Distribution of interferon-gamma receptor in human tissues

Failure of exogenously administered interferon-gamma or blockage of endogenous interleukin-4 with specific inhibitors to augment the incidence of autoimmune diabetes in male NOD mice

Interferon (IFN)-gamma and interleukin (IL)-4 are prototypic type 1 and type 2 cytokines which are known to play pathogenetic and protective roles, respectively, in NOD mouse IDDM. The capacity of male NOD mice to produce more IL-4 and less IFN-gamma within the insulitic lesions than females has been suggested to contribute to their lower incidence of diabetes. In this study we have tested the effects of prolonged prophylactic treatment of male NOD mice with rat IFN-gamma, mouse IFN-gamma, anti-IL-4 monoclonal antibody (mAb) and recombinant murine soluble IL-4 receptor (smIL-4R) on the diabetogenic events leading to insulitis and diabetes. None of these treatments influenced spontaneous and/or cyclophosphamide-induced autoimmune diabetogenesis in male NOD mice. Control mice exhibited comparable histological signs of insulitis and incidence of diabetes to those treated with either mouse/rat IFN-gamma or specific IL-4 inhibitors. On the contrary, both clinical and histological signs of diabetes were suppressed by prophylactic treatment with anti-IFN-gamma mAb. These findings indicate that the autoimmune diathesis of male NOD mice towards IDDM cannot be augmented by manipulation of endogenous IFN-gamma or IL-4.

IFN-γ Mediates a Novel Antiviral Activity Through Dynamic Modulation of TRAIL and TRAIL Receptor Expression

TNF-related apoptosis-inducing ligand (TRAIL) is able to kill many transformed cells of diverse tissue types. We show that TRAIL is inducible by IFN-γ, by TNF-α, and by infection with human CMV, and has potent antiviral activity in vitro. CMV infection and IFN-γ also reciprocally modulate TRAIL receptor (TRAIL-R) expression. CMV infection increased the expression of TRAIL-R1 and -R2, whereas IFN-γ down-regulated the expression of TRAIL-Rs on uninfected fibroblasts. Moreover, IFN-γ significantly decreased the basal level of NF-κB activation, a known survival factor that inhibits apoptosis. Thus, TRAIL selectively kills virus-infected cells while leaving uninfected cells intact, and IFN-γ potentiates these effects by dynamic modulation of TRAIL and TRAIL-R expression and by sensitizing cells to apoptosis. The regulation of TRAIL and TRAIL-R expression may represent a general mechanism that contributes to the control of TRAIL-mediated apoptosis.

CD44, a cell surface chondroitin sulfate proteoglycan, mediates binding of interferon-gamma and some of its biological effects on human vascular smooth muscle cells

Several cytokines and growth factors act on cells after their association with the glycosaminoglycan (GAG) moiety of cell surface proteoglycans (PGs). Interferon-gamma (IFN-gamma) binds to GAG; however, the relevance of this interaction for the biological activity of IFN-gamma on human cells remains to be established. Human arterial smooth muscle cells (HASMC), the main cells synthesizing PG in the vascular wall, respond markedly to IFN-gamma. We found that treatment of HASMC with chondroitinase ABC, an enzyme that degrades chondroitin sulfate GAG, reduced IFN-gamma binding by more than 50%. This treatment increased the affinity of 125I-IFN-gamma for cells from a Kd value of about 93 nM to a Kd value of about 33 nM. However, the total binding was reduced from 9. 3 +/- 0.77 pmol/microg to 3.0 +/- 0.23 pmol/mg (n = 4). Interestingly, pretreatment with chondroitinase ABC reduced significantly the cellular response toward IFN-gamma. The interaction of IFN-gamma with chondroitin sulfate GAG was confirmed by affinity chromatography of isolated cell-associated 35S-, 3H-labeled PG on a column with immobilized IFN-gamma. The cell-associated PG that binds to IFN-gamma was a chondroitin sulfate PG (CSPG). This CSPG had a core protein of approximately 110 kDa that was recognized by anti-CD44 antibodies on Western blots. High molecular weight complexes between IFN-gamma and chondroitin 6-sulfate were observed in gel exclusion chromatography. Additions of chondroitin 6-sulfate to cultured HASMC antagonized the antiproliferative effect and expression of major histocompatibility complex II antigens induced by IFN-gamma. These results indicate that IFN-gamma binds with low affinity to the chondroitin sulfate GAG moiety of the cell surface CSPG receptor CD44. This interaction may increase the local concentration of IFN-gamma at the cell surface, thus facilitating its binding to high affinity receptors and modulating the ability of IFN-gamma to signal a cellular response.

Interferon consensus sequence-binding protein is constitutively expressed and differentially regulated in the ocular lens

Interferon signaling is mediated by STATs and interferon regulatory factor (IRF) families of transcription factors. Ten distinct IRFs have been described and most are expressed in a variety of cells except for interferon consensus sequence-binding protein (ICSBP) and lymphoid-specific IRF/Pip that are thought to be exclusively expressed in lymphoid cells. We show here for the first time that ICSBP is constitutively and inducibly expressed in the mouse lens. In contrast to lymphoid cells with exclusive expression of ICSBP in the nucleus, ICSBP is present in both the cytoplasm and nucleus of the lens cell. However, ICSBP in the nucleus is of lower apparent molecular weight. We further show that the ICSBP promoter is constitutively bound by lens nuclear factors and that its activation requires binding of additional factors including STAT1. Furthermore, transcriptional activation of ICSBP gene by interferon gamma is accompanied by selective nuclear localization of ICSBP in proliferating epithelial cells but not in the nuclei of nondividing cells in the lens fiber compartment. Constitutive and inducible expression of ICSBP in the ocular lens and differential regulation of its subcellular localization in the developing lens suggest that ICSBP may have nonimmunity related functions and that the commonly held view that it is lymphoid-specific be modified.

