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Results for “Interleukin-12 Subunit p40”

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At least 19 recordsLinked to original sources

PubMed1993

The interleukin-12 subunit p40 specifically inhibits effects of the interleukin-12 heterodimer.

The recently discovered cytokine interleukin (IL)-12 is a heterodimeric protein of two disulfide-bonded subunits of 35 and 40 kDa. IL-12 has multiple effects on T cells and natural killer (NK) cells. In particular it appears to be a major factor for the development of cellular immunity. So far activity of the single subunits alone has not been described, however their expression is regulated independently. In this report we demonstrate for the first time that the mouse IL-12 subunit p40 (IL-12p40) specifically antagonizes the effects of the IL-12 heterodimer in different assay systems. The proliferation of mouse splenocytes activated by phorbol ester and IL-12 was inhibited by IL-12p40, whereas the proliferation induced by phorbol ester and IL-2 was not affected. Furthermore, the synthesis of interferon (IFN)-gamma by mouse splenocytes activated with IL-2 and IL-12 was suppressed by IL-12p40. Purified mouse splenic CD4+ T cells produced IFN-gamma upon activation with plate-bound anti-CD3 monoclonal antibody which was enhanced more than tenfold in the presence of IL-12. In this system IL-12p40 inhibited only the enhancement caused by IL-12 but not IFN-gamma synthesis of CD4+ T cells stimulated with anti-CD3 alone. Moreover, IL-12p40 inhibited the effects of IL-12 on differentiated T helper type 1 (Th1) cells. IFN-gamma production by Th1 cells induced in a T cell receptor-independent way by macrophages and IL-2 or macrophages and IL-12 was greatly reduced by IL-12p40 providing evidence for the endogenous synthesis of IL-12 in the Th1 cell, macrophage and IL-2 co-cultures. The specificity of inhibition was clearly demonstrated in the homotypic aggregation assay of Th1 cells. Incubation of Th1 cells with either IL-2 and IL-12 or IL-2 and tumor necrosis factor induces LFA-1/ICAM-1-dependent aggregation. Only IL-2 + IL-12 but not IL-2 + tumor necrosis factor-induced aggregation was inhibited in a dose-dependent manner by IL-12p40. Thus, the IL-12 subunit p40 appears to be a specific inhibitor for the IL-12 heterodimer.

Animals↗

PubMed1994

Differential expression of mRNA encoding interleukin-12 p35 and p40 subunits in situ.

Interleukin-12 (IL-12) is a heterodimeric cytokine that plays an important role in the regulation of the immune response. For biological activity the expression of both subunits of IL-12, p35 and p40, is required. Moreover, in the mouse the p40 chain of IL-12 specifically inhibits the effects of the IL-12 heterodimer. In the present study we have analyzed by in situ hybridization the expression of the p35 and p40 mRNA in the spleens of BALB/c and mutant (SCID, nude, beige) mice, unstimulated and after in vivo stimulation with lipopolysaccharide (LPS) and with staphylococcal enterotoxin B (SEB). In unstimulated spleens of BALB/c mice p35 and p40 mRNA were only detectable in a few strongly stained single cells, p35 mRNA was expressed in addition weakly in the B cell areas. After injection of LPS or SEB, p40 mRNA was strongly induced in the T cell areas all over the spleen, whereas expression of p35 mRNA and its distribution pattern did not change. Surprisingly, most of the mRNA for p35 and p40 was localized in different areas of the spleen and was apparently produced by different cells. In macrophage-depleted spleens the increased expression of p40 mRNA in response to LPS was reduced but still detectable, demonstrating that other cells besides macrophages can up-regulate IL-12 p40 mRNA. Nude mice showed a stronger expression of p35 mRNA, SCID mice lacked the weak p35 staining of the B cell areas but showed a strong basal expression of both p35 and p40 mRNA and a focal response to LPS. The pattern of IL-12 mRNA expression in beige mice was the same as in normal mice. These data demonstrate a spatial dissociation of expression of the two chains of IL-12 and are compatible with a regulatory role of the isolated IL-12 p40 chain in vivo. In addition, they indicate that the demonstration of mRNA for both chains of IL-12 in whole tissues or cell mixtures is not necessarily indicative of functional IL-12.

