also inhibited Ia induction by IFN in a manner similar to that observed with TNF. The percent reduction of Ia-positive EC by Il-1 (2.0 U/ml) was 30% and 50% during incubations with 100 and 20 U/ml IFN, respectively. When combined at suboptimal concentrations IL-1 and TNF synergistically inhibited Ia expression induced by IFN. These results demonstrate that TNF acts on EC and astrocytes in a disparate manner and indicate that TNF and IL-1 can synergistically down-regulate immune responses involving central nervous system EC.

A new view of the beta cell as an antigen-presenting cell and immunogenic target

Cellular autoimmunity is thought to be primarily responsible for the selective destruction of islet beta cells in Type I diabetes. Why the T lymphocyte reacts to self and recognizes the beta cell as foreign, as against the other endocrine islet cells, is unknown. One key issue is whether the beta cell itself is capable of presenting autoantigen(s) and thereby breaking T lymphocyte tolerance. In this paper we discuss current concepts of antigen presentation and relate these to recent findings from our laboratory, suggesting that the beta cell can be induced to display many of the phenotypic properties of classical antigen-presenting cells, including induction of MHC and ICAM-1 expression and production of IL-6. Finally, a model is presented which provides a new view of the initiation and perpetuation of autoimmune beta-cell destruction in Type I diabetes.

Autologous CD4 T-cell responses to ectopic class II major histocompatibility complex antigen-expressing single-cell islet cells: an in vitro insight into the pathogenesis of lymphocytic insulitis in nonobese diabetic mice

We investigated by flow cytometric analysis the expression of class II major histocompatibility complex (MHC) molecules by viable single-cell islet cells (SCICs) prepared from male and female 4- and 10-week-old nonobese diabetic (NOD) mouse islets. With anti-I-Ak monoclonal antibody (specific for I-Ak,f,r,s beta and produced by clone 11-5-2), and fluorescein isothiocyanate-conjugated goat anti-mouse IgG as second-step antibody, we found that SCICs from both sexes aberrantly expressed class II MHC molecules, which was not altered after SCICs were cultured for 24 hr or 120 hr in the presence of 10 ng of recombinant murine interferon gamma per ml. Double-indirect immunofluorescence of male SCICs indicated that the expression of class II MHC molecules was a property of beta cells. Control experiments documented that macrophages and mononuclear cells did not contaminate the SCIC preparations. Coculture experiments with responder splenic CD4 T cells isolated from diabetic NOD mice and stimulator male SCICs indicated a recognition event evidenced by a 12-fold increase in proliferative response. Monoclonal antibodies to class II MHC and CD4 antigens blocked the proliferative response. Results from control autologous and allogeneic mixed lymphocyte reactions suggest that the responder CD4 T cells are autoreactive self-class II MHC restricted. We tentatively conclude that the ability of SCICs from both sexes of NOD mice to express class II MHC molecules as early as 4 weeks of age may represent a mechanism for targeting immune reactions to beta cells and initiate lymphocytic insulitis.

Interferon-gamma sensitizes rat pancreatic islet cells to lysis by cytokines and cytotoxic cells

Immunoregulatory polypeptides (cytokines) produced by mononuclear cells of the immune system can inhibit insulin secretion and may be cytotoxic to pancreatic islet beta cells. We used a modified 51Cr release cytotoxicity assay to define the interactive cytotoxic effects of interleukin-1 (IL-1), tumor necrosis factor (TNF), and interferon gamma (IFN-gamma) on rat islet cells in monolayer culture. We here demonstrate that (a) IFN-gamma, but not IL-1 or TNF, can sensitize islet cells to subsequent cytolysis by other cytokines (IL-1 or TNF); (b) the cytolytic effect of sequential addition of IFN-gamma, then IL-1 or TNF (approximately 35-40% 51Cr release) is similar to that produced by the concurrent addition of IFN-gamma plus IL-1 or TNF; (c) the priming effect of IFN-gamma persists for 3 to 6 or more days after its removal; and (d) islet cells preincubated with IFN-gamma are also more sensitive to cytolysis by splenic mononuclear cells from diabetes-prone BB/Wor rats. These findings suggest that IFN-gamma produced by activated T lymphocytes and monocytic cells infiltrating islets in Type 1 diabetes may play a direct and important role in sensitizing beta cells to damage by other cytokines (IL-1, TNF) and cytotoxic cells in the immune/inflammatory infiltrate.

Inappropriate major histocompatibility complex expression on cardiac tissue in dilated cardiomyopathy. Relevance for autoimmunity?