Comparative effects of cytokines on constitutive and inducible expression of the gene encoding for the cytochrome P450 3A6 isoenzyme in cultured rabbit hepatocytes: consequences on progesterone 6beta-hydroxylation

Cultured rabbit hepatocytes were used to compare the relative activities of cytokines to inhibit the constitutive or rifampicin (RIF)-induced expression of the cytochrome P450 3A6 gene (CYP3A6). Human recombinant cytokines tested were interleukin-1beta (IL-1beta) (2 U/mL), interleukin-2 (IL-2) (5,000 U/mL) and interferon-gamma (IFN-gamma) (50 U/mL). Hepatocytes were cultured in the presence or absence of 25 microM RIF for 24 hr, with or without cytokines alone or in combination. All these cytokines inhibited RIF-induced P4503A6 expression without apparent cellular toxicity. By contrast, only IFN-gamma treatment provided a significant decrease (41%) in the constitutive P4503A6 protein level. Moreover, cytokines differed in their ability to repress RIF-dependent transcriptional induction of CYP3A6: IL-1beta and IL-2 were approximately equipotent, causing an almost 40-50% suppression of CYP3A6 mRNA and protein levels, whereas IFN-gamma exerted repressive effects only on P4503A6-related erythromycin N-demethylase activity and inducible protein expression. In fact, although strongly reducing P4503A6 protein content (an approximate 70% decrease), IFN-gamma did not exhibit any influence on CYP3A6 mRNAs with the exception of its association with interleukins. All these results suggest that IL-1beta and IL-2 mainly promote a transcriptional repression mechanism, given the absence of effect of these cytokines on the basal P4503A6 level, whereas IFN-gamma exerts a post-transcriptional suppressive action on both induced and constitutive P4503A6 expression. Consequently, P4503A6-dependent progesterone 6beta-hydroxylase activity also presented a cytokine-specific pattern of inhibition, with a much greater sensitivity than P4503A6 immunoreactive protein to IL-1beta and IL-2 + IFN-gamma treatments. Thus, this study underlines the significant impact of inflammation on steroid metabolism.

Expression of MHC class I and beta2-microglobulin in rat spinal motoneurons: regulatory influences by IFN-gamma and axotomy

The low expression of MHC antigens is believed to be one factor of importance contributing to the immune-privileged status of CNS neurons. We here describe that motoneurons, in contrast to other nerve cells in the lumbar spinal cord of the adult rat, express both MHC class I and beta2-microglobulin mRNA. The motoneurons also display in situ hybridization signal for IFN-gamma receptor mRNA. After a peripheral axotomy, the motoneurons show a clear upregulation of beta2-microglobulin mRNA. IFN-gamma treatment of cultured rat embryonic spinal motoneurons causes a similar upregulation of especially beta2-microglobulin. Based on these facts, we propose that spinal motoneurons can be influenced by IFN-gamma and recognized by cytotoxic CD8+ T-cells. These findings could be of relevance in the search for pathogenetic mechanisms in motoneuron-specific diseases, such as ALS.

Interferon-gamma-induced JAK2 and STAT1 signalling in a human salivary gland cell line

We have used a human salivary gland cell line (HSG) as a possible in vitro model to evaluate the effects of IFN-gamma on human salivary gland epithelium (Wu et al., 1994, 1996, 1997). In the present study, we examined the JAK-STAT signal-transduction pathway in IFN-gamma-treated HSG cells. We demonstrate that JAK2 and Stat1 are phosphorylated at tyrosine residues in a time- and concentration-dependent manner following exposure to IFN-gamma. In addition, we show that activation of this signalling pathway is decreased by the addition of a blocking antibody to the IFN-gamma receptor. The same maneuver is also able to reduce by approximately 50-70% the surface expression of two IFN-gamma-induced immunoregulatory molecules: HLA-DR and ICAM-1. These results demonstrate that the JAK2 and Stat1 signalling pathway is active in salivary-derived epithelial cells and may contribute to their immunopathologic destruction.

The interferon gamma (IFN-gamma) receptor: a paradigm for the multichain cytokine receptor

With the purification and cloning of the interferon gamma (IFN-gamma) receptor chains the mechanism of IFN-gamma action and the resultant signal transduction events were delineated in remarkable detail. The interferon gamma (IFN-gamma) receptor complex consists of two chains: IFN-gammaR1, the ligand-binding chain, and IFN-gammaR2, the accessory chain. Binding of IFN-gamma causes oligomerization of the two IFN-gamma receptor subunits, IFN-gammaR1 and IFN-gammaR2, which initiates the signal transduction events: activation of Jak1 and Jak2 receptor associated protein tyrosine kinases, phosphorylation of the IFN-gammaR1 intracellular domain on Tyr440 followed by phosphorylation and activation of Stat1alpha, the latent transcriptional factor. With all these steps established, the IFN-gamma receptor complex has provided the basic model for understanding the receptors for other members of the family of class II cytokine receptors.