Animals↗

PubMed1996

A novel interleukin-12 p40-related protein induced by latent Epstein-Barr virus infection in B lymphocytes.

We have isolated a cDNA encoding a novel hematopoietin receptor family member related to the p40 subunit of interleukin-12 and to the ciliary neurotrophic factor receptor, whose expression is induced in B lymphocytes by Epstein-Barr virus (EBV) infection. This gene, which we have designated EBV-induced gene 3 (EBI3), encodes a 34-kDa glycoprotein which lacks a membrane-anchoring motif and is secreted. Despite the absence of a membrane-anchoring motif and of cysteines likely to mediate covalent linkage to an integral membrane protein, EBI3 is also present on the plasma membrane of EBV-transformed B lymphocytes and of transfected cells. Most newly synthesized EBI3 is retained in the endoplasmic reticulum in an endoglycosidase H-sensitive form associated with the molecular chaperone calnexin and with a novel 60-kDa protein. EBI3 is expressed in vivo by scattered cells in interfollicular zones of tonsil tissue, by cells associated with sinusoids in perifollicular areas of spleen tissue, and at very high levels by placental syncytiotrophoblasts. EBI3 expression in vitro is induced in EBV-negative cell lines by expression of the EBV latent infection membrane protein-1 and in peripheral blood mononuclear cells by pokeweed mitogen stimulation. EBI3 maps to chromosome 19p13.2/3, near genes encoding the erythropoietin receptor and the cytokine receptor-associated kinase, Tyk2. EBI3 synthesis by trophoblasts and by EBV-transformed cells and similarities to interleukin-12 p40 are compatible with a role for EBI3 in regulating cell-mediated immune responses.

Amino Acid Sequence↗

PubMed2026

Exploring Causal Links Between 91 Circulating Inflammatory Proteins and Hashimoto's Thyroiditis: A Bidirectional Mendelian Randomization Study.

BACKGROUND: Increasing evidence has linked inflammation to Hashimoto's thyroiditis (HT) etiology. However, the causal role of circulating inflammatory proteins in HT remains uncertain. To investigate this, we conducted a bidirectional Mendelian randomization (MR) study. METHODS: Genetic data for 91 inflammatory proteins and HT were sourced from publicly available GWAS databases. The PhenoScanner database was then searched for pleiotropic SNPs associated with potential confounders. Inverse variance weighted (IVW) analysis was used as the primary analysis, simultaneously supplemented by five sensitivity analyses to strengthen the results. RESULTS: The results revealed that, after false discovery rate (FDR) correction, interleukin (IL)-12p40 was causally associated with increased risk of HT (OR [95% CI] = 1.295 [1.172, 1.431], p = 3.66 × 10-7, PFDR = 3.33×10-5). Conversely, none of the inflammatory proteins was a consequence of HT. CONCLUSION: This study suggests that IL-12p40 is probably one of the factors correlated with HT etiology, contributing to a better understanding of the pathogenesis of HT and underscoring the potential for therapeutic interventions targeting inflammatory proteins.

Humans↗

PubMed1995

High cytokine production and effective antitumor activity of a recombinant vaccinia virus encoding murine interleukin 12.

We have constructed a recombinant vaccinia virus (recVV), vKT0334 mIL-12, containing the genes encoding the p35 and p40 subunits of murine interleukin-12 (mIL-12). In vitro experiments demonstrated that vKT0334 mIL-12 efficiently infected a variety of murine and human tumor cell lines and produced very high amounts (1.5 micrograms/10(6) cells/24 h) of biologically active mIL-12. Mice injected s.c. with 10(6) MCA 105 sarcoma cells, followed by injection at the same site with saline or a control recVV, vKT033, containing no mIL-12 genes, all developed progressively growing tumor, whereas 60% of animals injected with vKT0334 mIL-12 remained tumor free (P < 0.0005). Furthermore, tumor growth was significantly reduced in the remaining mice treated with vKT0334 mIL-12 that did develop tumor compared with mice treated with vKT033 (P < 0.03) or saline (P < 0.0001). We conclude that recVV expressing high levels of mIL-12 offers an effective in vivo method of cytokine gene delivery and expression in tumors with subsequent antitumor effect.

Animals↗

PubMed1992

Assignment of genes encoding a unique cytokine (IL12) composed of two unrelated subunits to chromosomes 3 and 5.

