Proinflammatory and immunoregulatory functions of interleukin-12

Recombinant bovine interleukin-12 stimulates a gut immune response but does not provide resistance to Cryptosporidium parvum infection in neonatal calves

This study was undertaken to determine if administration of recombinant bovine interleukin-12 (rBoIL-12) could stimulate a cellular immune response that protected calves from an oral challenge inoculation with Cryptosporidium parvum oocysts. In a first experiment, rBoIL-12 intraperitoneally administered as a single dose 1 day before challenge inoculation, did not alter the course of infection. The percentage of immune competent cells and levels of cytokine gene expression in the ileo-cecal mucosa and in the draining lymph nodes of treated calves were similar to those of untreated control calves. However, when rBoIL-12 was subcutaneously administered daily from 2 days before infection to 2 days after infection, a consistent increase of T lymphocytes and an higher expression of interferon-gamma (IFN-gamma) was detected. Again, treatment did not alter the course of infection. Similar results were obtained when rBoIL-12 was administered daily for 4 days beginning 2 days after oral inoculation. These data indicate that although rBoIL-12 stimulated a strong immune response in the gut of neonatal calves, the response was not able to provide protection from challenge inoculation with C. parvum oocysts.

The Novel Cytokine p43 Induces IL-12 Production in Macrophages via NF-κB Activation, Leading to Enhanced IFN-γ Production in CD4+ T Cells

Recently, we determined that p43, an auxiliary factor of mammalian multiaminoacyl-tRNA synthetases, is secreted, and functions as a novel pleiotropic cytokine. In this study, we have attempted to characterize the effects of p43 on the generation of IL-12 in mouse macrophages. p43 was determined to induce significant IL-12 production from mouse macrophages in a dose-dependent manner. The stimulatory effect of p43 on the activation of IL-12p40 promoter was mapped to a region harboring an NF-kappaB binding site. The nuclear extracts from the p43-stimulated macrophages exhibited profound NF-kappaB DNA-binding activity, as determined by the EMSA. In addition, the p43-stimulated IL-12 induction and NF-kappaB DNA-binding activity were significantly suppressed by caffeic acid phenethyl ester and BAY11-7082, both inhibitors of NF-kappaB activation, indicating that p43 induced the production of IL-12 in macrophages mainly via the activation of NF-kappaB. Importantly, p43 increased the level of IFN-gamma production in the Ag-primed lymph node cells, but had no effect on IL-4 levels. The addition of a neutralizing anti-IL-12p40 mAb to the cell cultures resulted in a decrease of the production of p43-enhanced IFN-gamma by the keyhole limpet hemocyanin-primed lymph node cells. Furthermore, coincubation with p43-pretreated macrophages enhanced the production of IFN-gamma by the keyhole limpet hemocyanin-primed CD4+ T cells, thereby indicating that p43 may enhance IFN-gamma expression in CD4+ T cells via the induction of IL-12 production in macrophages. These results indicate that p43 may play an essential role in the development of the Th1 immune responses associated with cancer immunotherapy and protective immunity against intracellular pathogens.

Virulizin, a novel immunotherapy agent, activates NK cells through induction of IL-12 expression in macrophages

Virulizin, a novel biological response modifier, has demonstrated significant antitumor efficacy in a variety of human tumor xenograft models including melanoma, pancreatic cancer, breast cancer, ovarian cancer and prostate cancer. The significant role of macrophages and NK (Natural killer) cells was implicated in the antitumor mechanism of Virulizin where expansion as well as increased activity of macrophages and NK cells were observed in mice treated with Virulizin. Depletion of macrophages compromised Virulizin-induced NK1.1+ cell infiltration into xenografted tumors and was accompanied by reduced antitumor efficacy. In the present study, involvement of macrophages in NK cell activation was investigated further. We found that depletion of NK cells in CD-1 nude mice by anti-ASGM1 antibody significantly compromised the antitumor activity of Virulizin. Cytotoxicity of NK cells isolated from Virulizin-treated mice was enhanced against NK-sensitive YAC-1 cells and C8161 human melanoma cells, but not against NK-insensitive P815 cells. An increased level of IL-12beta was observed in the serum of mice treated with Virulizin. IL-12 mRNA and protein levels were also increased in peritoneal macrophages isolated from Virulizin-treated mice. Moreover, Virulizin-induced cytotoxic activity of NK cells isolated from the spleen was abolished when an IL-12 neutralizing antibody was co-administered. In addition, depletion of macrophages in mice significantly impaired Virulizin-induced NK cell cytotoxicty. Taken together, the results suggest that Virulizin induces macrophage IL-12 production, which in turn stimulates NK cell-mediated antitumor activity.

A dose sparing effect by plasmid encoded IL-12 adjuvant on a SIVgag-plasmid DNA vaccine in rhesus macaques

An experimental pDNA vaccine adjuvant expressing IL-12 was evaluated for its ability to augment the humoral and cellular immune responses elicited by a SIVmac239 gag p39 expressing pDNA vaccine. To determine the effect of vaccine dose on the immune response, rhesus macaques were immunized with 1.5 mg or 5.0 mg of SIVmac239 gag pDNA, with or without co-immunization of IL-12 pDNA at 1.5 mg and 5.0 mg, respectively. Serum antibody responses to simian immunodeficiency virus (SIV) gag were increased 10-fold (p=0.044, 0.002) in macaques receiving IL-12 pDNA. Cellular immune responses, monitored by SIV gag-specific IFN-gamma ELISpot assay, were also significantly higher (p=0.007, 0.019) when the pDNA vaccine was co-immunized with IL-12 pDNA at high and low doses. There was no statistical difference between the immune responses elicited by the high and low dose of IL-12 pDNA (p=0.221, 0.917), a finding which could allow a dose reduction of vaccine without the concomitant loss of imunogenicity. Furthermore, analysis of the breadth of the T-cell response during the vaccination schedule, using overlapping peptides to SIV gag, demonstrated a significant correlation (p=0.0002) between the magnitude and breadth of the immune responses in the vaccines. These results have important implications for the continuing development of an effective, safe low dose pDNA vaccine adjuvant suitable for human use.

Curcumin inhibits immunostimulatory function of dendritic cells: MAPKs and translocation of NF-kappa B as potential targets

Curcumin has been shown to exhibit anti-inflammatory, antimutagenic, and anticarcinogenic activities. However, the effect of curcumin on the maturation and immunostimulatory function of dendritic cells (DC) largely remains unknown. In this study, we examined whether curcumin can influence surface molecule expression, cytokine production, and their underlying signaling pathways in murine bone marrow-derived DC. DC were derived from murine bone marrow cells and used as immature or LPS-stimulated mature cells. The DC were tested for surface molecule expression, cytokine production, dextran uptake, the capacity to induce T cell differentiation, and their underlying signaling pathways. Curcumin significantly suppressed CD80, CD86, and MHC class II expression, but not MHC class I expression, in the DC. The DC also exhibited impaired IL-12 expression and proinflammatory cytokine production (IL-1beta, IL-6, and TNF-alpha). The curcumin-treated DC were highly efficient at Ag capture, via mannose receptor-mediated endocytosis. Curcumin inhibited LPS-induced MAPK activation and the translocation of NF-kappaB p65. In addition, the curcumin-treated DC showed an impaired induction of Th1 responses and a normal cell-mediated immune response. These novel findings provide new insight into the immunopharmacological role of curcumin in impacting on the DC. These novel findings open perspectives for the understanding of the immunopharmacological role of curcumin and therapeutic adjuvants for DC-related acute and chronic diseases.

Differential expression of dendritic cell markers by all-trans retinoic acid on human acute promyelocytic leukemic cell line

Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs) for naive T cells and play an important role in cancer immunology. All-trans retinoic acid (ATRA) is known to be a differentiating agent in the treatment of acute promyelocytic leukemia (APL). In this study, we investigated whether ATRA can differentiate the retinoic acid (RA)-sensitive promyelocytic leukemic cell line, NB4, to DC-like cells and whether these differentiated cells can activate T cells. NB4 cells were differentiated to myeloid cells by 4, 6, and 8 days of ATRA treatment. NB4 cells up-regulated markers found in DCs, including HLA-DR, costimulatory molecules (CD80 and CD86), adhesion molecules (CD40), and chemokine receptors (CCR6) when cultured for 8 days in the presence of 1 microM ATRA. Upregulation of CD83 was also detected on the surface of ATRA-treated NB4 cells versus untreated cells. The addition of cytokines alone, such as GM-CSF or CD40 ligand, did not affect the expression of CD83 in untreated NB4 cells but they up-regulated CD83 in ATRA-treated cells. CD11b was coexpressed with CD80, CD83, and CD86 in ATRA-treated NB4 cells. In a functional assay, ATRA-treated NB4 cells stimulated T cell proliferation when challenged with Staphylococcus enterotoxin B. These results suggest that the differentiation of NB4 cells by ATRA causes the cells to express DC markers, and that ATRA-differentiated NB4 cells are able to present antigens to T cells.