Gut intraepithelial lymphocytes induce immunity against Cryptosporidium infection through a mechanism involving gamma interferon production

Immunological control of infection with cryptosporidia in mice is dependent on CD4+ T cells and the production of gamma interferon (IFN-gamma), but to date, the mucosal T cells which produce IFN-gamma local to the infection have not been characterized. We previously showed that immunity against the gastric parasite Cryptosporidium muris could be adoptively transferred to adult SCID (severe combined immunodeficiency) mice with small intestinal intraepithelial lymphocytes (IEL) from previously infected immunocompetent mice, but only if the donor CD4+ T cells were intact. The present investigation examined whether IFN-gamma was important in the effector mechanisms mediated by immune IEL in SCID mice. The development of resistance against C. muris infection in SCID mice given immune IEL was prevented by treatment with a hamster anti-mouse IFN-gamma-neutralizing monoclonal antibody, but following cessation of antibody treatment, the mice recovered from infection. In further experiments, an enzyme-linked immunospot (ELISPOT) technique was used to compare frequencies of IFN-gamma-producing cells in activated T-cell populations from C. muris-immune and naive donor mice. Stimulation with concanavalin A or a rat anti-mouse CD3 monoclonal antibody resulted in detection of greater numbers of cells producing IFN-gamma from immune than naive IEL populations. Small numbers of IEL from C. muris-immune mice, but not from naive mice, also produced IFN-gamma when cultured with soluble oocyst antigen, but this occurred only if gamma-irradiated spleen cells were cocultured with the immune IEL. These results suggested that IEL were important in the generation of immunity to Cryptosporidium and that one of their crucial functions was to produce IFN-gamma at the site of infection.

Tumor necrosis factor-beta in human pregnancy and labor

The aims of this study were to determine tumor necrosis factor-beta (TNF-beta) concentration profiles in peripheral venous plasma and amniotic fluid during pregnancy and at the time of labor and to characterise TNF-beta mRNA expression and TNF-beta release from human gestational tissues. In addition, we investigated the expression of TNF-beta binding protein, lymphotoxin-beta (LT-beta), in human gestational tissues. The mean (+/-S.E.M.) TNF-beta concentrations in maternal plasma (TIL, 78 +/- 12 pg/ml, n = 7 vs. TNIL, 304 +/- 88 pg/ml, n = 7) and amniotic fluid (TIL, 8 +/- 5 pg/ml, n = 6 vs. TNIL, 73 +/- 20 pg/ml, n = 20) were significantly (P < 0.05) decreased in association with term labor-onset (TIL) compared to term not-in-labor (TNIL). TNF-beta concentration in maternal plasma and amniotic fluid did not change significantly either with preterm labor (PIL), or during pregnancy. Group-matched comparison of maternal plasma and amniotic fluid TNF-beta concentrations demonstrated that amniotic fluid TNF-beta concentrations were 6-8 fold lower than maternal plasma TNF-beta concentrations. Furthermore, no detectable TNF-beta was secreted from cultured human amniotic, choriodecidual and placental explants. Although, TNF-beta mRNA was detected in amnion, choriodecidual and placenta, LT-beta was similarly expressed in these tissues, suggesting that TNF-beta may be cell membrane bound. These data demonstrate that TNF-beta is present at low levels within the intrauterine environment and may suggest that TNF-beta is specifically inhibited at the maternal-fetal interface.

CRF2-4: isolation of cDNA clones encoding the human and mouse proteins

To search for genes which encode human interferon receptor molecules, we applied the technique of exon trapping to human chromosome 21 yeast artificial chromosomes (YACs). A full length cDNA encoding human CRF2-4 was identified which is shown here to be widely expressed in human tissues. The human CRF2-4 cDNA was used as a probe to screen a mouse macrophage cDNA library. A mouse CRF2-4 cDNA was isolated which encodes a 349-amino-acid (aa) polypeptide that is 69% identical at the aa level with its human counterpart. Mouse CRF2-4 is predicted to be another member of the interferon receptor-class II cytokine receptor family.

Cellular responses to interferon-gamma

Interferons are cytokines that play a complex and central role in the resistance of mammalian hosts to pathogens. Type I interferon (IFN-alpha and IFN-beta) is secreted by virus-infected cells. Immune, type II, or gamma-interferon (IFN-gamma) is secreted by thymus-derived (T) cells under certain conditions of activation and by natural killer (NK) cells. Although originally defined as an agent with direct antiviral activity, the properties of IFN-gamma include regulation of several aspects of the immune response, stimulation of bactericidal activity of phagocytes, stimulation of antigen presentation through class I and class II major histocompatibility complex (MHC) molecules, orchestration of leukocyte-endothelium interactions, effects on cell proliferation and apoptosis, as well as the stimulation and repression of a variety of genes whose functional significance remains obscure. The implementation of such a variety of effects by a single cytokine is achieved by complex patterns of cell-specific gene regulation: Several IFN-gamma-regulated genes are themselves components of transcription factors. The IFN-gamma response is itself regulated by interaction with responses to other cytokines including IFN-alpha/beta, TNF-alpha, and IL-4. Over 200 genes are now known to be regulated by IFN-gamma and they are listed in a World Wide Web document that accompanies this review. However, much of the cellular response to IFN-gamma can be described in terms of a set of integrated molecular programs underlying well-defined physiological systems, for example the induction of efficient antigen processing for MHC-mediated antigen presentation, which play clearly defined roles in pathogen resistance. A promising approach to the complexity of the IFN-gamma response is to extend the analysis of the less understood IFN-gamma-regulated genes in terms of molecular programs functional in pathogen resistance.