The inappropriate expression of major histocompatibility complex (MHC) molecules on epithelial and endothelial cells is a recognized marker of autoimmune disease. An autoimmune pathogenesis has been suspected in dilated cardiomyopathy (DCM). In the normal heart, MHC products are usually not detectable on myocytes using immunochemical techniques. MHC molecule expression has not, however, been assessed on cardiac endothelial cells. The aim of this study was to investigate possible autoimmune phenomena and MHC molecule expression in fresh endomyocardial biopsies from 29 patients with DCM. These were compared with those observed in surgical specimens from 63 patients with other acquired cardiac disease and from 22 with congenital heart disease (CHD) as normal controls. Conventional immunofluorescence (IFL) with monoclonal antibodies (MoAbs) to lymphocyte and macrophage markers and to MHC molecules was employed, and double IFL with antiserum to human Factor VIII was used for the identification of endothelial cells. Myocytes did not express MHC molecules in either DCM or controls. In normal hearts, Class II molecules were detected on endothelial and endocardial cells in only a few cases (3/22 and 2/22 respectively). By contrast, endothelial and endocardial cells inappropriately expressed Class II in a high proportion of DCM patients (28/29 and 22/29) but less frequently in other acquired cardiac diseases (19/63, P less than 0.001 and 11/63, P less than 0.001 respectively). In all the DCM biopsies examined there was a hierarchy of Class II subloci product expression (DR greater than DP greater than DQ); lymphocytic infiltration was a rare finding and macrophages/dendritic cells were not prominent. The finding of inappropriate MHC Class II molecule expression on cardiac endothelial and on endocardial cells suggests a possible pathogenic role for these cells in the initiation and/or perpetuation of DCM.

Changes in the expression of idiotype antigen on murine B-cell lymphoma after hyperthermia alone and in combination with interferon and tumour necrosis factor

The effect of interferon (IFN) and tumour necrosis factor (TNF), either alone or combined with hyperthermia, on cell proliferation and expression of idiotype antigen on a murine B-cell lymphoma has been studied. Incubation with same doses of IFN-alpha and IFN-gamma reduced cell proliferation to the same extent. Hyperthermia potentiated the antiproliferative activity of IFN-alpha and IFN-gamma. Pretreatment with IFN-gamma induced a synergistic response with heat, while IFN-alpha and heat had an additive effect. Tumour necrosis factor (TNF) alone did not affect cell proliferation, nor did TNF modify the heat-induced delay in cell growth. The quantitative expression of surface idiotype antigen was studied by flow cytometry using an anti-idiotype monoclonal antibody (MAb). Heat reduced the expression of idiotype antigen approximately 50%. The duration of the reduction depended on the heat-dose. Recovery of antigen expression correlated with recovery of cell growth, and 2-5 days after the treatment antigen expression returned to the normal level for untreated cells. IFN-gamma and TNF increased antigen expression (30-50%) which lasted for 4-6 days after treatment. When cells were incubated with IFN-gamma or TNF for 2 days prior to hyperthermia, the increase in antigen expression was observed immediately after heating, but by the following day, antigen expression was similar to that after heat treatment alone. Expression of idiotype antigen recovered within 2-5 days to the same values as after heat treatment alone. IFN-alpha alone or combined with hyperthermia did not have any significant effect on antigen expression.

Mechanism of human lymphotoxin and tumor necrosis factor induced destruction of cells in vitro: phospholipase activation and deacylation of specific-membrane phospholipids

The role of phospholipase (PLase) activation and lipid metabolism in lymphotoxin (LT)- and tumor necrosis factor (TNF)-mediated destruction of murine L929 cells was examined. At the levels of LT and TNF employed, cell destruction began at 4-6 h and was 99% complete by 30 h. Cell membrane phospholipids (PL), labelled in situ at the C2 position with 14C arachidonic acid, were analyzed by two-dimensional thin-layer chromatography and quantitated over a 30 h time course after LT or TNF treatment. The ratio of radiolabel incorporation relative to the actual amount of each PL present was determined by inorganic phosphate analysis. Radiolabelled arachidonic acid, eicosanoids, and neutral lipids were released into the medium prior to the onset of cell death (4-6 h) and continued to accumulate linearly throughout the destructive reaction. There was a quantitative relationship between the appearance of radiolabelled metabolites in the media and the loss of radiolabelled cellular PL. Cellular phosphatidylethanolamine was the primary PL deacylated by PLase action, showing a 75% reduction in radiolabel. The PLase inhibitors--quinacrine, hydrocortisone, dexamethasone, and indomethacin--were potent inhibitors of LT- and TNF-mediated cell destruction, suggesting that selective deacylation of specific membrane PL by PLase activation is an important step in the events that lead to LT- and TNF-mediated cellular destruction in vitro.