Lack of an Association between Interleukin-12 Receptor β1 Polymorphisms and Tuberculosis in Koreans

BACKGROUND

The fact that only 10% of people infected with Mycobacterium tuberculosis develop clinical tuberculosis (TB) suggests the presence of genetic factors in the pathogenesis of TB. To date, a number of single nucleotide polymorphisms (SNPs) in several candidate genes have been proposed as genetic risk factors of TB; however, reports are conflicting.

OBJECTIVES

We investigated whether SNPs in the interleukin (IL)-12 receptor beta1 gene are associated with TB in Koreans.

METHODS

One hundred and fifteen patients with bacteriologically or pathologically confirmed TB and 151 healthy anonymous blood donors were enrolled. The genotypes of 5 SNPs on IL-12 receptor beta1 gene, +705A/G (Q214R), +1158T/C (M365T), +1196G/C (G378R), +1637G/A (A525T) and +1664 C/T (P534S), were determined by PCR-RFLP.

RESULTS

No difference was observed between TB patients and controls in terms of the genotype frequencies of the 5 SNPs of the IL-12 receptor beta1 gene or of their haplotypes.

CONCLUSIONS

In view of the finding that these SNPs have been reported to be associated with TB in the Japanese and Moroccan populations, our results may reflect racial differences in genetic susceptibility to TB.

Outer membrane protein P6 of nontypeable Haemophilus influenzae is a potent and selective inducer of human macrophage proinflammatory cytokines

Interactions of nontypeable Haemophilus influenzae (NTHI) with human macrophages contribute to the pathogenesis of NTHI-induced infection in humans. However, the immunologic mechanisms that initiate and perpetuate NTHI-mediated macrophage responses have not been well explored. Outer membrane protein (OMP) P6 is a conserved lipoprotein expressed by NTHI in vivo that possesses a Pam(3)Cys terminal motif, characteristic of immunoactive bacterial lipoproteins associated with Toll-like receptor signaling. We theorized that OMP P6 is a potent immunomodulator of human macrophages. To test this hypothesis, we purified OMP P6 as well as OMP P2, the predominant NTHI outer membrane protein, and lipooligosaccharide (LOS), the specific endotoxin of NTHI, from NTHI strain 1479. Human blood monocyte-derived macrophages, purified from healthy donors, were incubated with each outer membrane constituent, and cytokine production of macrophage supernatants interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNF-alpha), IL-10, IL-12, and IL-8 was measured. OMP P6 selectively upregulated IL-10, TNF-alpha, and IL-8. While OMP P6 (0.1 mug/ml for 8 h) elicited slightly greater concentrations of IL-10, it resulted in over ninefold greater concentrations of TNF-alpha and over fourfold greater concentrations of IL-8 than did OMP P2. OMP P6 at doses as low as 10 pg/ml was still effective at induction of macrophage IL-8, while OMP P2 and LOS were not. OMP P6 of NTHI is a specific trigger of bacteria-induced human macrophage inflammatory events, with IL-8 and TNF-alpha as key effectors of P6-induced macrophage responses.

Effect of water-soluble proteoglycan isolated from Agaricus blazei on the maturation of murine bone marrow-derived dendritic cells

Water-soluble proteoglycan (WSPG) of Agaricus blazei Murill has been known to stimulate the non-specific complements and humoral immune functions to act as polyclonal activators of B cells and to inhibit tumor growth and metastasis. However, little is known about its immunomodulating effects on murine bone marrow (BM)-derived dendritic cells (DC). In the present study, we examined the maturation process of murine BM-DC. BM cells were cultured in the presence of IL-4 and GM-CSF and the generated immature DC were stimulated with WSPG or LPS (WSPG-DC and LPS-DC, respectively) for 24 h. WSPG significantly enhanced the expression of co-stimulatory molecules (CD80 and CD86) and major histocompatibility complex (MHC) II, as did LPS. IL-12p70 production in WSPG-DC was also identical to that in LPS-DC. The antigen-uptake capacity of WSPG-DC was determined by FITC-labeled dextran uptake. WSPG-DC lost dextran uptake capacity comparable to LPS-DC. The antigen-presenting capacity of WSPG-DC as analyzed by allogeneic T cell proliferation was significantly increased in comparison with immature DC, was identical to LPS-DC, and induced higher levels of IL-2 in responding T cells. These results indicate the immunomodulatory properties of WSPG, which might be therapeutically useful in the control of cancers and immunodeficient diseases through the up-regulation of DC maturation.

Mls presentation by peritoneal cavity B cells

DBA/2J spleen and peritoneal cells were compared for their ability to present the minor lymphocyte stimulatory superantigen Mls-1a. Although capable of Mls presentation in vivo, peritoneal cells were less effective than spleen cells in vitro. This difference was not due to cell concentration or culture duration. Flow cytometric comparison of spleen and peritoneal B cells revealed no significant differences in cell surface markers needed for cognate interaction with T cells. Resolution of peritoneal B cell subsets by cell sorting revealed that even though B-1 cells were capable of Mls presentation, they were less effective than B-2 cells. Mixing experiments showed that B-1 cells did not inhibit B-2 cell presentation of Mls. In contrast, total peritoneal cells inhibited T cell responses to Mls presented by spleen cells. The peritoneal cavity harbors B cells that can present Mls as well as other cells that can suppress this response.

Protein microarray analysis of disease activity in pediatric inflammatory bowel disease demonstrates elevated serum PLGF, IL-7, TGF-beta1, and IL-12p40 levels in Crohn's disease and ulcerative colitis patients in remission versus active disease

OBJECTIVES

Cytokines and growth factors play a major role in the dysregulated immune response in inflammatory bowel disease (IBD). We hypothesized that significant differences exist between the serum cytokine and growth factor profiles of pediatric IBD patients with active disease (AD) and those in remission, and that levels of some of these soluble mediators may be used to define regulators in IBD and determine disease activity.

METHODS

Eighty-eight consecutive patients with confirmed Crohn's disease (CD) and ulcerative colitis (UC) seen at the Duke Children's Hospital were prospectively enrolled and a serum sample was obtained. Data were recorded at the time of serum collection to calculate disease activity indices. The relative expression of 78 cytokines, growth factors, and soluble receptors was determined using proprietary antibody-based protein microarrays amplified by rolling circle amplification. SPSS 8 (SPSS Inc., Chicago, IL) was used to compare protein profiles for CD and UC patients in clinical remission (CR) versus AD.

RESULTS

Sixty-five CD patients and 23 UC patients were enrolled. Forty-one CD patients had available samples and PCDAI results. Twenty-two patients were in remission PCDAI < or = 12.5 (median 5), 19 patients had disease activity >15 (median 30). Univariate analysis revealed that PLGF, IL-7, IL-12p40, and TGF-beta1 cytokine levels were significantly elevated for patients in CR versus AD (p < 0.01). Twelve UC serum samples had Seo/Truelove Witt AI for analysis. Five patients were in remission by TW AI and Seo AI < or =110 and 7 patients had active mild-to-severe disease by TW and Seo AI >110. Only one cytokine, IL12p40, showed significance between CR versus AD (p < 0.02).

CONCLUSIONS

Surprisingly, we found no differences in circulating levels of proinflammatory cytokines but found that pediatric IBD patients in remission compared to those with AD had higher levels of specific circulating cytokines, including the regulatory cytokines IL-12p40 and TGF-beta1. It may be that these cytokines directly regulate intestinal inflammation in IBD or reflect the activity of T regulatory cells in negatively regulating the inflammatory response. Further studies will be needed to validate our results to define the molecular pathways involved in the intestinal immune response in man.

Role of cytokines and chemokines in the regulation of innate immunity and HIV infection

The earliest defense against microbial infection is represented by the responses of the innate (or natural) immune system, that also profoundly regulates the adaptive (or acquired) T- and B-cell immune responses. Activation of the innate immune system is primed by microbial invasion in response to conserved structures present in large groups of microorganisms (LPS, peptidoglycan, double-stranded RNA), and is finely tuned by different cell types (including dendritic cells, macrophages, natural killer cells, natural killer T cells, and gammadelta T cells). In addition, several soluble factors (complement components, defensins, mannose-binding lectins, interferons, cytokines and chemokines) can play a major role in the regulation of both the innate and adaptive immunity. In this review, we will briefly overview the regulation of some cellular subsets of the innate immune system particularly involved in human immunodeficiency virus (HIV) infection and then focus our attention on those cytokines and chemokines whose levels of expression are more profoundly affected by HIV infection and that, conversely, can modulate virus infection and replication.