T-lymphocyte immunointerferon receptors in patients with multiple sclerosis

Multiple sclerosis (MS) is a T-cell-mediated autoimmune demyelinating disease of the central nervous system (CNS), associated with an altered immunoregulation. Interferon (IFN)-gamma, also known as immune IFN, is a cytokine with several effects on the immune system. Specific IFN-gamma receptors have been found on human lymphocytes, as well as on other cell types (e.g. gliocytes), even in the CNS. The aim of the present study was to evaluate IFN-gamma binding on peripheral blood T-lymphocytes from MS patients, compared with those from healthy subjects. Thirty-two patients were selected according to the classical criteria for definite MS; as controls, 21 healthy subjects were studied. We have found that T-lymphocytes from MS patients bear a significantly smaller amount of IFN-gamma receptors than those from controls [Bmax: 568, 18 vs 708, 14 (mean, SE) receptors/ cell]. Such IFN-gamma binding sites are of the same type in patients and healthy subjects [Kd: 1.0, 0.05 vs 0.9, 0.02 (mean, SE) nM]. These findings are discussed in terms of immunopathogenesis of MS, since it has been reported that activated T-lymphocytes have decreased amounts of IFN-gamma receptors.

Interferon-gamma induced cell death in a cultured human salivary gland cell line

Increased levels of several cytokines, including interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), have been demonstrated in the salivary gland microenvironment of patients with Sjögren's syndrome (SS). How these cytokines may be contributing to the pathogenesis of the disease is not well understood. This study examined the role of IFN-gamma +/- TNF-alpha on cellular death in a cultured human salivary gland cell line (HSG). Cells treated long-term with IFN-gamma +/- TNF-alpha demonstrate a profound antiproliferative effect with a decrease in cell number to below that initially plated. Treatment of HSG cells with TNF-alpha alone did not have any significant effects on growth but did increase the expression of the IFN-gamma receptor. Cells labelled with propidium iodide and anti-digoxigenin dUTP/dATP were examined by flow cytometry to determine the percentage of cells exhibiting low DNA content and DNA strand breaks. The percentage of cells exhibiting subdiploid DNA and DNA strand breaks increased with increased time of exposure to the cytokines. The maximum percentage of cells exhibiting DNA degradation at 12 days was 58% for cells treated with IFN-gamma + TNF-alpha, 31% for IFN-gamma treated cells, and < 5% for TNF-alpha-treated and untreated cells. The cells with subdiploid ( < 2n) DNA were subsequently demonstrated to represent two populations, both with evidence of increased DNA strand breaks but with differing light scatter characteristics. One population had features of cells undergoing necrosis, whereas the second population exhibited features of apoptosis. These findings were confirmed by transmission electron microscopy. Cells not exposed to cytokines did not exhibit significant evidence of either death process. We conclude that long-term exposure of a human salivary gland epithelial cell line to IFN-gamma +/- TNF-alpha leads to increased DNA degradation and subsequent cell death. This suggests a potential SS disease mechanism and implicates the role of the epithelial cell in this disease as an important area for future study.

The interleukin-2 receptor down-regulates the expression of cytochrome P450 in cultured rat hepatocytes

BACKGROUND & AIMS

Interleukin (IL) 2 is used in advanced cancers, but its effects on cytochrome P450 remain unknown. Other cytokines down-regulate hepatic cytochrome P450, but it is not known whether this involves cytokine receptors. The aim of this study was to determine whether the IL-2 receptor is expressed on hepatocytes and whether its activation by IL-2 depresses cytochrome P450 in cultured rat hepatocytes.

METHODS

A monoclonal antibody specific for the rat IL-2 receptor alpha chain was used to label the receptor, whereas effects on cytochrome P450 were determined after 24 hours of culture with human recombinant IL-2 (5000 U/mL).

RESULTS

The presence of the IL-2 receptor in hepatocytes was shown by immunoblots, flow cytometry, and scanning confocal microscopy. IL-2 caused a 46% decrease in total cytochrome P450; a 35%, 35%, 36%, 26%, and 56% decrease in immunoreactive cytochrome P4501A1, 2B, 2C11, 2D1, and 3A, respectively; and a marked decrease in cytochrome P4503A2 and 2C11 messenger RNAs. Addition to the culture medium of the anti-receptor antibody or the tyrosine kinase inhibitor genistein prevented the IL-2-mediated decrease in cytochrome P450.

CONCLUSIONS

IL-2 down-regulates the expression of cytochrome P450 genes in cultured rat hepatocytes by interacting with its receptor expressed on hepatocytes.

Distribution of interferon-gamma receptors in normal and psoriatic skin

Recent data suggest that imbalances in production and secretion of cytokines, in particular interferon-gamma (IFN-gamma), may be crucial in the pathogenesis of psoriasis. In order to exert its role on target cells, IFN-gamma has to interact with a specific cell membrane receptor termed the IFN-gamma-receptor (IFN-gamma R). We studied the distribution of IFN-gamma Rs in frozen skin biopsies from 25 psoriatics and 5 normal controls with two unrelated monoclonal antibodies, and compared its distribution with that of the IFN-gamma-inducible HLADR- and ICAM-1 antigens. In normal skin, IFN-gamma Rs were restricted to the basal cell layer; weak staining was found on scattered mononuclear cells in the papillary dermis. In 13/25 active psoriatic lesions, additional suprabasal immunoreactive foci, and in 5/25 cases, diffuse immunoreactivity of the entire epidermis were seen. No striking topographical similarities between the site and number of IFN-gamma R+, HLADR+ and ICAM-1+ keratinocyte foci were observed, suggesting that cytokines other than IFN-gamma induce HLADR-antigens on psoriatic keratinocytes in vivo. The restricted distribution of IFN-gamma R on the germinative cell layer in normal skin confirms the role played by IFN-gamma in the normal growth regulation of the epidermis. The de novo suprabasal expression of IFN-gamma R in psoriasis argues against the current hypothesis that IFN-gamma R are down-regulated due to a local excess of IFN-gamma or transforming growth factor alpha (TGF-alpha). Whether IFN-gamma Rs in psoriatic skin are functionally normal and involved in signal transmission, remains to be studied.