Synergistic induction of polypeptides by tumor necrosis factor and interferon-gamma in cells sensitive or resistant to tumor necrosis factor: assessment by computer based analysis of two-dimensional gels using the PDQUEST system

Tumor necrosis factor (TNF) synergistically enhanced the antiproliferative activity of interferon-gamma (IFN-gamma) in both TNF-sensitive and TNF-resistant variants of the cervical carcinoma line, ME-180. TNF alone had no apparent effect on the levels of synthesis of individual proteins in either of these variant cell lines as assessed by computerized two-dimensional gel analysis of cell lysates using the PDQUEST system. However, IFN-gamma enhanced the levels of 18 polypeptides and suppressed the levels of 10 polypeptides in both cell lines. When used in combination in both cell lines, TNF and IFN-gamma induced the synthesis of 10 polypeptides that were not induced by either agent alone. These synergistically induced polypeptides may be crucial to the mechanism of the synergistic antiproliferative action of TNF and IFN-gamma in ME-180 cells.

Liver-derived T cell clones in autoimmune chronic active hepatitis: accessory cell function of hepatocytes expressing class II major histocompatibility complex molecules

Thirty T cell clones were generated from T cell blasts, infiltrating the liver of autoimmune chronic active hepatitis (CAH) patients, stimulated with autologous hepatocytes expressing class II major histocompatibility complex (MHC) molecules and interleukin 2 (IL2). Sixteen clones were CD4+ and 14 were CD8+; all were CD25+ and WT31+, revealing that all cell lines expressed the alpha/beta chains of T cell receptor. Five CD4+ and 4 CD8+ T clones proliferated in response to hepatocytes expressing both class I and class II antigens. The hepatocyte recognition was MHC restricted because only class II MHC-matched hepatocytes were able to stimulate the CD4+ T clones, while only class I-matched hepatocytes stimulated CD8+ T clones, and because MoAbs to monomorphic determinants of class II antigens or to class I antigens appeared to block the response of the CD4+ and CD8+ T clones, respectively. These findings, together with the observation that autologous irradiated peripheral blood mononuclear cells (iPBMC) were unable to stimulate the clones, indicate that the response of these clones was directed to a liver membrane antigen in association with class II or class I MHC molecules on the surface of the hepatocytes. All the CD8+ T clones and 5 CD4+ T clones expressed high cytotoxic activity in a lectin-dependent cell-mediated cytotoxicity assay; 10 CD8+ and 3 CD4+ T clones also showed natural killer (NK)-like function. The cytolytic machinery was also present in those clones (both CD8 and CD4) recognizing the HLA-matched hepatocytes. All liver-derived T clones were able to produce high amounts of interferon (IFN)-gamma, as well as being capable of secreting IL2, following PHA stimulation.

Genes encoding tumor necrosis factor alpha and granzyme A are expressed during development of autoimmune diabetes

Progressive destruction of the insulin-producing beta cells in nonobese diabetic mice is observed after infiltration of the pancreas with lymphocytes [Makino, S., Kunimoto, K., Muraoka, Y., Mizushima, Y., Katagiri, K. & Tochino, Y. (1980) Exp. Anim. (Tokyo) 29, 1-13]. We show that the genes for tumor necrosis factor alpha and granzyme A, a serine protease associated with cytoplasmic granules of cytotoxic cells, are expressed during the development of spontaneous diabetes mellitus in the nonobese diabetic mouse. Granzyme A-positive cells are found both in and surrounding the islets, implying induction prior to islet infiltration. Tumor necrosis factor alpha expression is exclusively observed in the intra-islet infiltrate, predominantly in lymphocytes adjacent to insulin-producing beta cells, the targets of the autoimmune destruction, implying that tumor necrosis factor alpha expression is induced locally--i.e., in the islet. A considerable portion of cells expressing tumor necrosis factor alpha appear to be CD4+ T cells. This T-cell subset was previously shown to be necessary for development of the disease. Thus, these findings may be important for understanding the pathogenesis of autoimmune diabetes mellitus and potentially also for that of other T-cell-mediated autoimmune diseases.

Sequence elements required for activity of a murine major histocompatibility complex class II promoter bind common and cell-type-specific nuclear factors