Proteoglycan isolated from Phellinus linteus inhibits tumor growth through mechanisms leading to an activation of CD11c+CD8+ DC and type I helper T cell-dominant immune state

Dendritic cells (DC) are known to not only induce the activation of T cells, but are also associated with the polarization of T cells. This study investigated whether or not proteoglycan (PG) isolated from Phellinus linteus induces the phenotypic and functional maturation of CD11c+ DC in vitro and in vivo. PG was found to induce the phenotypic and functional maturation of bone marrow-derived DC via Toll-like receptors (TLR) 2 and 4 in vitro. Administration of PG in vivo strongly inhibited the MCA-102 tumor growth and increase in vivo. The ratio of CD8+ DC to CD8- DC increased, and PG enhanced IL-12 and IFN-gamma production, and expression of surface molecules including major histocompatibility complexes (MHC) classes I, MHC II, CD80, and CD86 in MCA-102-challenged mice. PG also caused a marked increase in the production of Th (helper T cells)-1 cytokine (IFN-gamma) and a decrease in the production of Th-2 cytokine (IL-4) by splenic cells and inguinal lymph node cells in MCA-102 tumor-bearing mice. Furthermore, PG stimulated the proliferation of CD4+ and CD8+ T cells. In addition, a combination of PG and tumor lysate-pulsed DC inhibited completely the growth of MCA-102 cells in tumor-bearing mice. These results indicate that the administration of PG inhibited the tumor growth through a mechanism leading to a Th-1 dominant immune state and the activation of CD11cCD8+ DC.

Resveratrol inhibits phenotypic and functional maturation of murine bone marrow-derived dendritic cells

This study investigated the effects of resveratrol, a natural polyphenol found in grapes and grape products such as wine and having a wide range of biological and pharmacological activities effecting on the phenotypic and functional maturation of bone marrow (BM)-derived dendritic cells (DC). Resveratrol inhibited the expression of costimulatory molecules (CD80 and CD86), and major histocompatibility complex (MHC) classes I and II significantly, and had the same effect dose-dependently on DC. Resveratrol also significantly suppressed the ability of BM-DC to produce intracellular IL-12 p40/p70 and secretory IL-12 p70 in response to lipopolysaccharides (LPS) stimulation. Resveratrol-treated DC were highly efficient in antigen capture via mannose receptor-mediated endocytosis. Also, they were poor stimulators of naïve allogeneic T-cell proliferation and induced lower levels of IL-2 in responding T cells. These results indicate the immunosuppressive properties of resveratrol, which may be therapeutically useful in controlling chronic immune and/or inflammatory diseases through the down-regulation of DC differentiation and maturation.

Anti-interleukin-12 antibody for active Crohn's disease

BACKGROUND

Crohn's disease is associated with excess cytokine activity mediated by type 1 helper T (Th1) cells. Interleukin-12 is a key cytokine that initiates Th1-mediated inflammatory responses.

METHODS

This double-blind trial evaluated the safety and efficacy of a human monoclonal antibody against interleukin-12 (anti-interleukin-12) in 79 patients with active Crohn's disease. Patients were randomly assigned to receive seven weekly subcutaneous injections of 1 mg or 3 mg of anti-interleukin-12 per kilogram of body weight or placebo, with either a four-week interval between the first and second injection (Cohort 1) or no interruption between the two injections (Cohort 2). Safety was the primary end point, and the rates of clinical response (defined by a reduction in the score for the Crohn's Disease Activity Index [CDAI] of at least 100 points) and remission (defined by a CDAI score of 150 or less) were secondary end points.

RESULTS

Seven weeks of uninterrupted treatment with 3 mg of anti-interleukin-12 per kilogram resulted in higher response rates than did placebo administration (75 percent vs. 25 percent, P=0.03). At 18 weeks of follow-up, the difference in response rates was no longer significant (69 percent vs. 25 percent, P=0.08). Differences in remission rates between the group given 3 mg of anti-interleukin-12 per kilogram and the placebo group in Cohort 2 were not significant at either the end of treatment or the end of follow-up (38 percent and 0 percent, respectively, at both times; P=0.07). There were no significant differences in response rates among the groups in Cohort 1. The rates of adverse events among patients receiving anti-interleukin-12 were similar to those among patients given placebo, except for a higher rate of local reactions at injection sites in the former group. Decreases in the secretion of interleukin-12, interferon-gamma, and tumor necrosis factor alpha by mononuclear cells of the colonic lamina propria accompanied clinical improvement in patients receiving anti-interleukin-12.

CONCLUSIONS

Treatment with a monoclonal antibody against interleukin-12 may induce clinical responses and remissions in patients with active Crohn's disease. This treatment is associated with decreases in Th1-mediated inflammatory cytokines at the site of disease.

The arthritogenic and immunostimulatory properties of phosphorothioate oligodeoxynucleotides rely on synergy between the activities of the nuclease-resistant backbone and CpG motifs

Experiments with immunostimulatory unmethylated CpG-containing DNA are usually conducted with nuclease-protected phosphorothioate oligodeoxynucleotides (S-ODNs), rather than phosphodiester oligodeoxynucleotides (O-ODNs). We compared the murine immune responses to S-ODNs and O-ODNs that either contained or lacked CpG motifs. Both CpG and non-CpG S-ODNs induced synovitis, as did sequence-matched CpG O-ODN, but not GpC O-ODN. There was a minimum length requirement for arthritogenic S-ODNs since a CpC dinucleotide S-ODN did not induce arthritis. There were both sequence- (CpG > non-CpG) and backbone-dependent (S-ODN > O-ODN) differences in the levels of DNA-induced arthritis upon intra-articular injection with the ODNs. However, CpG O-ODN being an exception, induced more severe arthritis than the GpC S-ODN. The levels of in vitro proliferation and production of IL-6, TNF-alpha, IL-12, and RANTES by splenocytes following exposure to CpG S-ODN were significantly higher than those induced by CpG O-ODN. In addition, both proliferative responses and cytokine production induced by S-ODN-stimulated splenocytes increased significantly when the S-ODN contained a CpG motif. Transcription factor NFkappaB was activated by both CpG S-ODN and CpG O-ODN but interestingly not by GpC S-ODN. This indicates that the NFkappaB signal pathway modulates CpG-mediated immunostimulation, while sequence-independent immune activation by the phosphorothioate backbone is probably signalled via a different pathway.

Administration of a polysaccharide from Grifola frondosa stimulates immune function of normal mice

We have reported that D-Fraction, a polysaccharide extracted from the edible maitake mushroom (Grifola frondosa), activates immunocompetent cells, thereby eliciting antitumor activity. To extend the application of D-Fraction as a nutritional supplement for healthy people as well as treatment for those with cancer, we investigated the effects of D-Fraction on the immune system in normal C3H/HeJ mice. Splenocytes from mice administered D-Fraction intraperitoneally for 17 consecutive days were cultured, and the culture supernatants were analyzed for nitric oxide (NO) and interleukin (IL)-12 production by antigen-presenting cells (APCs), including macrophages and dendritic cells, and also for the T helper (Th)-1 cytokine interferon (IFN)-gamma and the Th-2 cytokines IL-4 and IL-10. The level of IL-10 as well as those of NO and IFN-gamma were increased by D-Fraction as compared with the control, in which the serum immunoglobulin E level was increased. The results suggest that D-Fraction induced a Th-2 dominant response through the activation of macrophages, resulting in the enhancement of humoral immunity rather than cell-mediated immunity. Furthermore, an increase in the percentage ratio of CD69 and CD89 expression on major histocompatibility complex II(+) cells revealed activation of APCs 4 h after D-Fraction administration. These results indicate that D-Fraction enhances both the innate and adaptive arms of the immune response in normal mice. Therefore, its administration may enhance host defense against foreign pathogens and protect healthy individuals from infectious diseases.

Avian interleukin-12beta (p40): cloning and characterization of the cDNA and gene

We isolated the chicken interleukin-12 (ChIL-12) p40 cDNA from a concanavalin A (ConA)-stimulated spleen cDNA library using the PCR with primers based on a partial 3' EST sequence in a chicken EST library. The cDNA encodes a polypeptide of 315 amino acids (aa), with a predicted mature peptide of 300 aa. ChIL-12 p40 has 46% and 41% amino acid identity with human (HuIL-12) and murine IL-12 (MuIL-12) p40, respectively. We also isolated a partial turkey IL-12 (TuIL-12) p40 cDNA sequence with 95% predicted aa identity with ChIL-12 p40. The structures of the ChIL-12 p40 gene and its promoter were determined by direct sequencing of a chicken BAC identified by hybridization with the cDNA. The gene structures of HuIL-12, MuIL-12, and ChIL-12 p40 all differ. The promoter of the ChIL-12 p40 gene shares some (an ETS consensus sequence, a C/EBP binding site, and a TATA box) but not all (an NF-kappaB binding site and a GA12 site are absent) of the transcription factor binding sites identified in the human and murine promoters. IL-12 p40 mRNA expression was identified in a wide variety of tissues and in B, T, and macrophage cell lines by RT-PCR.