Critical influences of the cytokine orchestration on the outcome of myelin antigen-specific T-cell autoimmunity in experimental autoimmune encephalomyelitis and multiple sclerosis

In EAE/MS, effector molecules are produced as a result of the interaction between T lymphocytes and antigen-presenting cells and the spectrum of cytokines produced is likely to decisively influence the disease outcome. These events may be more important, or at least more easily accessible to therapeutic intervention, than particular autoantigen specificities. Data from EAE suggest that cytokines connected to the Th1 phenotype of lymphocytes, especially IFN-gamma but also TNF-beta, TNF-alpha and IL-12, may promote inflammation while cytokines connected to the Th2 subset, IL-4, IL-10 and TGF-beta, may potentially have a role in disease limitation. It will be important to accurately study cytokines during immunotherapeutic interventions and in relation to immunogenetic variables in order to aim at immunotherapeutically intervening in the Th1, Th2 balance as well as counteracting disease-promoting cytokines such as IFN-gamma and TNF-alpha or promoting the action of downregulatory cytokines such as IL-10 and TGF-beta.

Interferon gamma receptor extracellular domain expressed as IgG fusion protein in Chinese hamster ovary cells. Purification, biochemical characterization, and stoichiometry of binding

Agents that antagonize the functions of interferon gamma (IFN gamma) are potential pharmaceuticals against several immunological and inflammatory disorders. IFN gamma receptor-immunoglobulin G fusion proteins (IFN gamma R-IgG) function as antagonists of endogenous IFN gamma and have longer half-lives in vivo in comparison with soluble IFN gamma receptors (sIFN gamma R), consisting of the extracellular region of the native sequence. A fusion protein comprising the extracellular domain of the human IFN gamma receptor and the hinge, CH2 and CH3 domains of the human IgG3 constant region, was expressed in Chinese hamster ovary cells. The IFN gamma R-IgG3 fusion protein was secreted into the culture medium as a 175-kDa glycoprotein and was purified over Protein G-Sepharose, DEAE-Sepharose, and size exclusion chromatography. IFN gamma R-IgG3 bound IFN gamma in solid phase assays and ligand blots, competed for the binding of radiolabeled IFN gamma to the cell surface receptor of Raji cells, and inhibited the IFN gamma-mediated antiviral activity with an efficiency at least one order of magnitude higher than that of the soluble receptor produced in the same expression system. Two IFN gamma R-IgG3 fusion proteins bound two IFN gamma dimers forming a complex of approximately 380 kDa. In immunodiffusion assays, the IFN gamma R-IgG3 fusion protein did not precipitate IFN gamma. Dissociation of bound IFN gamma from IFN gamma R-IgG3 was 2-fold slower than from the sIFN gamma R produced in insect cells.

Suppression of interferon-gamma induction of MHC class II and ICAM-1 by a 26-base oligonucleotide composed of deoxyguanosine and deoxythymidine

Interferon-gamma (IFN-gamma) is an important cytokine released by T lymphocytes and natural killer cells which is able to induce expression of class II MHC and ICAM-1, crucial factors in cellular immune response. HeLa S3, HS 27, and NF-71-1 are cell lines which can be induced to express HLA-DR and HLA-DP by exposure to IFN-gamma. When T2 (5'GGGGTTGGTTGTGTTGGGTGTTGTGTRNH(2)3') oligonucleotide was added at 5-20 microM every other day, cell surface induction of HLA-DR and HLA-DP by IFN-gamma was suppressed in a dose-dependent manner in HeLa S3. T2 suppressive effect on HLA class II was also observed in four different nontransformed human cell lines, HS 27 at passage 18, NF-71-1 at passage 5, human corneal endothelial cell at passage 5, and human retinal pigmented epithelial cell at passage 3. Control oligonucleotides had no suppressive effect. Northern hybridization showed that HLA-DR A mRNA induction by IFN-gamma was blocked by T2 in HeLa S3 and fibroblast 143B. The suppressive effect of T2 was also reversible as continued culture of the treated cells without further addition of the oligonucleotide allowed full re-expression of HLA-DR. Further experiments showed that T2 oligonucleotide was also able to inhibit IFN-gamma enhancement of ICAM-1 (CD54) on human corneal endothelial cell and human retinal pigmented epithelial cell. We conclude that T2 oligonucleotide is effective at suppressing HLA-DR, HLA-DP and ICAM-1 induction by IFN-gamma in transformed and nontransformed cells in vitro.