We have examined the sequence elements and corresponding DNA-binding factors required for transient expression of the A alpha d promoter fused to the bacterial chloramphenicol acetyltransferase reporter gene in a variety of cultured cell lines. Deletion analysis demonstrated that only about 110 nucleotides of sequence 5' of the transcription start site are required for constitutive expression in the murine B-lymphoma cell line A20 or for gamma interferon-induced expression in the murine monocytic cell line WEHI-3. Linker-scanner mutation of this region indicated that at least three sequence elements are required for promoter activity. These elements correspond to the conserved sequence elements found in other human and mouse class II genes, the X box, the Y box, and the H box. Analysis of DNA-binding activity showed that the three most predominant factors present in extracts from WEHI-3, A20, or L cells (which do not express the class II genes) are actually a family of factors that bind to a fourth sequence element, overlapping the 3' end of the X-box sequence, that is homologous to the cyclic AMP-responsive enhancer element. A single common factor that binds to the Y box was detected in extracts from all cells tested, as has been seen with the Y-box elements of other class II genes. Another common factor was found that binds to the more conserved 5' region of the X-box element, although A20 extracts contained a second, distinct binding activity for this region. A common binding factor for the H-box element was detected in extracts from WEHI-3 and L cells. However, this activity was absent in A20 cell extracts. Instead, two different H-box-binding activities were detected, suggesting that different components are involved in class II gene expression in B cells and macrophages. Finally, gamma interferon treatment did not significantly alter the DNA-binding activity in WEHI-3 cells for any of the sequence elements shown to be required for induced chloramphenicol acetyltransferase expression.

Prevention of diabetes in nonobese diabetic mice by tumor necrosis factor (TNF): similarities between TNF-alpha and interleukin 1

The role of tumor necrosis factor alpha (TNF-alpha) in the pathogenesis of autoimmune diabetes mellitus was tested in the nonobese mouse (NOD) model system. The effects of TNF-alpha were assessed on three levels: (i) insulitis development, (ii) development of overt diabetes, (iii) adoptive transfer of diabetes by splenic lymphocytes. Spontaneous diabetes mellitus was blocked in NOD mice by long-term treatment with recombinant TNF-alpha. Treatment with TNF-alpha caused a significant reduction in the lymphocytic infiltration associated with the destruction of the insulin-producing beta cells. Class II major histocompatibility complex Ia expression by islet cells was not up-regulated by TNF-alpha. Moreover, TNF-alpha was able to suppress the induction of diabetes in adoptive transfer of lymphocytes from diabetic female mice to young nondiabetic male NOD mice. These activities of TNF-alpha were shared by interleukin 1 alpha in this system. These studies have implications for the pathogenesis and therapy of autoimmune diabetes mellitus.

Sequence elements required for activity of a murine major histocompatibility complex class II promoter bind common and cell-type-specific nuclear factors

We have examined the sequence elements and corresponding DNA-binding factors required for transient expression of the A alpha d promoter fused to the bacterial chloramphenicol acetyltransferase reporter gene in a variety of cultured cell lines. Deletion analysis demonstrated that only about 110 nucleotides of sequence 5' of the transcription start site are required for constitutive expression in the murine B-lymphoma cell line A20 or for gamma interferon-induced expression in the murine monocytic cell line WEHI-3. Linker-scanner mutation of this region indicated that at least three sequence elements are required for promoter activity. These elements correspond to the conserved sequence elements found in other human and mouse class II genes, the X box, the Y box, and the H box. Analysis of DNA-binding activity showed that the three most predominant factors present in extracts from WEHI-3, A20, or L cells (which do not express the class II genes) are actually a family of factors that bind to a fourth sequence element, overlapping the 3' end of the X-box sequence, that is homologous to the cyclic AMP-responsive enhancer element. A single common factor that binds to the Y box was detected in extracts from all cells tested, as has been seen with the Y-box elements of other class II genes. Another common factor was found that binds to the more conserved 5' region of the X-box element, although A20 extracts contained a second, distinct binding activity for this region. A common binding factor for the H-box element was detected in extracts from WEHI-3 and L cells. However, this activity was absent in A20 cell extracts. Instead, two different H-box-binding activities were detected, suggesting that different components are involved in class II gene expression in B cells and macrophages. Finally, gamma interferon treatment did not significantly alter the DNA-binding activity in WEHI-3 cells for any of the sequence elements shown to be required for induced chloramphenicol acetyltransferase expression.

Induction of MHC class II antigen in cultured bovine ciliary epithelial cells

The expression of major histocompatibility complex (MHC) class II antigens in cultured bovine ciliary epithelial cells was investigated by means of indirect immunohistochemistry and immunocytofluorometry. Ciliary epithelial cells grown in control tissue-culture medium did not express MHC class II. However, after incubation with bovine gamma-interferon (IFN-G) in concentrations as low as 0.3 units/ml, nearly all cells stained for MHC class II. Tumor necrosis factor increased IFN-G-induced MHC class II expression. A reduction in IFN-G-induced MHC class II expression was observed with dexamethasone, prostaglandin E2 and alpha-interferon. To test whether MHC class II expression in response to IFN-G was specific for the ciliary epithelium, several intraocular tissues were grown in culture and incubated with IFN-G. MHC class II expression was observed in all tissues tested for response to IFN-G, but at different sensitivities. Retinal pigment epithelium and ciliary epithelium exhibited the highest sensitivity, followed by corneal endothelium and lens epithelium; the lowest sensitivity was observed for retinal vascular pericytes. The results are discussed in the context of MHC class II expression on the ciliary epithelium in anterior uveitis.