Role of Cross-Talk between IFN-α-Induced Monocyte-Derived Dendritic Cells and NK Cells in Priming CD8+ T Cell Responses against Human Tumor Antigens

In the present study we evaluated the role of IFN-alpha in the generation of dendritic cells (IFN-DCs) with priming activity on CD8(+) T lymphocytes directed against human tumor Ags. A 3-day treatment of monocytes, obtained as adherent PBMCs from HLA-A*0201(+) healthy donors, with IFN-alpha and GM-CSF led to the differentiation of DCs displaying a semimature phenotype, but promptly inducing CD8(+) T cell responses after one in vitro sensitization with peptides derived from melanoma (gp100(209-217) and MART-1/Melan-A(27-35)) and adenocarcinoma (CEA(605-613)) Ags. However, these features were lost when IFN-DCs were generated from immunosorted CD14(+) monocytes. The ability of adherent PBMCs to differentiate into IFN-DCs expressing higher levels of costimulatory molecules and exerting efficient T cell priming capacity was associated with the presence of contaminating NK cells, which underwent phenotypic and functional activation upon IFN-alpha treatment. NK cell boost appeared to be mediated by both direct and indirect (i.e., mediated by IFN-DCs) mechanisms. Experiments performed to prove the role of contaminating NK cells in DC differentiation showed that IFN-DCs generated in the absence of NK were phenotypically less mature and could not efficiently prime antitumor CD8(+) lymphocytes. Reciprocally, IFN-DCs raised from immunosorted CD14(+) monocytes regained their T cell priming activity when NK cells were added to the culture before IFN-alpha and GM-CSF treatment. Together, our data suggest that the ability of IFN-DCs to efficiently prime anti-tumor CD8(+) T lymphocytes relied mostly on the positive cross-talk occurring between DCs and NK cells upon stimulation with IFN-alpha.

Increased release of IL-12p70 by monocytes after periodontal therapy

OBJECTIVES

It has been suggested that periodontal inflammation may result in an altered immune response. The peripheral immune capacity in periodontitis patients can be investigated using lipopolysaccharide (LPS)-stimulated whole blood cell cultures (WBCC), known to reflect the behavior of monocytes in particular. A previous study in our laboratory revealed that monocytes in the stimulated cultures from periodontitis patients behaved functionally different compared with controls. The present study investigated whether this different response of periodontitis patients' monocytes is intrinsic or acquired.

MATERIAL AND METHODS

The release of inflammatory mediators was measured in Escherichia coli LPS-stimulated WBCC from 12 periodontitis patients before and after periodontal therapy. In addition, the total leukocyte and leukocyte differentiation counts were also determined in the patients before and after therapy.

RESULTS

The levels of interleukin (IL)-12p70 in cell culture supernatants increased two times and those of prostaglandin E2 showed a trend towards reduction after therapy, whereas the levels of IL-1beta, IL-6, IL-8, IL-10, IL-12p40 and tumor necrosis factor-alpha did not change. The total number of white blood cells was decreased after periodontal therapy.

CONCLUSIONS

After periodontal therapy, the functional phenotype of the peripheral blood monocytes from patients was reconstituted, resembling that of subjects without periodontitis.

Interleukin-10 secretion differentiates dendritic cells from human liver and skin

Liver dendritic cells (DCs), which may orchestrate the liver's unique immunoregulatory functions, remain poorly characterized. We used a technique of overnight migration from pieces of normal human liver and skin to obtain tissue-derived DCs with minimal culture and no additional cytokine treatment. Liver and skin DCs had a monocyte-like morphology and a partially mature phenotype, expressing myeloid markers, MHCII, and co-stimulatory molecules; but only the skin DCs contained a population of CD1a+ cells. Overnight-migrated liver DCs activated naïve cord blood T cells efficiently. Liver DCs produced interleukin (IL)-10 whereas skin DCs failed to secrete IL-10 even after stimulation and neither skin nor liver-derived DCs secreted significant amounts of IL-12p70. Compared with skin DCs, liver DCs were less effective at stimulating T-cell proliferation and stimulated T cells to produce IL-10 and IL-4 whereas skin DCs were more potent stimulators of interferon-gamma and IL-4. Monocyte-derived DCs were down-regulated after culture with liver-conditioned media, suggesting that local microenvironmental factors may be important. Thus we show for the first time clear tissue-specific differences in nonlymphoid DCs. Although it is not possible to conclude from our data whether liver DCs are more regulatory, or skin DCs more proimmunogenic, the ability of liver DCs to secrete IL-10 may be important for regulating local immune responses within the liver in the face of constant exposure to gut antigens.

Acidic polysaccharides isolated from Phellinus linteus induce phenotypic and functional maturation of murine dendritic cells

Acidic polysaccharides (PL) isolated from Phellinus linteus are known to stimulate the proliferation of T lymphocytes and humoral immune functions to act as a polyclonal activator of B cells, and to inhibit tumor growth and metastasis. However, little is known about their immunomodulating effects or the effects of its mechanisms on murine bone marrow (BM)-derived dendritic cells (DC). In this study, it profoundly increased CD80, CD86, MHC I, and MHC II expression in murine, GM-CSF and IL-4 stimulated, BM-derived myeloid DC. The ability of unstimulated DC to uptake dextran was higher than that of PL- or LPS-stimulated DC. We analyzed the concentration of IL-12 secreted by DC using flow cytometry and ELISA. Untreated DC secreted a low concentration of IL-12, while PL- or LPS-stimulated DC secreted higher levels of IL-12 than untreated DC. There were no remarkable differences in the concentrations of IL-12 produced by PL- or LPS-stimulated DC. However, polymyxin B (PB; an LPS inhibitor) effectively inhibited the surface molecules and IL-12 production induced by LPS, but had no effect on the PL in DC. PL-treated DC were much more potent antigen-presenting cells in allogeneic immune response than untreated DC. PL treatment not only formed morphologically mature DC but also induced predominant migration to lymphoid tissues. Moreover, the inhibitors of protein tyrosine kinase (PTK) or protein kinase C (PKC) significantly blocked the expression of surface molecules and IL-12 production in PL-stimulated DC. Treatment of DC with PL directly induced PKC activity and phosphorylated PTK. Furthermore, CD11b and/or CD18 partially mediated PL-induced DC maturation.

IL-12 Inhibits Thymic Involution by Enhancing IL-7- and IL-2-Induced Thymocyte Proliferation

IL-12 has been reported to affect thymic T cell selection, but the role of IL-12 in thymic involution has not been studied. We found that in vivo, IL-12b knockout (IL-12b(-/-)) mice exhibited accelerated thymic involution compared with wild-type (WT) B6 mice. This is characterized by an increase in thymocytes with the early development stage phenotype of CD25(-)CD44(+)CD4(-)CD8(-) in aged IL-12b(-/-) mice. Histologically, there were accelerated degeneration of thymic extracellular matrix and blood vessels, a significantly decreased thymic cortex/medulla ratio, and increased apoptotic cells in aged IL-12b(-/-) mice compared with WT mice. There was, however, no apparent defect in thymic structure and thymocyte development in young IL-12(-/-) mice. These results suggest the importance of IL-12 in maintaining thymic integrity and function during the aging process. Surprisingly, in WT B6 mice, there was no age-related decrease in the levels of IL-12 produced from thymic dendritic cells. Stimulation of thymocytes with IL-12 alone also did not enhance the thymocyte proliferative response in vitro. IL-12, however, provided a strong synergistic effect to augment the IL-7 or IL-2 induced thymocyte proliferative response, especially in aged WT and IL-12b(-/-) mice. Our data strongly support the role of IL-12 as an enhancement cytokine, which acts through its interactions with other cytokines to maintain thymic T cell function and development during aging.