IL12 (formerly NKSF or CLMF) is a unique cytokine composed of two unrelated disulfide-linked subunits. The larger 40-kDa subunit (p40) is a member of the cytokine receptor family, and the smaller 35-kDa subunit (p35) is related to IL6 and GCSF. The chromosomal localization of these two subunits was determined by PCR analysis of DNA from rodent-human hybrids. More refined mapping was obtained by PCR analysis of hybrids containing translocation chromosomes and for p40, by analysis of radiation hybrids. The subunits map to different chromosomes: p40 (IL12B) to 5q31-q33 and p35 (IL12A) to 3p12-3q13.2.

Animals↗

PubMed1995

Human IL-12 p40 homodimer binds to the IL-12 receptor but does not mediate biologic activity.

IL-12, a heterodimeric cytokine, consists of two disulfide-linked subunits, p40 and p35. We investigated the role of p40 in ligand binding and signal transduction by expressing this subunit alone in COS cells. Culture media of the transfected COS cells exhibited specific dose-dependent binding to KIT225/K6 cells, a human T cell line that expresses IL-12R. Analysis of the culture media by SDS-PAGE and Western blotting demonstrated the presence of 40-kDa monomers and 80-kDa disulfide-linked homodimers. The two p40 species were purified and identified by N-terminal sequencing and proteolytic peptide mapping. Characterization of the p40 proteins for binding and bioactivity showed that both the p40 monomer and dimer inhibited 125I-labeled IL-12 binding to IL-12R, but the 80-kDa species, having a 50% inhibitory concentration (IC50) of 20 to 70 ng/ml, was at least 20-fold more effective than the monomer. Although neither the monomer nor the dimer stimulated human PHA-blast proliferation, the 80-kDa dimer inhibited IL-12-induced proliferation in a dose-dependent manner with an IC50 of 65 ng/ml. The results suggest that the IL-12 p40 subunit contains the essential epitopes for receptor binding. However, a proper conformation required for high affinity binding is achieved only when p40 is associated with a p35 subunit or another p40 subunit. When p40 is associated with a p35 subunit, the heterodimer acts as an agonist mediating biologic activity. However, when p40 associates with another p40, the homodimer behaves as an antagonist in vitro.

Animals↗

PubMed1995

In vivo induction of interleukin-12 mRNA expression after oral immunization with Salmonella dublin or the B subunit of Escherichia coli heat-labile enterotoxin.

Mice orally immunized with Salmonella dublin EL23, a nonreverting, aromatic-dependent, histidine-requiring mutant transformed with a plasmid which carries a gene that codes for production of the B subunit of the heat-labile toxin (LT-B) of enterotoxigenic Escherichia coli, or with purified LT-B alone were compared for their ability to initiate expression of interleukin-12 (IL-12) mRNAs at mucosal sites. At 6 or 20 h following oral immunization, the Peyer's patches and mesenteric lymph nodes were removed, and polyadenylated mRNA was prepared from each tissue. Constitutive expression of an mRNA encoding the p35 subunit of IL-12 was observed in control as well as immunized mice. Conversely, expression of an mRNA encoding the p40 subunit of IL-12 was not detected in control animals but was dramatically upregulated in immunized mice. By using semiquantitative reverse transcription-PCR (RT-PCR) followed by competitive RT-PCR, differences in the magnitude of IL-12 p40 mRNA expression were quantified. Six hours after oral immunization with the Salmonella construct, mice had 12.1- and 8.4-fold increases in expression of IL-12 p40 mRNA in the Peyer's patches and mesenteric lymph nodes, respectively, compared with control mice receiving only saline. By 20 h, the pattern of increased mRNA expression was reversed, showing 2.5- and 17.6-fold increases in the Peyer's patches and mesenteric lymph nodes, respectively. Oral immunization with LT-B alone also stimulated IL-12 p40 mRNA expression, but to a lesser extent. The constitutive expression of IL-12 p35 mRNA at these mucosal sites coupled with a rapid and dramatic induction of IL-12 p40 mRNA following immunization with wild-type or attenuated strains of S. dublin is consistent with other investigations which support a role for IL-12 in modulating cell-mediated immune responses against intracellular pathogens.

Administration, Oral↗

PubMed1995

Interleukin-12 expression in human lymphomas and nonneoplastic lymphoid disorders.