Monoclonal antibody MAC 387 recognizes a myelomonocytic antigen shared by epithelial cells in inflammatory skin diseases

The monoclonal antibody MAC 387 recognizes an antigen expressed by human macrophages and granulocytes. Normal epidermis does not react with the antibody, but the inflamed epidermis may react. In this immunocytochemical study we have investigated the intracytoplasmic expression of the MAC 387 antigen in biopsies of a variety of skin disorders. In lichen planus the basal cells were usually negative, whilst suprabasal cells were positive. In the majority of other inflammatory dermatoses studied, there was positive staining of basal and suprabasal cells. A parallel frozen- and paraffin-section study of biopsies of cutaneous T-cell lymphomas and inflammatory conditions failed to demonstrate HLA Class II expression in the cytoplasm of keratinocytes. Expression of the MAC 387 antigen in the epidermis is directly associated with cell-mediated activity in the papillary dermis, but is not related to HLA Class II expression.

HLA DR, DP, DQ induction in human islet beta cells by the cytokine combination IFN-gamma + TNF-alpha

Human islet beta cells do not express HLA Class II normally, yet, in the diabetic pancreas, beta cells are selectively positive for Class II and this may facilitate their recognition by T cells. It has been demonstrated that human beta cells can be induced to express Class II when cultured with IFN-gamma + TNF-alpha or IFN-gamma + TNF-beta. To assess whether or not they can be induced to express the products of the Class II subregions, DR, DP and DQ, human islet cultures from 10 pancreas were supplemented with the combination of IFN-gamma + TNF-alpha using MoAbs specific for DR, DP and DQ products, and antibodies to insulin and glucagon. The combination IFN-gamma + TNF-alpha (100-1000 U/ml each) was able to induce the expression of the three subregions in both beta and alpha cells. The induction of subregion expression followed the hierarchy DR greater than DQ greater than or equal to DP. The capability of beta cells to express all three Class II subregions supports the possibility that these cells can present their self antigens to T cells.

Molecular basis of human leukocyte antigen class II disease associations

This chapter focuses strictly on the HLA MHC class II genes and molecules with regard to how they contribute to better delineation of the genetic associations and how the current knowledge of their structure, expression, and functions can be used to speculate on their role in the pathogenesis of disease. Because of the strong linkage disequilibrium between loci and alleles, the chapter restricts the description of the genetic associations to only the most recent data, mainly generated by molecular means, and because they supercede in precision and accuracy the previous data obtained by serological methods. Because the HLA system displays the unusual feature of strong linkage disequilibrium between loci and alleles, the genetic traits found to be associated with disease do not emerge at random. The pattern of genetic associations follow an almost constant trend. The associations gain strength each time an additional locus centromeric to the precedent is individualized. The advances made in this respect almost parallel the introduction of progressively more refined typing procedures, which allow the division of former genetic entities (loci and alleles) into additional subtypes. Among the HLA-associated diseases, or at least for those diseases in which an autoimmune process is suspected to be directly relevant to the pathogenesis, the associations are with genes and molecules of the HLA-D region (HLA class II genes and products). The most recent data assigns the disease susceptibility to common amino acid sequences present on an HLA class II molecule within its “active” site.

TNF-alpha gene polymorphisms: association with type I (insulin-dependent) diabetes mellitus

The localization of TNF genes on the short arm of chromosome 6 between HLA B and the complement genes focused attention to that genetic region which harbors many immunologically relevant genes and is also thought to hold susceptibility genes for a variety of autoimmune diseases that are linked to specific alleles of particular loci in the HLA D region. Since the recently established HLA-DR-DQ variation accounts only for part of the genetic susceptibility to insulin-dependent diabetes mellitus (IDDM) we searched for genomic variation of the tumour necrosis factor (TNF) alpha. We have identified a TNF-alpha restriction fragment length polymorphism (RFLP) with NcoI and analysed diabetic patients including their families, controls and homozygous typing cell lines (HTC) defined by the 10th International Histocompatibility Workshop. Segregation analysis in families and HTC results show a strong linkage of the TNF-alpha 5.5 kb allele with DR types in particular with A1B8DR3. This tight linkage of TNF-alpha alleles with extended haplotypes and the significant increase of heterozygotes in patients could lead to some explanation of the DR3 association with a variety of autoimmune diseases particularly IDDM.