Cytotoxicity of tumour necrosis factor-alpha and gamma-interferon against primary human placental trophoblasts

Tumour necrosis factor-alpha (TNF-alpha) and gamma interferon (IFN-gamma) are expressed within human placental villi during normal pregnancy, yet their functions remain unknown. Since villous cytotrophoblasts are within the paracrine reach of this expression, the effects of TNF-alpha and IFN-gamma on a purified population of term placental cytotrophoblasts were examined. After 4 days of culture TNF-alpha alone induced a loss of trophoblast viability as measured by both metabolic capacity (MTT reduction) and DNA content. The combination of TNF-alpha and IFN-gamma enhanced the damaging effect. Neutralizing antibodies against TNF receptor p55, but not p75, partially reversed the TNF-alpha-induced cytotoxicity. After 24 h of culture, TNF-alpha and IFN-gamma increased the fraction trophoblasts containing nicked DNA, and after 60 h, increased the detachment of cells characterized by a distorted morphology, lower DNA content, and fragmented DNA. These results suggest that a physiological role of TNF-alpha and IFN-gamma expression in the placental villi may be to regulate the apoptotic death of villous cytotrophoblasts. The studies also predict potential harmful effects on placental development and function following aberrant inflammatory cytokine expression triggered by intravillous infections.

Effect of tumor necrosis factor-alpha and interferon-gamma on the growth of a human salivary gland cell line

Interferon-gamma (IFN-gamma) is a product of activated T-lymphocytes, and tumor necrosis factor-alpha (TNF-alpha) is a product of both lymphocytes and macrophages. These cell types are often present at sites of tissue damage secondary to chronic infection or autoimmune disease. The purpose of this study was to characterize the effects of TNF-alpha and IFN-gamma on a human submandibular gland epithelial cell line (HSG). IFN-gamma caused a concentration-dependent decrease in HSG cell growth (approximately 70% in 6 days). Conversely, TNF-alpha alone had little effect on the growth of these cells. When these cytokines were added in combination (20 units/ml TNF-alpha and 1,000 units/ml of IFN-gamma), there was a synergistic antiproliferative effect; no apparent cell growth was observed. The cytokine-induced antiproliferative effect was reversible. After the apparent cessation of cell growth for 3-6 days, removal of the cytokines permitted complete growth recovery. Further, cells that recovered and exhibited growth patterns that were similar to control cells remained susceptible to the antiproliferative effects of the cytokines. Flow cytometry revealed that the percentage of cells in G0/G1 with the combination of cytokines was significantly increased by 24 h. The antiproliferative effect of IFN-gamma alone and that of IFN-gamma and TNF-alpha in combination were blocked completely using an antibody to the IFN-gamma receptor. A hypothesized mechanism of tissue damage in autoimmune inflammatory disorders is via up-regulation of cell surface markers such as intercellular adhesion molecule type I (ICAM-1) and histocompatibility antigen HLA-DR which can exacerbate the inflammatory process. Treatment of HSG cells with IFN-gamma, with or without TNF-alpha, resulted in increased levels of ICAM-1 and the acquisition of HLA-DR expression. These aggregate data suggest that IFN-gamma alone can regulate the expression of cell surface markers involved in the inflammatory process as well as cause a potent yet reversible inhibition of HSG cell growth that is modulated by the presence of TNF-alpha.

First trimester human trophoblast expresses both interferon-gamma and interferon-gamma-receptor

Interferon-gamma (IFN-gamma) is a lymphokine, produced by activated T lymphocytes, which plays a key regulatory role in the host immunological responses. In addition, IFN-gamma is expressed by human and porcine trophoblast. As IFN-gamma exerts its biological functions through specific cell surface receptors and a great number of IFN-gamma receptors (IFN-gamma R) have been purified from human placenta, we have examined the relative distribution of IFN-gamma and IFN-gamma R in human placental tissues at different stages of pregnancy. By using immunohistochemical analysis and monoclonal antibodies, it was found that IFN-gamma expression is intense in the first trimester but almost imperceptible at term, whereas the expression of IFN-gamma R is present at both stages of pregnancy. For both lymphokine and receptor, the most intense expression was observed in villous syncytiotrophoblast and in extravillous interstitial trophoblast. From these results it appears that the expression of IFN-gamma R in trophoblast is related to the presence of the lymphokine in the early phase of gestation but not later. On this basis, it can be argued that IFN-gamma exerts its functional role via an autocrine and/or a paracrine loop mainly during the first trimester.

Mechanisms of innate and acquired resistance to Cryptosporidium parvum infection in SCID mice

SCID mice, which lack T and B cells, were used as hosts to investigate the nature of both T cell-independent and T-cell-dependent immune responses to infection with Cryptosporidium parvum. We found previously that SCID mice developed chronic infections in which the level of oocyst excretion was low up to about eight weeks post-infection but then increased significantly to cause morbidity and death after 13 weeks. In the present study, weekly administration of an anti-IFN-gamma monoclonal antibody (MoAb) resulted in a shortened prepatent time, significant increase in oocyst excretion and early onset of disease and death. These results suggested an immunologically mediated resistance to C. parvum in the SCID host which required the production of IFN-gamma. Attempts to demonstrate a role for TNF in nonspecific immunity were unsuccessful as injection of mice at weekly intervals with an anti-TNF MoAb failed to alter the course of infection. In contrast to the chronic infection observed in the mice above, SCID mice reconstituted with spleen cells from naive BALB/c mice were able to recover. Depletion of CD4+ cells from the donor population abrogated this protective effect. Mice receiving spleen cells depleted of CD8+ cells were able to recover but the patent infection was prolonged compared with those obtained in mice receiving unfractionated cells. These results demonstrate that CD4+ cells are necessary for the development of immunity to C. parvum infection in reconstituted SCID mice, but, in addition, that CD8+ cells also make a significant contribution to this immunity.

