Cytokine involvement in immunomodulatory activity affected by Candida albicans mannan

Candida albicans mannoprotein (MAN) administered intravenously to mice stimulates the production of splenic CD8+ effector cells which downregulate delayed hypersensitivity (DH) in immunized mice. Cytokine involvement in the induction and/or elicitation of downregulation was studied by (i) examining murine splenocytes qualitatively for mRNA for interleukin-2 (IL-2), IL-4, IL-10, IL-12p40, and gamma interferon (IFN-gamma), (ii) quantitating splenocyte mRNA for IL-12p40 by quantitative-competitive reverse transcriptase-mediated PCR, and (iii) measuring serum levels of IL-12p40 and IL-12p70 by capture enzyme-linked immunosorbent assay, each performed at selected intervals over 96 h after giving MAN. Further, the effect of in vivo administration of anti-IL-4 on the induction and elicitation of MAN-specific DH in MAN-treated mice was measured. Expression of IL-12p40 mRNA in the spleen was reduced to near 0 during the first 24 h but rebounded thereafter. Transcripts for IL-10 were present throughout the 96-h period, whereas those for IL-4 and IFN-gamma were either weak or undetectable prior to 24 to 48 h. In vivo administration of anti-IL-4 partially abrogated the downregulatory effect of MAN only when given at the time of MAN administration. Serum levels of IL-12p40, but not IL-12p70, were increased by 24 h and maximal at 48 h. The antagonistic effect of IL-12p40 could contribute to the mechanism(s) for downregulation of DH. Moreover, IL-10, IL-4, and/or IFN-gamma, interacting with MAN-activated cells in the absence of biologically active IL-12, may induce the production of CD8+ downregulatory effector cells. Partial abrogation of downregulatory activity in animals treated with anti-IL-4 at the time of induction of such activity lends support to this hypothesis.

Substance P diminishes lipopolysaccharide and interferon-gamma-induced TGF-beta 1 production by cultured murine macrophages

Recent evidence has demonstrated the importance of substance P and its receptor in macrophage-mediated inflammatory responses. While previous studies have shown that substance P can augment proinflammatory monokine production, little is known about the effects of this neuropeptide on the production of monokines that might limit inflammation. In the present study we have investigated the effect of substance P treatment on the production of transforming growth factor-beta 1 (TGF-beta 1) in cultured murine macrophages. We report that, while substance P agonist alone elicited increases in TGF-beta 1 mRNA expression and modest increases in TGF-beta 1 secretion, substance P dramatically diminished LPS- or IFN-gamma-induced TGF-beta 1 production. These results suggest a previously unrecognized mechanism where substance P may act as a proinflammatory mediator by limiting the production of excessive levels of TGF-beta 1 by LPS- or IFN-gamma-activated macrophages.

Intracellular Salmonella dublin induces substantial secretion of the 40-kilodalton subunit of interleukin-12 (IL-12) but minimal secretion of IL-12 as a 70-kilodalton protein in murine macrophages

The induction by intracellular pathogens of interleukin-12 (IL-12) secretion is of particular importance since this cytokine has been shown to be necessary for optimal cell-mediated immune responses. Several recent investigations have suggested that cultured macrophages are a significant source of IL-12 following intracellular infection with pathogens such as Salmonella spp. In an effort to critically evaluate the magnitude of the IL-12 response in cultured macrophages following interaction with Salmonella dublin, enzyme-linked immunosorbent assays specific for the 40- and 70-kDa subunits of IL-12 (IL-12p40 and IL-12p70) and a sensitive bioassay for IL-12p70 were used. Using BALB/c macrophages, S. dublin at various challenge doses was a potent inducer of IL-12p40 secretion (>6,000 pg/10(7) macrophages). However when secretion of IL-12p70 was evaluated, S. dublin did not induce comparable IL-12p70 production (<80 pg/10(7) macrophages) at any time, despite varying the challenge dose of Salmonella. The limited ability of BALB/c (Ity(s)) macrophages to secrete IL-12p70 in response to Salmonella was not a strain-specific phenomenon since similar results were demonstrated for macrophages isolated from CBA/J (Ity(r)) and C3H/HeJ (lipopolysaccharide [LPS]-hyporesponsive) mice. While intracellular infection with Salmonella was not a potent stimulus for IL-12p70 secretion in these mouse strains, macrophages from these mice responded significantly to a stimulus of gamma interferon plus LPS. Taken together these results demonstrate a limited capacity for intracellular Salmonella to stimulate murine macrophage secretion of IL-12p70, despite being a significant stimulus for IL-12p40 secretion. Furthermore, our results suggest that Salmonella-induced IL-12p40 secretion by macrophages is not solely an LPS-mediated event.