Tumor necrosis factor-alpha enhances interferon-gamma-mediated class II antigen expression on astrocytes

Astrocytes can function as antigen-presenting cells (APC) upon expression of class II antigens, which are induced by interferon-gamma (IFN-gamma). Tumor necrosis factor-alpha (TNF-alpha) can act synergistically with IFN-gamma with respect to class II expression on a variety of cells. As brain cells themselves can secrete TNF-like factors upon stimulation, we examined the effect of TNF-alpha on IFN-gamma-mediated class II induction on astrocytes. TNF-alpha alone had no effect on class II expression, but did synergize with IFN-gamma for enhanced expression of class II antigens. The specificity of TNF-alpha activity was demonstrated by blocking the amplifying effect of TNF-alpha with a polyclonal anti-TNF-alpha antibody. Kinetic analysis of the synergistic effect indicated that optimal TNF-alpha enhancement of class II expression was observed when astrocytes were pretreated with IFN-gamma 12-24 h prior to TNF-alpha addition. A possible mechanism for the synergistic action between IFN-gamma and TNF-alpha may be increased TNF-alpha receptor expression by IFN-gamma. Astrocytes treated with IFN-gamma for 24 h express more TNF-alpha receptors (3900/cell) than do untreated astrocytes (2483/cell), with no significant change in the binding affinity (Kd). These results suggest that the synergistic activity of TNF-alpha requires an inductive signal from IFN-gamma, which in part may be increased TNF-alpha receptor expression. Altogether, our observations indicate that TNF-alpha enhances ongoing class II major histocompatibility complex gene expression in rat astrocytes, which in this system is initially induced by IFN-gamma. TNF-alpha exerts its effect by binding to high affinity TNF-alpha receptors on astrocytes, whose expression is also enhanced by IFN-gamma. These two cytokines work in concert to elevate class II expression on astrocytes, an event which can contribute to initiation and/or perpetuation of intracerebral immune responses.

2'-5' oligoadenylate synthetase and its relationship to HLA and genetic markers of insulin-dependent diabetes mellitus

Cytokines and their related enzyme pathways may play a part in the development of insulin-dependent diabetes mellitus (IDDM). We have therefore studied the activity of the enzyme 2'-5' oligoadenylate synthetase (which is induced by both interferon and the tumour necrosis factors) in circulating mononuclear cells from 40 subjects with IDDM and 32 healthy control subjects. There was no difference in mean basal enzyme activity between the two groups. A polymorphism of the 2'-5' oligoadenylate synthetase gene, not previously described, was found using the restriction enzyme Bam HI. There was no association of 2'-5' oligoadenylate synthetase genotypes with IDDM, but there was a significant correlation between basal 2'-5' oligoadenylate synthetase activity and 2'-5' oligoadenylate synthetase genotypes. Significantly higher mean basal levels of 2'-5' oligoadenylate synthetase activity were associated with HLA-DQA 4.6 phenotype (determined using the restriction enzyme Taq 1 and a DQA probe) and HLA-DR3 (determined serologically), whereas significantly lower mean levels of enzyme activity were associated with HLA-DQA 5.5 and HLA-DR7, in both IDDM and control subjects. An analysis of variance confirmed that these associations were independent 2'-5' oligoadenylate synthetase genotype. Likewise, a significantly higher mean level of enzyme activity was associated with the heterozygous 1/3 insulin-related genotype in the IDDM subjects only. This study therefore suggests that the possession of certain HLA haplotypes might be associated with differing levels of basal 2'-5' oligoadenylate synthetase activity.

[Recent aspects of the pathogenesis of endocrine autoimmune diseases in the human: what role does expression of class II HLA molecules in the endocrine target cell play?]

The inappropriate expression of HLA Class II molecules by the target cells of endocrine autoimmune diseases is a recent observation that has been intensively studied in thyroid autoimmunity and type I diabetes mellitus. In vitro studies have shown that interferon-gamma can induce Class II expression, either alone, as in thyrocytes, or in combination with other mediators like tumour necrosis factor or lymphotoxin, as in islet cells, pointing to possible mechanisms operating in vivo. Endocrine cells expressing Class II molecules are able to present their autoantigens to helper T cells, thus possibly inducing the autoimmune process. However, until now it is still unclear if the expression of Class II molecules by the target cells is the primary immune phenomenon, which might possibly be triggered by a latent viral infection of the endocrine cell. Alternatively, it might be a secondary response in an ongoing autoimmune process. Particularly data obtained in the diabetic pancreas favour the first possibility, but only progress in our understanding of the role of HLA antigens in immunoregulation will make it possible to interpret the phenomenon properly.