Which steps in lymphocyte recirculation are regulated by interferon-gamma?

Lymphocyte traffic throughout the body is a basic mechanism of immune surveillance. Most studies of the regulation of the extravasation of lymphocytes have focused on the interaction between endothelial cells of the high endothelial venules (HEV) in lymphoid organs and lymphocytes via the interaction of various adhesion molecules. Cytokines play a major role in the regulation of immune reactions, and some have been shown to upregulate adhesion molecules important for lymphocyte migration. Using interferon-gamma (IFN gamma) as an example of such a cytokine, we summarize the available data on regulation by IFN gamma of the different phases of lymphocyte migration from the blood via HEV, through the lymphoid organ and finally exiting the organ. Much data obtained in in vitro assays have not yet been confirmed in vivo, and therefore a number of questions remain unanswered. Our hypothesis is that the interaction of lymphocytes with endothelial cells represents just one aspect of regulation, and that lymphocyte migration is probably regulated much more effectively within the lymphoid organ.

Anti-tumor necrosis factor modulates anti-CD3-triggered T cell cytokine gene expression in vivo

De novo expression of TNF, IFN gamma, IL-3, IL-4, and IL-6 genes was initiated rapidly by treatment of mice with anti-CD3. A specific feature of this reaction was that TNF was derived exclusively from T cells. TNF was produced both as a mature soluble trimeric protein and as a 26-kD anti-TNF-reactive protein compatible with membrane-anchored TNF. Pretreatment with anti-TNF did not affect anti-CD3-triggered TNF mRNA expression in T cells. In contrast, in vivo and in vitro anti-TNF treatment upregulated anti-CD3-induced IFN gamma mRNA expression and inhibited IL-4 mRNA expression. These latter effects were not dependent on TNF neutralization: pretreatment with soluble recombinant 55-kD TNF receptor (TBPI) as an alternative TNF-neutralizing agent did not modify the anti-CD3-induced cytokine profile. These results suggest that a direct interaction between anti-TNF and T cell membrane-anchored TNF could account for the observed modulation of cytokine gene expression. The increased expression of INF gamma mRNA observed in anti-TNF-treated animals correlated with a decrease in IL-3 and IL-6 mRNA expression. Conversely, IFN gamma blockade by a neutralizing anti-IFN gamma mAb led to a substantial increase in both IL-3 and IL-6 gene expression induced by anti-CD3. Taken together, these results strongly argue for the existence, in the anti-CD3-induced cytokine cascade, of IFN gamma-dependent regulation of IL-3 production, which in turn modulates IL-6 production.

Cytokine activity after allogeneic bone marrow transplantation. V. Analysis of IL-2 and IFN production by isolated CD4+ and CD8+ cells

Previous studies from this laboratory have shown that PBMC from recipients of an HLA-identical sibling bone marrow transplant produce levels of IL-2 which are 10-100-fold lower than those produced by the same number of PBMC from healthy controls, whereas production of IFN-gamma is normal. The present study examined IL-2 and IFN production over a range of cell numbers for PBMC and for isolated CD4+ and CD8+ cells for controls and marrow transplant recipients. There was a 5-fold lower IL-2 production in marrow transplant recipient CD8+ cells compared with equivalent numbers of control cells, whereas no difference was found in IL-2 production by CD4+ cells. In contrast, IFN production by CD4+ cells from marrow transplant recipients was 4-fold higher than in controls, whereas CD8+ cells from both populations produced similar amounts of IFN. When the observed production of cytokine by PBMC was compared with the expected production based on the CD4+ and CD8+ content of the PBMC, control values were similar, but the expected values for both cytokines were approximately 2-fold higher than the observed values for marrow transplant recipients. The results suggest that the capacity of T cells from marrow transplant recipients to produce IL-2 and IFN is not impaired, but that the frequency of cytokine-producing cells may be reduced, and that a negative interaction present in recipient PBMC, eliminated by isolating T-cell subsets, is responsible for the observed low levels of cytokine production.

Expression of the interferon-gamma receptor gene in mouse placentas is related to stage of gestation and is restricted to specific subpopulations of trophoblast cells

In order to evaluate the potential of placental cells to bind the multifunctional cytokine, interferon-gamma (IFN-gamma), tissues collected from pregnant Swiss mice were analysed for IFN-gamma receptor (IFN-gamma R) mRNA and protein. Northern blot hybridization studies indicated that the relative abundance of IFN-gamma R mRNA increased as gestation progressed to term. Analysis by in situ hybridization revealed that trophoblast cells first contained high steady state levels of IFN-gamma R mRNA at g.d. 12. At g.d. 12 and 14, transcription was restricted to cells in the spongiotrophoblast region and nests of similar cells in the labyrinthine region. These cells also contained immunoreactive IFN-gamma R protein. By g.d. 18, IFN-gamma R mRNA was clearly detectable in large spongiotrophoblast cells and labyrinthine trophoblast. IFN-gamma R mRNA was low to absent in giant trophoblast cells at all stages of gestation. Specific mRNA was present in parietal and visceral yolk sac cells by g.d. 14. Thus, expression of the IFN-gamma R gene in mouse placental cells is influenced by stage of gestation, cell lineage and state of differentiation. Whether or not these cells respond vigorously to IFN-gamma with induction of antiviral proteins, increased MHC class I antigens and growth modulation may therefore be determined by their expression of specific receptors for this pluripotent cytokine.