Differential expression and regulation of IL-23 and IL-12 subunits and receptors in adult mouse microglia

IL-23 and IL-12 are functionally related heterodimeric cytokines that share the IL-12p40 subunit. IL-23 and IL-12 function through heterodimeric receptors, which share the IL-12Rbeta1 subunit. Production of IL-23, a heterodimer of IL-12p40 and IL-23p19, by CNS antigen-presenting cells (APC) is critical for susceptibility to experimental autoimmune encephalomyelitis (EAE), the animal model for multiple sclerosis (MS). We report that the expression of IL-23p19 mRNA is highly induced by stimulation with IFN-gamma and LPS in adult mouse microglia and a microglia cell line, EOC13. Expression of the IL-12R subunits, IL-12Rbeta1 and IL-12Rbeta2, is upregulated in both microglia and splenic macrophages upon stimulation with LPS or IFN-gamma and LPS, whereas the IL-23R subunit is upregulated only in macrophages. In EAE, an early peak of IL-23p19 mRNA expression is found in CD11b(+) CNS APC, compared with peripheral macrophages. In contrast, IL-12p40 and IL-12p35 mRNA maximum levels in the CNS are detected at peak of disease. The expression of IL-12p35 mRNA is more sustained than that of IL-12p40 and IL-23p19. Thus, IL-23 produced by CNS microglia/macrophages may contribute to the early induction of EAE. In the CNS, IL-23 may preferentially target infiltrating mononuclear cells, which upregulate IL-23R, rather than parenchymal microglia.

Ligation of CD47 During Monocyte Differentiation into Dendritic Cells Results in Reduced Capacity for Interleukin-12 Production

We have previously shown that the CD47-binding thrombospondin-1 (TSP-1)-derived peptide 4N1K induces a rapid apoptosis-like death of human monocytes and dendritic cells (DCs). However, not all cells were susceptible to the peptide-induced cell death and here, we have investigated whether surviving monocytes could differentiate into functionally normal DCs. We found that the cell-surface phenotype, the T-cell stimulatory capacity and the ability to undergo lipopolysaccharide (LPS)-induced maturation into CD83+ DCs were essentially identical in 4N1K-derived and control DCs. Interleukin-10 (IL-10) production was also normal, but a significant downregulation of the pro-inflammatory cytokines IL-12 and tumour necrosis factor-alpha (TNF-alpha) was observed in the 4N1K-derived DCs. To the contrary, simultaneous stimulation of control DCs with 4N1K and LPS + interferon-gamma did not alter IL-12 production. These results indicate that although activation of the TSP-1-binding region of CD47 on monocytes induces apoptosis in a large proportion of the cells, it does not hamper the overall capacity of the surviving cells to differentiate into DCs. Such DCs, however, have a reduced capacity for IL-12 and TNF-alpha production, and the possibility that this is linked to the uptake of apoptotic cells is discussed.

Evidence for increased expression of regulatory cytokine receptors interleukin-12R and interleukin-18R in common variable immunodeficiency

We investigated the expression of T helper (Th)1/Th2 regulatory cytokine receptors on lymphocytes from patients with common variable immunodeficiency (CVID), a disorder associated with raised Th1 cytokine production, comparing the results with those from healthy individuals and atopic asthmatics, the latter generally considered to have a Th2-driven disease. We proposed that alterations in some of the relevant receptors might be related to the observed imbalances in Th1/Th2 cytokines. Cells from CVID patients showed an increase in the percentages of CD212 [interleukin (IL)-12Rbeta1] cells within the CD4+ CD45RA+ and CD8+ CD45RA+ subsets (24% and 41%, respectively), as compared to CD4+ CD45RA+ and CD8+ CD45RA+ in healthy subjects (6% and 23%, respectivey). Approximately 21% of the CD4+ CD45RA+ naïve cells expressed IL-18Ralpha, compared with 11% in healthy subjects. In contrast, the cytokine-receptor expression in asthmatics was similar to that of controls. In spite of the above differences, after 72 h of stimulation with anti-CD3 and anti-CD28, cytokine receptor up-regulation was similar in all three groups, with up to 80% of both CD45RA+ and CD45RO+ lymphocytes expressing CD212 (IL-12Rbeta1) and IL-18Ralpha. Approximately 50% of the 'naïve', and 25% of the 'memory' subpopulations up-regulated IL-12Rbeta2. These findings provide further evidence of a polarization towards a Th1 immune response in CVID, the mechanism possibly involving up-regulation of IL-12-mediated pathways.

Nramp1-mediated innate resistance to intraphagosomal pathogens is regulated by IRF-8, PU.1, and Miz-1

Natural resistance-associated macrophage protein 1 (Nramp1) is a proton/divalent cation antiporter exclusively expressed in monocyte/macrophage cells with a unique role in innate resistance to intraphagosomal pathogens. In humans, it is linked to several infectious diseases, including leprosy, pulmonary tuberculosis, visceral leishmaniasis, meningococcal meningitis, and human immunodeficiency virus as well as to autoimmune diseases such as rheumatoid arthritis and Crohn's disease. Here we demonstrate that the restricted expression of Nramp1 is mediated by the macrophage-specific transcription factor IRF-8. This factor exerts its activity via protein-protein interaction, which facilitates its binding to target DNA. Using yeast two-hybrid screen we identified Myc Interacting Zinc finger protein 1 (Miz-1) as new interacting partner. This interaction is restricted to immune cells and takes place on the promoter Nramp1 in association with PU.1, a transcription factor essential for myelopoiesis. Consistent with these data, IRF-8 knockout mice are sensitive to a repertoire of intracellular pathogens. Accordingly, IRF-8-/- mice express low levels of Nramp1 that can not be induced any further. Thus, our results explain in molecular terms the role of IRF-8 in conferring innate resistance to intracellular pathogens and point to its possible involvement in autoimmune diseases.

Selective suppression of IL-12 production by human herpesvirus 6

Human herpesvirus 6 (HHV-6) is a potentially immunosuppressive agent that has been suggested to act as a cofactor in the progression of HIV disease. Exposure of human macrophages to HHV-6A or HHV-6B profoundly impaired their ability to produce interleukin 12 (IL-12) upon stimulation with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS). By contrast, the production of tumor necrosis factor-alpha (TNF-alpha); regulated on activation, normal T-cell expressed and secreted (RANTES); and macrophage inflammatory protein 1 beta (MIP-1 beta) was not negatively affected. To exclude the involvement of IL-12-suppressive cytokines, such as IL-10 and TNF-alpha, the viral stocks were fractionated by ultra-centrifugation. The bulk of the suppressive activity was recovered within the virion-rich pelleted fraction that was virtually devoid of such cytokines. IL-12 suppression was independent of viral replication, and the effect was not abrogated upon ultraviolet-light inactivation of the viral inoculum. The mechanism of HHV-6-mediated IL-12 suppression was investigated by RNase protection assays, which demonstrated unaltered levels of IL-12 p35 mRNA and only a modest reduction in p40 mRNA, which was insufficient to account for the near-complete loss of both extracellular and intracellular IL-12 protein. Moreover, both the IFN-gamma and the LPS signaling pathways were intact in HHV-6-treated cells. These data suggest that HHV-6 can dramatically affect the generation of effective cellular immune responses, providing a novel potential mechanism of HHV-6-mediated immunosuppression.

Inhibition of interleukin-12 expression by alpha-thrombin in human peripheral blood mononuclear cells: a potential mechanism for modulating Th1/Th2 responses

In addition to its central role in blood coagulation and hemostasis, human alpha-thrombin is a powerful regulator of inflammatory responses and is known to affect cell-mediated immunity. Interleukin (IL)-12 is a strong promoter of the development of Th1-type lymphocytes and its downregulation implies a positive feedback mechanism for development of Th2 responses. We have previously shown that thrombin enhances the release of IL-6, a Th2-related cytokine, in human peripheral blood mononuclear cells (PBMC). Here we show that thrombin downregulates IL-12 production at both protein and mRNA levels in human PBMC. The inhibition of IL-12 production was accompanied by an enhanced release of IL-10, which inhibits Th1-related processes and promotes Th2-type responses. The use of proteolytically inactive thrombin and of the specific thrombin receptor agonist peptide, SFLLRN, reveals that this downregulation is thrombin-specific and requires thrombin proteolytic activity. In addition, activation of coagulation inhibits IL-12 production in whole blood cultures, confirming the tight relationship between the coagulation pathway, where thrombin is a key enzyme, and inflammation. Decreased IL-12 production appears to be related also to IL-10 production, since the addition of an anti-IL-10 monoclonal antibody to thrombin-treated PBMC resulted in a partial restoration of IL-12 production. In conclusion, the observation that thrombin significantly affects the production of IL-12, as well as of IL-10, implies a concerted role orchestrated by thrombin in PBMC that could be crucial to effective immunity and inflammation.