Influenza virus changes cell-surface glycoproteins including major histocompatibility complex determinants on lymphocytes

The effect of influenza virus infection on the expression of major histocompatibility complex (MHC) antigens was investigated. Infection with influenza virus resulted in an increase of the binding of anti-MHC class I and class II antibodies to resting T cells. The binding of anti-MHC class II antibodies to activated T cells was increased approximately threefold. The binding of anti-MHC class I and class II antibodies to Epstein-Barr virus-transformed B cells appeared unaffected after influenza virus infection. Recombinant human interferon-alpha and/or -gamma added to T cells did not enhance the binding of anti-MHC antibodies. Biochemical analysis revealed no increase in the amount of class I and class II antigens as a consequence of viral infection, but a marked decrease in sialic acid content was found, most probably caused by the viral neuraminidase. Pulse-chase experiments suggest that the viral neuraminidase can catalyze the removal of sialic acids both en route to and at the cell surface. The absence of sialic acid residues can explain the increased binding of anti-MHC antibodies, because neuraminidase (clostridium perfringens) treatment of T and Epstein-Barr virus-transformed B cells resulted in a shift in both isoelectric point and antibody binding similar to that observed after influenza virus infection.

Recombinant human tumor necrosis factor alpha suppresses autoimmune diabetes in nonobese diabetic mice

We previously reported that administration of a streptococcal preparation (OK-432) inhibited insulitis and development of autoimmune diabetes in nonobese diabetic (NOD) mice and BB rats as animals models of insulin-dependent diabetes mellitus. In this study, we screened various cytokines that could be induced by OK-432 in vivo, for their preventive effect against diabetes in NOD mice. Among recombinant mouse IFN gamma, human IL1 alpha, human IL2, mouse granulocyte-macrophage colony-stimulating factor and human TNF alpha, only human TNF alpha suppressed insulitis and significantly (P less than 0.001) inhibited development of diabetes. NOD mice were the lowest producers of the mRNA of TNF and serum TNF on stimulation with OK-432 or with IFN gamma plus LPS, compared with C57BL/6, C3H/He, and Balb/c mice. The results imply a role for low productivity of TNF in the pathogenesis of autoimmune diabetes in NOD mice.

Differential modulation by tumor necrosis factor and immune interferon of HLA class-II antigens expressed by melanoma cells

Tumor necrosis factor (TNF-alpha) was compared to immune interferon (IFN-gamma) for its ability to modulate the expression and shedding of HLA antigens, of intercellular adhesion molecule I (ICAM I) and of high-molecular-weight melanoma-associated antigen (HMW MAA) by a panel of melanoma cell lines. The latter included the melanoma cell line MeWo and its metastatic variant MeM 50-10, which display differential susceptibility to modulation of HLA class-II antigens by IFN-gamma and the cell lines SK-MEL-93-DX-2 and SK-MEL-93-DX-3, which originated from anatomically distinct metastases in patient DX. TNF-alpha enhanced the expression of HLA class-I antigens on all 7 melanoma cell lines tested, although to a lower extent than IFN-gamma and the combination of IFN-gamma and TNF-alpha. TNF-alpha displayed a differential effect on the expression of HLA class-II antigens by the 7 melanoma cell lines: it enhanced it on 3 out of the 4 cell lines with constitutive expression of HLA class-II antigens and induced them on 1 of 3 cell lines without detectable expression of these antigens. The effects of IFN-gamma were different since it enhanced HLA class-II antigens on the 4 cell lines with constitutive expression of these antigens and induced them on 2 out of the remaining 3 lines. Interestingly, both TNF-alpha and IFN-gamma enhanced the expression of HLA class-II antigens by SK-MEL-93-DX-3 cells. On the other hand only TNF-alpha induced the expression of HLA class-II antigens by MeWo cells and only IFN-gamma induced such expression by MeM 50-10 cells and by SK-MEL-93-DX-2 cells. The effect of the combination of TNF-alpha and IFN-gamma was similar to that of the individual cytokines. Both TNF-alpha and IFN-gamma displayed a differential effect on the expression of the gene products of the HLA-D region by the melanoma cell lines. Northern blot analysis with HLA-DR beta-, DQ beta- and DP beta-specific probes suggests that the modulation of HLA class-II antigens by both cytokines reflects transcriptional and post-transcriptional events. TNF-alpha enhanced the expression of ICAM-I on all the melanoma cell lines, although to a lower extent than IFN-gamma and the combination of IFN-gamma and TNF-alpha. Lastly, neither TNF-alpha nor IFN-gamma displayed a marked effect on the expression of HMW-MAA by the melanoma cell lines tested.