Interleukin-12 (IL-12), a cytokine with in vitro and in vivo immunomodulatory effects, is produced by lymphocytes and stimulated monocytes. Little is known about the production and possible role of IL-12 in human lymphoproliferative disorders. We examined IL-12 expression by immunohistochemistry using antibodies recognizing the p40, p35 subunits, and the p70 heterodimeric IL-12 protein, and by Northern blot in lymph nodes from patients with Hodgkin's disease (HD), non-Hodgkin's lymphomas (NHL), and nonneoplastic lymphoid lesions. In the majority of the HD cases (28 of 34), IL-12 immunoreaction was found in small lymphoid cells cultured around Hodgkin and Reed-Sternberg (H&RS) cells. No IL-12 signal was seen in H&RS cells. Transcripts for IL-12 were found by Northern and dot blot analysis in 13 of 19 (IL-12 p40) and 11 of 19 (IL-12 p35) cases. The HD cases were further examined for the presence of Epstein-Barr virus (EBV) latent membrane protein (LMP-1). All cases with EBV-LMP-1 positivity (22 of 34 cases) also expressed IL-12. No IL-12 immunoreaction was found in neoplastic cells of 33 cases of various NHLs, which were all LMP-1 negative and showed no EBV-genome sequence, as assessed by polymerase chain reaction (PCR). In 24 nonneoplastic lymphoid lesions, few dispersed IL-12 positive cells were seen in the parafollicular area and in the sinus of the lymph node. The marked presence of IL-12 in the majority of HD cases indicates that IL-12 might play a role in the pathobiology of HD, suggesting that this cytokine is involved in EBV-positive HD.

Biomarkers↗

PubMed1995

Administration of systemic or local interleukin-2 enhances the anti-tumor effects of interleukin-12 gene therapy.

Interleukin-12 (IL-12) is a cytokine with a wide variety of immunoregulatory activities. These include stimulation of interferon-gamma production, cytolytic activity of natural killer (NK) cells and T-cell subsets, the development of cellular immunity, and induction of maturation of Th1 cells. IL-12 also has potent anti-tumor activity in vivo. In the present study the possibility of enhanced anti-tumor activity was examined using a combination of local IL-12 by cytokine gene therapy at the tumor site, combined with systemic or local IL-2 delivery. NIH 3T3 fibroblasts transfected with the genes for both subunits of IL-12, p35 and p40, were used as the source of IL-12 therapy producing 240 HLRU/10(6) cells/48 hr. In the first part of the study the effect of different regimens of systemic IL-2 delivery with local IL-12 administration on the size and growth rate of subcutaneous MCA-105 murine sarcoma was examined. Local IL-12 alone reduced the sizes of tumors after 32 days from 163 to 26.8 mm2 (P < 0.002). Adding the longer-acting polyethylene-glycol-modified IL-2 (PEG IL-2; 30,000 IU) for 5 days prevented the development of tumors in all treated mice compared to 1/3 mice treated with PEG IL-2 alone and 3/6 mice with IL-12, but this was a highly toxic therapy and most of the animals died. Administration of 60,000 IU of IL-2 on Days 1-5 postinoculation of tumor, delivered with IL-12 gene therapy, reduced the tumor growth rate compared to animals treated with IL-2 alone (P < 0.02) or IL-12 (0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

3T3 Cells↗

PubMed1991

Cloning of cDNA for natural killer cell stimulatory factor, a heterodimeric cytokine with multiple biologic effects on T and natural killer cells.