Differences in cytokine synthesis by the sub-populations of dendritic cells from afferent lymph

Two phenotypically distinct subpopulations of dendritic cells (SIRPalpha+ CC81Ag- DC and SIRPalpha- CC81Ag+ DC) have previously been identified in bovine afferent lymph which show functional differences when assayed in vitro. The purpose of this study was to investigate whether differences in cytokine production between the two subpopulations might occur which could influence the bias of the immune response they stimulate. Qualitative and quantitative polymerase chain reactions were used to detect specific mRNA transcripts and flow cytometry and enzyme-linked immunosorbent assays were used to detect protein production. The SIRPalpha- CC81Ag+ DC produced considerably more interleukin-12 (IL-12) mRNA transcripts and protein than the SIRPalpha+ CC81Ag- DC. Conversely, SIRPalpha+ CC81Ag- DC contained more of both transcripts and protein for IL-1 and of transcripts for IL-6. A small percentage of both subpopulations produced interferon-gamma (IFN-gamma) as evidenced by cytoplasmic staining. Stimulation of DC by culture with CD40L+ cells increased the production of IL-1, IL-6 and IL-12 but quantitative differences between the subpopulations remained. Production of IL-10 was also evident following culture with CD40L+ cells or lipopolysaccharide primarily by the SIRPalpha+ CC81Ag- DC. No evidence was found for type 1 IFN production, and hence plasmacytoid DC, by DC in afferent lymph; both subpopulations appear to be myeloid in origin. These different cytokine repertoires of the two subpopulations of ex vivo DC isolated from afferent lymph imply functional differences that could influence the presentation of antigen to T cells and bias of the immune response following vaccination or infection.

Dissociating the enhancing and inhibitory effects of pertussis toxin on autoimmune disease

Pertussis toxin (PT) has both enhancing and inhibitory effects on experimental autoimmune disease, depending on its time of administration relative to immunization. The inhibitory effect is due to blocking of G(i)-coupled receptors by the enzymatic A subunit. In this study, we attribute the enhancing effect of PT to the cell-binding B subunit (PT-B). C57BL/6 mice, a strain that requires PT to develop experimental uveitis, were immunized with a retinal Ag and were injected with whole PT, PT-B, or vehicle. Disease and associated immunological responses were evaluated. The results showed that PT-B, determined to be free of biologically significant contamination with whole PT or with endotoxin, was able to mimic all the effects of PT with respect to disease induction, enhancement of delayed-type hypersensitivity, enhancement of lymphocyte proliferation, induction of an innate IL-12 response, and promotion of an adaptive IFN-gamma response to the uveitogenic Ag. Our results suggest that PT-B is largely responsible for the disease-enhancing properties of PT.

Update on pathways regulating the activation of uterine Natural Killer cells, their interactions with decidual spiral arteries and homing of their precursors to the uterus

Virgin adult C57Bl/6J mouse uterus contains a population of small, non-granulated Natural Killer (NK) cells with balanced expression of NK cell activating and inhibiting LY49 receptors. Coincident with blastocyst implantation and decidualization, uterine (u)NK cells become activated. The surface glycoslyation of uNK changes, the cells proliferate and they induce production of interferon (IFN)gamma, perforin, serine esterases and other molecules, including angiogenic factors. Mouse strains genetically ablated in uNK cells fail to undergo modification of spiral artery segments that branch from the uterine artery and feed into the placenta and these mice do not sustain a robust decidualization response. IFN-gamma is thought, from bone marrow transplantation and therapeutic studies, to be the key uNK-cell derived mediator regulating gene expression in vascular and decidual tissues. Here, we review recent studies showing that IL-15 is the critical cytokine controlling uNK cell differentiation and that uNK cells are activated by either IL-12 or IL-18 and by other factors when both IL-12 and IL-18 are genetically absent from implantation sites. We address possible roles of the IFN-gamma regulated gene alpha2-macroglobulin (alpha2-M) in regulation of the position of fetal trophoblast within the walls of the spiral arteries, and we discuss approaches that have been successful in evaluating mechanisms involved in homing of mouse uNK cell precursors to the uterus. These approaches maybe applicable to studies in women. Our studies show that complex immuno-physiological events contribute to spiral artery modification by mid-gestation in mice.

Against the self: dendritic cells versus cancer

The role of host defense in cancer is highly variable. Although there are cases where spontaneous cures of cancer appear to be mediated by immunologic mechanisms, malignant disease generally progresses even in patients where tumor-specific immunity can be demonstrated. It is apparent that there are complex interactions between tumor cells and dendritic cells, the dominant antigen-presenting cells of the immune system. Through their inhibitory actions upon dendritic cells, tumor cells can negatively regulate priming of tumor-specific immunity. Recent work has also shown that dendritic cells have direct cytotoxic effects upon tumor cells. These interactions may impact on the efficacy of current strategies using dendritic cell-based vaccines for tumor immunotherapy.

Induction of interleukin-12 production in mouse macrophages by berberine, a benzodioxoloquinolizine alkaloid, deviates CD4+ T cells from a Th2 to a Th1 response

In this study we investigated whether berberine-mediated induction of interleukin-12 (IL-12) production in antigen-presenting cells could regulate a cytokine profile of antigen-primed CD4+ T helper (Th) cells. Pretreatment with berberine induced IL-12 production in both macrophages and dendritic cells, and significantly increased the levels of IL-12 production in lipopolysaccharide-stimulated macrophages and in CD40 ligand-stimulated dendritic cells. Importantly, berberine pretreatment of macrophages increased their ability to induce interferon-gamma (IFN-gamma) and reduced their ability to induce IL-4 in antigen-primed CD4+ T cells. Berberine did not influence the macrophage cell surface expression of the class II major histocompatibility complex molecule, the co-stimulatory molecules CD80 and CD86, and intracellular adhesion molecule-1. Addition of neutralizing anti-IL-12p40 monoclonal antibody to cultures of berberine-pretreated macrophages and CD4+ T cells restored IL-4 production in antigen-primed CD4+ T cells. The in vivo administration of berberine resulted in the enhanced induction of IL-12 production by macrophages when stimulated in vitro with lipopolysaccharide or heat-killed Listeria monocytogenes, leading to the inhibition of the Th type 2 cytokine profile (decreased IL-4 and increased IFN-gamma production) in antigen-primed CD4+ T cells. These findings may point to a possible therapeutic use of berberine or medicinal plants containing berberine in the Th type 2 cell-mediated immune diseases such as allergic diseases.

Improved antitumour immunity in murine neuroblastoma using a combination of IL-2 and IL-12

Neuroblastoma immunotherapy using cytokine-modified tumour cells has been tested in clinical trials. However, because of the complex nature of antitumour immune responses, a number of therapies may be required for complete tumour eradication and generation of systemic immunity. We report here the improved antitumour effect of two cytokines, interleukin-2 (IL-2) and interleukin-12 (IL-12), when coexpressed by neuroblastoma cell lines. Initially, transfection of human and mouse neuroblastoma cell lines resulted in high expression levels of biologically active IL-2 and IL-12 in vitro. These cytokines when expressed by transfected Neuro-2A cells completely abolished their in vivo tumorigenicity in a syngeneic neuroblastoma model. Vaccination of established tumours with IL-12-producing cells exhibited a clear effect with reduced tumour growth in the presence of IL-2. In vivo depletion studies showed that CD4(+) and CD8(+) T cells mediate the response against cytokine-producing cells. These results suggest that IL-2 and IL-12, when cotransfected in tumour cells, are effective against established disease and provide a promising immunotherapeutic approach for the treatment of neuroblastoma.

Stimulation of interleukin-12 production in mouse macrophages via activation of p38 mitogen-activated protein kinase by alpha2-adrenoceptor agonists

Interleukin-12 is a cytokine primarily produced by monocytes and macrophages. It plays an essential role in the development of cell-mediated immunity and stimulates T helper type 1 (Th1) immune responses. This study was designed to determine if alpha(2)-adrenoceptor agonists are involved in the induction of interleukin-12 production by macrophages. alpha(2)-adrenoceptor agonists such as clonidine, guanfacine, and oxymetazoline significantly induced interleukin-12 secretion and interleukin-12 mRNA expression by macrophages in a concentration-dependent manner. Moreover, stimulation of alpha(2)-adrenoceptor by their agonists triggered the activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway. Inhibitors of p38 MAPK prevented the stimulatory effects of alpha(2)-adrenoceptor agonists on IL-12 production. Yohimbine and 2-(2,3-dihydro-2-methoxy-1,4-benzodioxin-2-yl)4,5-dihydro-1H-imidazole (RX821002), alpha(2)-adrenoceptor antagonists, significantly blocked agonist-induced interleukin-12 production and p38 MAPK activation, indicating that the effects of the agonists were mediated through alpha(2)-adrenoceptor. In addition, protein kinase C (PKC) inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) and chelerythrine, significantly inhibited guanfacine-induced interleukin-12 production and p38 MAPK in a concentration-dependent manner. These findings show that alpha(2)-adrenoceptor agonists induce interleukin-12 production in mouse macrophages via a PKC/p38 MAPK signaling pathway and suggest that the effect of alpha(2)-adrenoceptor agonists on interleukin-12 secretion may be a new and novel means of augmenting cell-mediated immune responses.