Reverse transcriptase-polymerase chain reaction amplification and partial sequence of T helper 1- and T helper 2-type lymphokine genes from the owl monkey (Aotus trivirgatus)

The reverse transcriptase-polymerase chain reaction (RT-PCR) was used to amplify selected lymphokine mRNAs from phytohemagglutinin-activated leukocytes of the owl monkey (Aotus trivirgatus). Interleukin-2 (IL-2), IL-4, IL-13, and interferon-gamma were selected as lymphokine mRNAs of interest, since expression of these cytokines helps define the type of T helper lymphocyte response (i.e., TH1 versus TH2). Because sequences for these lymphokine genes were not available for the owl monkey, multiple PCR primers for each lymphokine gene were designed based on published human sequences. Various PCR primer pairs were then used in the RT-PCR to determine the conditions for optimal amplification of each owl monkey cytokine mRNA. In addition, each PCR primer pair was compared for the ability to amplify lymphokine mRNAs from other primate species, including African green (Cercopithecus aethiops), squirrel (Saimiri sciureus), and rhesus (Macaca mulatta) monkeys. The specificity and sensitivity of optimal primer pair was also demonstrated by amplification of as little as 10 fg of each lymphokine gene in a background of 300 ng of irrelevant cDNA. Finally, partial sequences of owl monkey coding regions for IL-2, IL-13, and interferon-gamma were determined and compared for homology with their human counterparts. Together, these studies define specific and sensitive conditions for detection of lymphokine mRNA expression in the owl monkey and provide partial sequence information of the coding region for these lymphokines. This investigation should provide molecular probes to investigate the immune response against malaria and the effectiveness of malaria vaccines in the owl monkey that models this human disease.

Substance P-induced IL-12 production by murine macrophages

Previous investigations in our laboratory have suggested that substance P (NK-1) receptor expression by macrophages contributes to the resistance against the intracellular bacterial pathogen, Salmonella. To investigate possible mechanisms for such resistance, macrophages were cultured with varying concentrations of a substance P agonist to investigate the ability of this neuropeptide to augment IL-12 expression. The substance P agonist was a potent inducer of both IL-12p35 and IL-12p40 mRNA expression in cultured macrophages. The kinetics of this response were maximal within 6 h and could be observed with concentrations of substance P agonist as low as 0.1 nM. The nonpeptide, substance P receptor antagonist, CP96-345, significantly blocked agonist-induced IL-12 mRNA expression, further demonstrating that this effect was mediated through an NK-1 receptor. Substance P agonist alone could stimulate substantial secretion of IL-12p40, but not IL-12p70, by cultured macrophages. Thus, the substance P agonist had the ability to augment IL-12p35 and IL-12p40 mRNA expression, but not to increase IL-12p70 secretion. Like IFN-gamma, we found that substance P could combine with LPS to significantly augment the secretion of bioactive IL-12p70. The costimulatory effects of substance P agonist plus LPS on IL-12 mRNA expression were additive; however, this combination resulted in synergistic secretion of IL-12p70 by macrophages. Together, these results demonstrate the ability of NK-1 receptors to signal IL-12 production by macrophages and suggest mechanisms for substance P-induced modulation of cellular immunity.

Substance P-induced IL-12 production by murine macrophages

Previous investigations in our laboratory have suggested that substance P (NK-1) receptor expression by macrophages contributes to the resistance against the intracellular bacterial pathogen, Salmonella. To investigate possible mechanisms for such resistance, macrophages were cultured with varying concentrations of a substance P agonist to investigate the ability of this neuropeptide to augment IL-12 expression. The substance P agonist was a potent inducer of both IL-12p35 and IL-12p40 mRNA expression in cultured macrophages. The kinetics of this response were maximal within 6 h and could be observed with concentrations of substance P agonist as low as 0.1 nM. The nonpeptide, substance P receptor antagonist, CP96-345, significantly blocked agonist-induced IL-12 mRNA expression, further demonstrating that this effect was mediated through an NK-1 receptor. Substance P agonist alone could stimulate substantial secretion of IL-12p40, but not IL-12p70, by cultured macrophages. Thus, the substance P agonist had the ability to augment IL-12p35 and IL-12p40 mRNA expression, but not to increase IL-12p70 secretion. Like IFN-gamma, we found that substance P could combine with LPS to significantly augment the secretion of bioactive IL-12p70. The costimulatory effects of substance P agonist plus LPS on IL-12 mRNA expression were additive; however, this combination resulted in synergistic secretion of IL-12p70 by macrophages. Together, these results demonstrate the ability of NK-1 receptors to signal IL-12 production by macrophages and suggest mechanisms for substance P-induced modulation of cellular immunity.