Gamma interferon functions in resistance to Cryptosporidium parvum infection in severe combined immunodeficient mice

Severe combined immunodeficient (SCID) adult mice are relatively resistant to Cryptosporidium parvum infection, even though they are deficient in both T- and B-cell function. The requirement for gamma interferon (IFN-gamma) in this resistance was examined by treatment of these mice with monoclonal antibody to IFN-gamma. SCID mice injected intraperitoneally with monoclonal anti-IFN-gamma 4 h before and three times weekly after challenge with C. parvum had heavy intestinal infections 3 weeks postchallenge. SCID mice similarly injected with irrelevant antibody were not infected. Furthermore, SCID mice receiving a single injection of anti-IFN-gamma either 2 h before or 18 h after challenge were also susceptible to infection. Although IFN-gamma was not detected in SCID mouse intestinal samples, it was found in the supernatant of SCID mouse splenocyte cultures after stimulation with C. parvum antigens. On the other hand, SCID mice receiving multiple injections of antibodies against tumor necrosis factor remained resistant to infection. These data indicate that the resistance of SCID mice to C. parvum infection is IFN-gamma dependent, whereas tumor necrosis factor appears not to play a significant role.

Modulation of interferon-gamma receptor during human T lymphocyte alloactivation

Previous work has shown that neutralization of physiologically secreted interferon(IFN)-gamma or blockade of its receptor during T lymphocyte activation inhibits both proliferation and cytotoxic T lymphocyte generation, suggesting that IFN-gamma plays a crucial role in T lymphocyte induction and differentiation. In this study, the kinetics of the surface expression of the 90-kDa IFN-gamma receptor (IFN-gamma R) was followed during human mixed lymphocyte reaction (MLR) to alloantigens. IFN-gamma R mRNA is constitutively expressed on resting peripheral blood lymphocytes emerging from nylon wood column (NW-PBL) and its expression increases two- to threefold on alloactivated NW-PBL. IFN-gamma R protein is poorly expressed on the membrane of resting CD3+ cells, but up-modulates after 3-day MLR and sharply down-modulates at day 6. Both the p55 and the p75 chains of interleukin-2 receptor (IL-2R) were shown to up-modulate in parallel with IFN-gamma R, whereas they were still highly expressed at day 6. After alloactivation, IFN-gamma and IL-2 secretion starts at 24 h, peaks at day 3 and decreases just when IFN-gamma R and IL-2R begin to up-modulate. Proliferation peaks at day 6. Lastly, stimulation with distinct cell populations showed that the intensity of lymphocyte proliferation, IFN-gamma R membrane up-modulation, and IFN-gamma and IL-2 secretion are regulated in a parallel manner, thus suggesting that they are interrelated. Taken as whole these results demonstrate that increased expression of IFN-gamma R on T lymphocytes can be a critical event during their activation, and strongly support the hypothesis that IFN-gamma/IFN-gamma R interaction provides a signal for its progression.

Immune response in mice that lack the interferon-gamma receptor

Interferon-gamma (IFN-gamma) exerts pleiotropic effects, including antiviral activity, stimulation of macrophages and natural killer cells, and increased expression of major histocompatibility complex antigens. Mice without the IFN-gamma receptor had no overt anomalies, and their immune system appeared to develop normally. However, mutant mice had a defective natural resistance, they had increased susceptibility to infection by Listeria monocytogenes and vaccinia virus despite normal cytotoxic and T helper cell responses. Immunoglobulin isotype analysis revealed that IFN-gamma is necessary for a normal antigen-specific immunoglobulin G2a response. These mutant mice offer the possibility for the further elucidation of IFN-gamma-mediated functions by transgenic cell- or tissue-specific reconstitution of a functional receptor.

Prevention of cyclophosphamide-induced diabetes in the NOD/WEHI mouse with deoxyspergualin

Ten out of 20 (50%) 17-week-old female NOD/WEHI mice developed an acute form of autoimmune diabetes when injected with two large doses of cyclophosphamide (CY), given at 14-day intervals. If these mice were treated under a prophylactic regimen with 2.5 mg/kg body weight per day of the novel immunosuppressant deoxyspergualin (DSP) the onset of diabetes was completely prevented. Moreover, DSP-treated animals showed reduced signs of pancreatic insulitis, had lower percentages of splenic lymphoid cells (SLC) expressing IL-2 receptors and Ly-6C antigens on their surfaces, and these cells released lower amounts of interferon-gamma (IFN) when stimulated in vitro. These data, providing evidence for the capacity of DSP to protect NOD/WEHI mice from experimental autoimmune diabetes and to modulate histo-immunological pathogenic pathways, indicate DSP as a drug of potential interest in the treatment of human insulin-dependent diabetes mellitus.

Immunomodulation with soluble IFN-gamma receptor: preliminary study

Several in vivo experiments support the hypothesis that an IFN-gamma antagonist may have therapeutic applications in autoimmune diseases, hypersensitivities, and alloreactions. IFN-gamma exerts its biological activity through the binding to a single-chain cell surface receptor. The protein that corresponds to the external domain of mouse IFN-gamma receptor was expressed in insect cells infected with recombinant baculovirus; this protein was characterized and used in vivo as a prototype of the IFN-gamma antagonist. This protein does not show any strong antigenicity after in vivo injection in mice. Despite a blood half-life of only 1-3 hr as demonstrated in pharmacokinetic experiments, the mouse soluble IFN-gamma R was able to modify the onset of acute GVHD (alloreaction) and chronic GVHD (lupuslike disease).