Previously we have reported the purification and characterization of a novel cytokine from an EBV-transformed B cell line, RPMI 8866. This factor, termed natural killer cell stimulatory factor (NKSF), possessed pleiotropic activities including the induction of IFN-gamma from PBL, enhancement of cytotoxicity by NK cells, and stimulation of the proliferation of PBL. Purified NKSF was found to be a disulfide-linked heterodimeric protein composed of 35-kDa and 40-kDa subunits (p35 and p40). We now report the molecular cloning of cDNA for both subunits of NKSF from RPMI 8866 cellular RNA. The cDNA sequences indicate that both genes are novel, and Southern blot analysis confirmed that both cDNA are of human genomic origin. [35S]Methionine labeling indicated that cos-1 cells transfected with either p35 or p40 cDNA produced unique protein species of appropriate size. Methionine labeling of cos-1 cells cotransfected with p35 plus p40 cDNA yielded a broad band migrating between 70 and 90 kDa on a nonreducing gel. Reduction of this high molecular weight material yielded bands correlating with p35 and p40 gene products. Only culture supernatant from cotransfected cos-1 cells had a high level of NKSF biologic activity. That the high molecular weight material was responsible for this activity was indicated by the observation that biologic activity in the culture supernatant migrated at 70 to 90 kDa in a nonreducing gel. Furthermore, anti-p40 serum was able to block the biologic activities of both recombinant and natural NKSF, which indicates that it is a component of the active protein. In contrast, no activity could be detected in the supernatants of cos-1 cells transfected with p40 or p35 cDNA alone. The spectrum of biologic activity produced by cotransfected cos-1 cells was the same as NKSF purified to homogeneity from the RPMI 8866 cell line. A synergistic augmentation of some of these responses was found by the addition of IL-2 or the co-stimulators PHA or phorbol diester. The synergistic stimulation by NKSF plus IL-2 of T and NK function supports the possibility that these cytokines might prove useful in cancer therapy.

Amino Acid Sequence↗

PubMed1995

Mouse interleukin-12 (IL-12) p40 homodimer: a potent IL-12 antagonist.

Interleukin-12 (IL-12) is a cytokine that has regulatory effects on T and natural killer (NK) cells and is composed of two disulfide-bonded subunits, p40 and p35. It was recently reported that supernatants from cultures of mouse IL-12 (moIL-12) p40-transfected COS cells could inhibit IL-12-dependent responses in vitro (Mattner, F., et al., Eur. J. Immunol. 1993. 23: 2202). We have further characterized the nature of the inhibitory substance. Purified mouse p40 produced in a baculovirus expression system was found to consist of two species: the p40 monomer and a disulfide-linked p40 dimer [(p40)2]. The (p40)2 was 25- to 50-fold more active than the p40 monomer in causing specific, dose-dependent inhibition of IL-12-induced mouse concanavalin A (Con A) blast proliferation and could also inhibit IL-12-induced interferon-gamma (IFN-gamma) secretion by mouse splenocytes and IL-12-dependent activation of mouse NK cells. Competitive binding studies on mouse Con A blasts showed that (p40)2 was equally effective as moIL-12 in competing with 125I-labeled moIL-12 ([125I]moIL-12) for binding to mouse Con A blasts. However, in contrast to moIL-12, mouse (p40)2 displayed little ability to compete with 125I-labeled human IL-12 (huIL-12) for binding to high-affinity IL-12 receptors (IL-12R) on human phytohemagglutinin (PHA) blasts and caused little or no inhibition of huIL-12-induced human PHA blast proliferation. Nonetheless, mouse (p40)2 was equally effective as moIL-12 in competing with [125I] huIL-12 for binding to COS cells transfected with the human IL-12R beta subunit and expressing low-affinity IL-12 binding sites. These results suggest that (i) the majority of the structural determinants required for binding of IL-12 to its receptor are contained within the p40 subunit, but p35 is required for signaling, (ii) the p40 subunit of IL-12 interacts with the beta subunit of IL-12R, and (iii) (p40)2 may be a suitable IL-12 antagonist for studying the role of IL-12 in various immune responses in vivo as well as in vitro. Further studies are required to determine whether or not (p40)2 is produced by normal lymphoid cells and is a physiologic regulator of IL-12 activity.

Animals↗

PubMed1994

Interleukin 12 is produced in vivo during endotoxemia and stimulates synthesis of gamma interferon.