Chronic therapy with recombinant tumor necrosis factor-alpha in autoimmune NZB/NZW F1 mice

We studied the effects of recombinant murine tumor necrosis factor-alpha (TNF-alpha) on autoimmune disease in lupus-prone NZB/NZW F1 (B/W) mice. Treatment with TNF-alpha, begun after the onset of clinical disease, improved survival relative to control mice: at age 10 months, 92% of mice treated with TNF-alpha were alive compared with 42% of control mice (P less than 0.05). Administration of TNF-alpha delayed the progression of renal disease, but sustained therapy did not prevent the eventual development of severe nephritis. Despite the improvement in survival, treatment with TNF-alpha did not inhibit anti-dsDNA antibody production. However, it accelerated T lymphocytopenia and abolished natural killer cell activity. These observations suggest that TNF-alpha may retard murine lupus in B/W mice through effects on cellular rather than humoral mechanisms. Our findings also indicate that the beneficial effects of TNF-alpha cannot be sustained indefinitely by chronic therapy.

Immunotoxicology: suppressive and stimulatory effects of drugs and environmental chemicals on the immune system. A discussion

The fundamental characteristic of the adaptive immune system which has evolved in the vertebrates is the ability to recognise, and subsequently destroy, "foreign", and potentially harmful, antigens. The selective advantage which the immune system confers is the capacity to resist infectious, and possibly malignant, disease. It has been apparent for many years that individuals in whom immune function is impaired, due either to a congenital defect or to other factors such as treatment with certain immunosuppressive drugs, exhibit an increased susceptibility to infection and, in some cases, an elevated risk of developing at least some forms of malignancy. There is an increasing awareness from rodent studies that a variety of drugs and environmental chemicals have the potential to unintentionally impair components of the immune system. Risk assessment, based upon data from chemically induced changes in one or more parameters of immune function, is, however, dependent upon a knowledge of the functional reserve of the immune system. One of the objectives of the meeting from which this report derives was to examine what sources of information are available, and what experimental protocols can be employed, to permit accurate evaluation of immunological reserve. Although, under normal circumstances, the immune system selectively and specifically recognises foreign antigen, it is clear that the potential to recognise "self" is present and that in certain circumstances this potential is realised. Antibodies directed against normal tissue antigens have been shown to be associated with, and in some instances the presumptive cause of, "autoimmune" disease. There is a growing list of drugs and chemicals which are capable of eliciting autoantibodies and pathological autoimmune reactions. A second purpose of this meeting and of this report was to review the current state of knowledge regarding drug- and chemical-induced autoimmunity.

TNF-alpha gene polymorphisms in type 1 (insulin-dependent) diabetes mellitus

Type 1 (insulin-dependent) diabetes mellitus, like some other autoimmune diseases, is linked to certain alleles coded by genes in the HLA-D region. Sequence analysis of DQ beta chains indicates that aspartic acid at codon 57 confers resistance to the development of Type 1 diabetes. However, a full explanation for the HLA-association of Type 1 diabetes, particularly the increased susceptibility of DR3/4 heterozygotes is still awaited. The localisation of tumour necrosis factor genes on the short arm of chromosome 6 between HLA-B and the complement genes (Class III) prompted us to investigate a possible polymorphism of TNF-alpha at the genomic level in relation to Type 1 diabetes susceptibility. A dialleleic TNF-alpha restriction fragment length polymorphism was found with Ncol and its segregation with HLA-haplotypes analysed in diabetic families. We describe here a strong linkage of TNF-alpha alleles with certain DR haplotypes. For example, the common extended haplotype HLA A1-B8-DR3 was almost exclusively associated with the 5.5 kb TNF-alpha allele whereas Bw62-DR4 with the 10.5 kb allele. Thus both alleles segregate to diabetic patients. DR matched haplotypes of affected family members differed significantly from those of the non-affected at the TNF alpha locus. All affected sibling pairs in 11 multiplex affected families were identical for TNF-alpha alleles, even if they were only haploidentical for HLA-B-DR haplotypes. In addition, heterozygosity for the TNF-alpha alleles was significantly more frequent in the patients. This tight linkage of TNF-alpha alleles with some extended haplotypes could help to explain the HLA-association of Type 1 diabetes as well as some other autoimmune diseases.

Transgenic mice with I-A on islet cells are normoglycemic but immunologically intolerant

Insulin-dependent diabetes mellitus (IDDM) is caused by a specific loss of the insulin-producing beta cells from pancreatic Langerhans islets. It has been proposed that aberrant expression of major histocompatibility complex (MHC) class II molecules on these cells could be a triggering factor for their autoimmune destruction. This proposal was tested in transgenic mice that express allogeneic or syngeneic class II molecules on the surface of islet cells at a level comparable with that normally found on resting B lymphocytes. These animals do not develop diabetes, nor is lymphocyte infiltration of the islets observed. This immunological inactivity does not result from tolerance to the "foreign" class II molecules.