Relationship between dendritic cells and the D-fraction-induced Th-1 dominant response in BALB/c tumor-bearing mice

Dendritic cells (DCs) are known to not only induce the activation of T cells, but are also associated with the differentiation of T cells. The D-fraction, a beta-glucan extracted from maitake (Grifola frondosa) which expresses anti-tumor effects by establishing a helper (Th)-1 dominance in BALB/c mice, enhanced IL-12p70 production by DCs, when the ratio of CD8alpha(+) DCs to CD8alpha(-) DCs increased. In addition, examination of the tumor rejection effect of D-fraction-stimulated DCs loaded with tumor antigen revealed that tumor growth is inhibited completely by activating CD4(+) T cells and CD8(+) T cells.

Influence of interleukin-12 receptor beta1 polymorphisms on tuberculosis

Host genetic factors may be important determinants of susceptibility to tuberculosis, and several candidate gene polymorphisms have been shown to date. A series of recent reports concerning rare human deficiencies in the type-1 cytokine pathway suggest that more subtle variants of relevant genes may also contribute to susceptibility to tuberculosis at the general population level. To investigate whether polymorphisms in the interleukin-12 receptor (IL-12R) gene predispose individuals to tuberculosis, we studied these genes by single-strand conformational polymorphism analysis and direct sequencing. Although no common polymorphisms could be identified in the IL-12R beta 2 gene ( IL-12RB2), we confirmed four single nucleotide polymorphisms (SNPs; 641A-->G, 684C-->T, 1094T-->C, and 1132G-->C) causing three missense variants (Q214R, M365T, G378R) and one synonymous substitution in the extracellular domain of the IL-12R beta 1 gene ( IL12RB1). All SNPs were in almost perfect linkage disequilibrium (D'=0.98), and two common haplotypes of IL12RB1(allele 1: Q214-M365-G378; allele 2: R214-T365-R378) were revealed. Polymerase chain reaction/restriction fragment length polymorphism and sequence analyses were used to type IL12RB1polymorphisms in 98 patients with tuberculosis and 197 healthy controls in Japanese populations. In our case-control association study of tuberculosis, the R214-T365-R378 allele (allele 2) was over-represented in patients with tuberculosis, and homozygosity for R214-T365-R378 (the 2/2 genotype) was significantly associated with tuberculosis (odds ratio: 2.45; 95% CI: 1.20-4.99; P=0.013). In healthy subjects, homozygotes for R214-T365-R378 had lower levels of IL-12-induced signaling, according to differences in cellular responses to IL-12 between two haplotypes. These data suggest that the R214-T365-R378 allele, i.e., variation in IL12RB1, contribute to tuberculosis susceptibility in the Japanese population. This genetic variation may predispose individuals to tuberculosis infection by diminishing receptor responsiveness to IL-12 and to IL-23, leading to partial dysfunction of interferon-gamma-mediated immunity.

Antigen-based immune modulation: DNA vectors and beyond

The ultimate goal for autoimmune immunotherapy is to achieve a specific downregulation or modification of autoaggressive immune responses while leaving in place the normal repertoire, capable of mediating antimicrobial responses. A multitude of preclinical studies, particularly during the last 15 years, raised hopes that self-antigens could be used to achieve the goal of specific immune modulation. Difficulties associated with the translation of this concept to the clinic revealed inherent limitations of antigen-based immune modulation. To increase the efficiency of antigen-dependent immune modulation, researchers started to investigate novel vectors for antigen delivery. Plasmid vectors, as opposed to protein antigens or peptides, have the ability to trigger prolonged production of limited amounts of antigen in the periphery. However, one complicating factor may be the inherent "danger" signal stimulated by the nature of the unmethylated CpG motifs on bacterial plasmid. Currently, various approaches are being explored to improve the efficacy of response while ameliorating the safety concerns of plasmids as immunotherapeutic tools. This manuscript offers a perspective on such efforts and outlines how the knowledge accumulated in the process will help scientists advance to the next generation of immunotherapeutics.

A polysaccharide, extract from Grifola frondosa, induces Th-1 dominant responses in carcinoma-bearing BALB/c mice

A polysaccharide, designated as the D-fraction, extracted from maitake (Grifola frondosa), was reported to have anti-tumor effects by activating macrophages and T cells in C3H/HeN mice in which a Th-1 dominant response was established. In this study using BALB/c mice in which a Th-2 response is genetically dominant, D-fraction reduced the expression of Th-2 cytokine interleukin (IL)-4 but markedly increased the expression of Th-1 cytokine interferon (IFN)-gamma in CD4(+) T cells and also increased IL-12p70 production as well as IFN-gamma production by antigen-presenting cells (APCs), suggesting that D-fraction promotes the differentiation into Th-1 cells of CD4(+) T cells through enhancement of IL-12p70 production by APCs.

HIV-1 protein Vpr suppresses IL-12 production from human monocytes by enhancing glucocorticoid action: potential implications of Vpr coactivator activity for the innate and cellular immunity deficits observed in HIV-1 infection

The HIV-1 protein Vpr has glucocorticoid receptor coactivator activity, potently increasing the sensitivity of glucocorticoid target tissues to cortisol. Patients with AIDS and normal cortisol secretion have manifestations compatible with glucocorticoid hypersensitivity of the immune system, such as suppression of innate and cellular immunities. The latter can be explained by glucocorticoid-induced inhibition of cytokine networks regulating innate and Th1-driven cellular immunity. We demonstrated that extracellularly administered Vpr protein dose-dependently potentiated glucocorticoid-induced suppression of both mRNA expression and secretion of IL-12 subunit p35 and IL-12 holo-protein, but not IL-12 subunit p40 or IL-10, by human monocytes/macrophages stimulated with LPS or heat-killed, formalin-fixed Staphylococcus aureus (Cowan strain 1). This effect was inhibited by the glucocorticoid receptor antagonist RU 486. Also, Vpr changed the expression of an additional five glucocorticoid-responsive genes in the same direction as dexamethasone and was active in potentiating the trans-activation, but not the trans-repression, properties of the glucocorticoid receptor on nuclear factor kappaB- or activating protein 1-regulated simple promoters. Thus, extracellular Vpr enhances the suppressive actions of the ligand-activated glucocorticoid receptor on IL-12 secretion by human monocytes/macrophages. Through this effect, Vpr may contribute to the suppression of innate and cellular immunities of HIV-1-infected individuals and AIDS patients.

Regulation of virus-induced IL-12 and IL-23 expression in human macrophages

IL-23 is a novel cytokine that promotes the proliferation of naive and memory T cells and stimulates their IFN-gamma production. Besides functional similarities, IL-23 bears structural resemblance to IL-12. Biologically active IL-23 is a heterodimer whose p40 subunit is identical to IL-12p40 while its p19 subunit is distantly related to IL-12p35. In the present study we demonstrate that human monocyte-derived macrophages are able to produce IL-23 in response to virus infection. Sendai virus stimulates the expression of p19 and p40 mRNAs in macrophages. Furthermore, it enhances p35 mRNA expression and the production of IL-12. Influenza A virus, in contrast, fails to stimulate IL-12 or IL-23 expression in macrophages. IL-12 and IL-23 contribute to the IFN-gamma-inducing activity that cell culture supernatant from Sendai virus-infected macrophages show in NK-92 cells. The induction of IFN-gamma production occurs in concert with IFN-alphabeta and IL-18, which are also secreted from the virus-infected cells. The IFN-gamma-inducing activity is inhibited by IL-4, which down-regulates the transcription of p19 and p40 genes and the secretion of IFN-alphabeta, IL-12, and IL-18. IFN-gamma, in contrast, up-regulates the p19 and p40 mRNA expression in Sendai virus infection. Thus, IL-4 and IFN-gamma serve as opposing factors in the regulation of IFN-gamma-inducing cytokines, including IL-23, in macrophages.