Gamma interferon (IFN-gamma) is produced in response to circulating lipopolysaccharide (LPS) and contributes to the lethality of endotoxic shock. To address the cellular source of IFN-gamma production in vivo, T cells and B cells were magnetically purified from C57BL/6 mouse spleens 5 h following endotoxin injection. IFN-gamma RNA was abundant in splenic CD4+ and CD8+ T cells and in a T- and B-cell-depleted population of splenocytes containing 34% NK1.1+ natural killer (NK) cells. Because interleukin 12 (IL-12) is a known inducer of IFN-gamma synthesis by cultured T cells and NK cells, we examined whether IL-12 might be involved in IFN-gamma release during endotoxemia. mRNA encoding the p40 subunit of IL-12 increased markedly in the spleens of C57BL/6 mice at 2 h after LPS injection, whereas p35 IL-12 mRNA was constitutively expressed at all times. Bioactive IL-12 (p70 heterodimer) was detected in mouse serum at 2 to 4 h after LPS injection. Similar results were obtained using a p40 subunit-specific enzyme-linked immunosorbent assay. Endotoxin-insensitive C3H/HeJ mice generated threefold less IL-12 p70 and IFN-gamma at these times than endotoxin-sensitive C3H/HeOuJ mice. Pretreatment of mice with polyclonal anti-mouse IL-12 antibody reduced IFN-gamma levels present at 6 h post-LPS nearly sixfold in three separate experiments. These studies support a role for IL-12 as a proximal stimulator of IFN-gamma release during endotoxemia.

Animals↗

PubMed1995

Regulation of interleukin 12 p40 expression through an NF-kappa B half-site.

Interleukin 12 (IL-12) is an inducible cytokine composed of 35- and 40-kDa subunits that is critical for promoting T helper type 1 development and cell-mediated immunity against pathogens. The 40-kDa subunit, expressed by activated macrophages and B cells, is induced by several pathogens in vivo and in vitro and is augmented or inhibited by gamma interferon (IFN-gamma) or IL-10, respectively. Control of IL-12 p40 expression is therefore important for understanding resistance and susceptibility to a variety of pathogens, including Leishmania major and perhaps human immunodeficiency virus. In this report, we provide the first characterization of IL-12 p40 gene regulation in macrophages. We localize inducible activity of the promoter to the sequence -122GGGGAATTTTA-132 not previously recognized to bind Rel family transcription factors. We demonstrate binding of this sequence to NF-kappa B (p50/p65 and p50/c-Rel) complexes in macrophages activated by several p40-inducing pathogens and provide functional data to support a role for NF-kappa B family members in IL-12 p40 activation. Finally, we find that IFN-gamma treatment of cells enhances this binding interaction, thus potentially providing a mechanism for IFN-gamma augmentation of IL-12 production by macrophages.

Animals↗

PubMed1992

Cloning and expression of murine IL-12.

Human IL-12 (NK cell stimulatory factor, cytotoxic lymphocyte maturation factor) is a heterodimeric cytokine that can act as a growth factor for activated human T and NK cells, enhance the lytic activity of human NK/lymphokine-activated killer cells, and stimulate the production of IFN-gamma by resting human PBMC. Because in our hands, human IL-12 did not elicit similar responses in murine lymphocytes, we have cloned and expressed the murine IL-12 subunit cDNA in order to obtain recombinant protein for murine studies. Comparison of the predicted amino acid sequences of the murine subunits with their human counterparts revealed that the p40 subunits are more highly conserved than the p35 subunits (70% vs 60% identity, respectively). The sizes of the p35 and p40 subunit mRNA were estimated to be 1.5 kb and 2.6 kb, respectively. RNA blot analysis showed that p35 mRNA was expressed in lymphoid tissues (spleen, thymus) and nonlymphoid tissues (lung, brain), whereas p40 mRNA expression was only detected in lymphoid cells. Incubation of splenocytes with pokeweed mitogen did not significantly affect p35 mRNA levels, however, it resulted in a decrease of p40 mRNA. Coexpression of the murine p35 and p40 cDNA clones in COS cells resulted in the secretion of IL-12, which was active in human and mouse T cell proliferation, murine NK cell activation, and murine IFN-gamma induction assays. Transfection of each subunit cDNA alone did not result in measurable secreted IL-12 activity. A hybrid heterodimer consisting of murine p35 and human p40 subunits retained bioactivity on murine cells; however, the combination of human p35 and murine p40 was completely inactive on murine cells. These results indicate that the observed inability of human IL-12 to act on murine cells is largely determined by the p35 subunit.

Amino Acid Sequence↗

PubMed1994

IL-12 is expressed and released by human keratinocytes and epidermoid carcinoma cell lines.

IL-12 is a 70-kDa heterodimeric cytokine composed of two covalently linked chains, p40 and p35. IL-12 has multiple effects on T and NK cells and recently was found to be required for optimal Th1 cell development. In a variety of inflammatory skin disorders including delayed type hypersensitivity and contact hypersensitivity, Th1 cells appear to be critically involved. Because keratinocytes are well known to exhibit the capacity to release a variety of proinflammatory and immunologic cytokines, and thereby to be able to modulate inflammatory and immune reactions within the skin, it was investigated whether human keratinocytes and keratinocyte cell lines can release IL-12. Supernatants of phorbol-12,13-dibutyrate (PDBu) stimulated human epidermoid carcinoma cell lines (KB, A431) induced IFN-gamma production by PBL. This activity could be completely blocked by the addition of an anti-IL-12 Ab directed against the p40 subunit of IL-12 (C8.6). Release of IL-12 by keratinocyte cell lines was further confirmed by an RIA specific for p40. Immunoprecipitation under reducing conditions using the C8.6 Ab yielded specific bands at 40 kDa in supernatants of both KB cells and normal human keratinocytes. Northern blot analysis revealed IL-12-specific mRNA transcripts in PDBu-treated KB cells using cDNA probes encoding for p35 and p40. Moreover, by reverse transcription PCR specific transcripts for p35 and p40 were found in keratinocytes. These data indicate that keratinocyte cell lines and, although to a much lesser degree, normal human keratinocytes, exhibit the capacity to make IL-12; thus demonstrating for the first time IL-12 production by nonhemopoietic cells. Thus, one may speculate that keratinocytes via this capacity may influence the fate of Th-mediated immune responses, favoring Th1 responses by enhanced production of IL-12 or Th2 responses by reduced IL-12 release.

Base Sequence↗

PubMed1995

Dendritic cells produce IL-12 and direct the development of Th1 cells from naive CD4+ T cells.

Dendritic cells are APCs that are unique in their potency to stimulate proliferation of primary Ag-specific responses in vitro and in vivo. In this study, we demonstrate that dendritic cells can produce IL-12, a dominant cytokine involved in the development of IFN-gamma-producing T cells. This finding resulted from our observations that dendritic cell-induced Th1 development from total CD4+ T cells upon neutralization of endogenous levels of IL-4 was IL-12-dependent. Furthermore, we demonstrate that dendritic cells can induce the development of Th1 cells from Ag-specific naive LECAM-1bright CD4+ T cells obtained from alpha beta-TCR transgenic mice, provided that CD4+ LECAM-1dull T cells, which produce significant levels of IL-4, are not present in the primary cultures. Production of IL-12 by dendritic cells was confirmed by positive immunofluoresence staining with Abs specific for the inducible IL-12 p40 subunit. This suggests that in addition to inducing proliferation and clonal expansion of naive T cells, dendritic cells, by their production of IL-12, play a direct role in the development of IFN-gamma-producing cells that are important for cell-mediated immune responses.

Animals↗

PubMed1995

Effective eradication of established murine tumors with IL-12 gene therapy using a polycistronic retroviral vector.

Our recent studies using IL-12 protein or fibroblasts genetically engineered to secrete IL-12 have demonstrated profound antitumor effects of IL-12 in murine models. The antitumor effects of local, high level IL-12 expression were examined using a retroviral vector, which can express both IL-12 subunits (p35 and p40) and the neomycin phosphotransferase (Neo)-marker gene from a polycistronic message utilizing internal ribosome entry site sequences. All animals intradermally (i.d.) receiving MCA207 murine sarcoma cell line nontransfected or Neo-transfected had progressively growing tumor, whereas all animals injected with MCA207 transfected with IL-12 were tumor free and were subsequently determined to be immune to a rechallenge of nontransfected MCA207 i.d. Similar results were obtained in experiments using the poorly immunogenic MCA102 murine sarcoma cell line. The inoculation of live MCA207-IL-12 tumor cells also caused the regression of contralateral nontransfected MCA207 inoculated either at the same time (80% protection) or up to 3 days before (33% protection) to the therapeutic tumor inoculation. In vivo depletion studies suggest that NK cells and IFN-gamma play important roles in the development of the early phase of the antitumor response, but that T cells (both CD4+ and CD8+) play the major role in the subsequent events, leading to long-term immunity. The potent antitumor effects observed for paracrine gene-delivered administration of IL-12 have thus been confirmed for multiple tumor cell types and in multiple murine strains. We believe that these results support the feasibility of IL-12 gene therapy for the treatment of human cancer.

Animals↗