CD57+ T cells augment IFN-gamma production in a one-way mixed lymphocyte reaction and their expansion after stem cell transplantation in paediatric patients

To clarify the immune response of CD57+ T cells (most of them are CD8+) in peripheral blood (PB) against alloantigens in order to elucidate the T helper 1 (Th 1) immune response, we assessed the role of CD57+ T cells in IFN-gamma (one of the representative Th 1 cytokines) production in a one-way mixed lymphocyte reaction (MLR). In this study, we showed that CD57+ T cells in responder cells were essential for effective IFN-gamma production in allogeneic MLR due partly to the augmentation of the alloresponse of regular T cells. Furthermore, IFN-gamma production in MLR correlated with the proportions of CD57+ T cells in PB regardless of the responders' age. We also showed that the extent of the expansion of CD57+ T cells in paediatric patients after haematopoietic stem cell transplantation (HSCT) was markedly lower than that in adult patients. In addition, CD57+ T cells purified and activated with a combination of cytokines showed a greater cytotoxicity than regular T cells against human umbilical vein endothelial cells. Because IFN-gamma production in one-way MLR is a useful predictor of graft-versus-host disease (GVHD), especially in the acute phase that occurs after allogeneic HSCT, our findings suggested that CD57+ T cells play a role in the development of GVHD and thus may explain the reason as to why a higher donor age is associated with an increased risk of developing GVHD while, in addition, the incidence of severe GVHD in paediatric patients is lower than that in adult patients.

Interleukin-13 receptor in psoriatic keratinocytes: overexpression of the mRNA and underexpression of the protein

Although several cytokines and their receptors have been involved in the development of psoriasis, the etiology is still unknown. In this study we looked for genes possibly involved in the disease by the reverse transcription-polymerase chain reaction differential display technique in lesional and nonlesional skin biopsies from psoriatic patients. We found the mRNA of the alpha1 chain of the interleukin-13 receptor expressed differentially in psoriatic biopsies. By reverse transcription-polymerase chain reaction, we confirmed an overexpression of the alpha1 chain of the IL-13 receptor and alpha chain of the interleukin-4 receptor mRNA in lesional skin psoriatic biopsies, when compared with skin biopsies from healthy subjects (p<0.01). The nonlesional skin obtained from a region close to a lesional zone in psoriatic patients presented also an overexpression of these mRNA in 50% of the samples. Interleukin-13 and interleukin-4 were not detected either as mRNA or as the proteins in any of the biopsies from psoriatic patients or healthy subjects. A monoclonal antibody to the alpha1 chain of the interleukin-13 receptor detected the receptor in the epidermal keratinocytes of psoriatic patients and of healthy subjects; however, the positive antibody reaction was stronger in skin tissue from healthy subjects than in psoriatic lesional skin tissue (p<0.01), although the mRNA was overexpressed. As interleukin-13 is a pleiotropic immunoregulatory cytokine with a variety of effects on different cell types, including monocytes, B lymphocytes, mast cells, and keratinocytes, we suggest, based on our results, that the interleukin-13 receptor possibly plays an important part in the early inflammatory process of psoriasis; however, its function is lost in the psoriatic keratinocytes.

3-hydroxy-3-methylglutaryl coenzyme A reductase-independent inhibition of CD40 expression by atorvastatin in human endothelial cells

OBJECTIVE

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) exert potent anti-inflammatory effects that are independent of their cholesterol-lowering action. We have investigated the effects of these drugs on cytokine-stimulated CD40 expression in human cultured endothelial cells and monocytes.

METHODS AND RESULTS

Reverse transcription-polymerase chain reaction and Western blot analysis revealed that treatment of either cell type with atorvastatin, cerivastatin, or pravastatin (1 to 10 micromol/L) inhibited interferon-gamma plus tumor necrosis factor-alpha-stimulated CD40 expression by approximately 50%, an effect that was not reversed by the HMG-CoA reductase product mevalonic acid (400 micromol/L). In contrast, mevalonic acid prevented the inhibitory effect of atorvastatin on cytokine-stimulated vascular cell adhesion molecule-1 expression and subsequent adhesion of THP-1 monocytes to the cultured endothelial cells. Transcription factor analysis revealed an inhibition by atorvastatin of nuclear factor-kappaB plus signal transducer and activator of transcription-1-dependent de novo synthesis of interferon regulatory factor-1, governing cytokine-stimulated CD40 expression in these cells. One consequence of this statin-dependent downregulation of CD40 expression was a decrease in CD40 ligand-induced endothelial interleukin-12 expression.

CONCLUSIONS

By interfering with cytokine-stimulated CD40 expression in vascular cells, statins thus seem capable of attenuating CD40 ligand-induced proinflammatory responses, including atherosclerosis. In addition, they point to the coexistence of HMG-CoA reductase-dependent and -independent effects of statins in the same cell type.

Peripheral immature CD2-/low T cell development from type 2 to type 1 cytokine production

Immature myeloid and NK cells exist, and undergo cytokine-induced differentiation, in the periphery. In this study, we show that also immature CD2(-/low) T cells exist in peripheral blood. These cells produce the type 2 cytokines IL-13, IL-4, and IL-5, but not IFN-gamma or IL-10, and, upon culture with IL-12- and TCR-mediated stimuli, differentiate to IL-13(+)IFN-gamma(+) cells producing high IL-2 levels, and finally IL-13(-)IFN-gamma(+) cells. The monokine combination IL-12, IL-18, and IFN-alpha substitutes for TCR-mediated stimulation to induce the same differentiation process in both immature CD2(-/low) and primary mature CD2(+) IL-13(+) T cells. IFN-alpha is needed to maintain high level IL-2 production, which is confined to type 2 cytokine-producing cells and lost in the IFN-gamma(+) ones. Upon TCR-mediated stimulation, IFN-gamma(+) cells are then induced to produce IL-10 as they undergo apoptosis. These data indicate that peripheral type 2 cytokine(+) T cells are immature cells that can differentiate to effector IFN-gamma(+) cells following a linear monokine-regulated pathway identical with that previously described for NK cells. They define the cellular bases to support that cell-mediated immune responses are regulated not only via Ag-induced activation of mature effector cells, but also via bystander monokine-induced maturation of immature T cells.

IL-2 receptor blockade inhibits late, but not early, IFN-gamma and CD40 ligand expression in human T cells: disruption of both IL-12-dependent and -independent pathways of IFN-gamma production

mAbs directed against the alpha-chain (Tac/CD25) of the IL-2R are an emerging therapy in both transplantation and autoimmune disease. However, the mechanisms underlying their therapeutic efficacy have not been fully elucidated. Therefore, we examined the effect of IL-2R blockade on Th1 and Th2 cytokine production from human PBMC. Addition of a humanized anti-Tac Ab (HAT) to activated PBMC cultures inhibited IFN-gamma production from CD4 and CD8 T cells by 80-90%. HAT partially inhibited production of TNF-alpha and completely inhibited production of IL-4, IL-5, and IL-10. Furthermore, IL-12, a central regulatory cytokine that induces IFN-gamma, was undetectable in treated cultures. As T cell-dependent induction of IL-12 is regulated via CD40/CD40 ligand (CD40L) interactions, we examined the effect of HAT on CD40L expression. We found CD40L expression to be biphasic with an early (6 h) peak that is CD28/IL-2-independent, but a later peak (48 h) being CD28/IL-2-dependent and inhibited by HAT. Similarly, IFN-gamma production at 6 h was CD28/IL-2-independent but CD28/IL-2-dependent and inhibited by HAT at 48 h. Nonetheless, addition of rCD40L or exogenous IL-12 to HAT-treated cultures could not restore IFN-gamma production. The IFN-gamma deficit in such cultures appears to be due to a direct inhibition by HAT of IL-12-independent IFN-gamma production from T cells rather than altered expression of either the IL-12Rbeta1 or IL-12Rbeta2 chains. These data demonstrate that IL-2 plays a critical role in the regulation of Th1 and Th2 responses and impacts both IL-12-dependent and -independent IFN-gamma production.

IL-12: the role of p40 versus p75

Interleukin (IL)-12p75 is a heterodimeric cytokine composed of the product of two different genes that specify p35 and p40 subunits. The prevailing view is that IL-12 acts as a proinflammatory cytokine that bridges the innate and adaptive immune responses and skews T-cell reactivity toward a TH1 cytokine pattern. Though the terms IL-12 and IL-12p40 are often used interchangeably, and measurements of the p40 chain are often interpreted as measurements of the intact p75 heterodimer, such interchangeable usage may be incorrect. In the following discussion, I will delineate an alternative hypothesis for the roles of the p40 and p75 proteins, suggesting specifically, that: (1) in vivo, secretion of free p40 precedes that of p75 in response to pathogens; (2) induction of p40 is a T-independent response by antigen presenting cells (APCs) to early host-pathogen interactions; and (3) IL-12p75 is a late product, whose induction requires T-dependent signals. It is made as a result, rather than as a cause, of TH1 differentiation. Thus, it is the p40 protein, either alone or paired with other polypeptides, rather than p75, that acts as an interface between the innate and adaptive immune responses.