Increased susceptibility of mice to Salmonella infection following in vivo treatment with the substance P antagonist, spantide II

Successful resolution of salmonellosis in naive mice depends in large part upon IL-12-induced IFN-gamma production to eliminate this intracellular pathogen of macrophages. In the present study we questioned the contribution that expression of substance P receptors makes to the protective response following oral inoculation with a lethal dose of Salmonella. Such a relationship was suggested when oral inoculation with Salmonella induced rapid and dramatic increases in substance P receptor mRNA expression within Peyer's patches and mesenteric lymph nodes and subsequently in the spleen. The importance of substance P receptor expression in vivo was further suggested by pretreatment of mice with the substance P antagonist, spantide II, before oral inoculation with Salmonella. Mice pretreated with spantide II and then orally inoculated developed advanced salmonellosis and had significantly reduced survival rates compared with mice pretreated with a control peptide. Treatment with spantide II significantly reduced early Salmonella-induced IL-12p4O and IFN-gamma mRNA expression at mucosal sites, suggesting a mechanism for the reduced ability of spantide II-treated mice to resist this pathogen. Increased susceptibility to salmonellosis was not due to 1) spantide II-induced alterations in the uptake of this pathogen from the gut, 2) global spantide II-mediated immune suppression, or 3) nonsubstance P receptor-mediated effects of spantide II on macrophages. The ability of Salmonella to induce substance P receptor expression on cultured macrophages suggested that one mechanism for resistance against this intracellular pathogen might be a direct effect of substance P on this cell population.

Increased susceptibility of mice to Salmonella infection following in vivo treatment with the substance P antagonist, spantide II

Successful resolution of salmonellosis in naive mice depends in large part upon IL-12-induced IFN-gamma production to eliminate this intracellular pathogen of macrophages. In the present study we questioned the contribution that expression of substance P receptors makes to the protective response following oral inoculation with a lethal dose of Salmonella. Such a relationship was suggested when oral inoculation with Salmonella induced rapid and dramatic increases in substance P receptor mRNA expression within Peyer's patches and mesenteric lymph nodes and subsequently in the spleen. The importance of substance P receptor expression in vivo was further suggested by pretreatment of mice with the substance P antagonist, spantide II, before oral inoculation with Salmonella. Mice pretreated with spantide II and then orally inoculated developed advanced salmonellosis and had significantly reduced survival rates compared with mice pretreated with a control peptide. Treatment with spantide II significantly reduced early Salmonella-induced IL-12p4O and IFN-gamma mRNA expression at mucosal sites, suggesting a mechanism for the reduced ability of spantide II-treated mice to resist this pathogen. Increased susceptibility to salmonellosis was not due to 1) spantide II-induced alterations in the uptake of this pathogen from the gut, 2) global spantide II-mediated immune suppression, or 3) nonsubstance P receptor-mediated effects of spantide II on macrophages. The ability of Salmonella to induce substance P receptor expression on cultured macrophages suggested that one mechanism for resistance against this intracellular pathogen might be a direct effect of substance P on this cell population.

Epitope maps of the Escherichia coli heat-labile toxin B subunit for development of a synthetic oral vaccine

Linear B- and T-cell epitopes spanning all 103 amino acids of the Escherichia coli heat-labile toxin B subunit (LT-B) were assessed in mice orally immunized with native LT or with recombinant Salmonella enteritidis expressing LT-B. Oral administration of native LT induced mucosal immunoglobulin A (IgA) antibodies reactive with an epitope at residues 85 to 91, while IgA induced by recombinant Salmonella LT-B reacted with an epitope at residues 36 to 44. Serum IgG anti-LT-B antibodies from mice orally immunized with either LT or with recombinant Salmonella LT-B were directed to both epitopes. A single T-cell epitope spanning residues 34 to 42 was identified by T-cell proliferative and cytokine responses. When a 20-mer peptide (residues 26 to 45) with B- and T-cell epitopes was given orally to BALB/c (H-2(d)) and B10 congenic (I-A(d), I-A(b), and I-A(k)) mice, significant fecal IgA and serum IgG anti-LT-B antibodies were induced. The peptide also induced LT-B-specific T-cell proliferative responses in these mice. Orally administered LT-B peptide (residues 26 to 45) induced a cytokine profile indicative of both T helper 1- and 2-type cells. The remarkable immunogenicity of this 20-mer peptide makes it a candidate for a vaccine to protect against enterotoxigenic E. coli.

Endogenous and exogenous interleukin-12 augment the protective immune response in mice orally challenged with Salmonella dublin

Following oral challenge with Salmonella dublin, we observed significant increases in interleukin-12 (IL-12) protein expression in the mesenteric lymph nodes. The importance of this endogenous cytokine production in the immune response against S. dublin was demonstrated by in vivo depletion of IL-12 with an anti-IL-12 monoclonal antibody prior to oral S. dublin challenge. Mice pretreated with anti-IL-12 antibody had increased salmonellosis and reduced survival times compared with mice receiving control antibody. Furthermore, administration of exogenous murine recombinant IL-12 dramatically increased survival times of mice challenged orally with S. dublin. Together, these results demonstrate that endogenous and exogenous IL-12 significantly augment the mucosal immune response against the intracellular pathogen S. dublin.

In vivo treatment with anti-interleukin-13 antibodies significantly reduces the humoral immune response against an oral immunogen in mice

Interleukin-13 (IL-13) is a cytokine which significantly enhances the proliferation and differentiation of B lymphocytes. We therefore evaluated its role in the formation of a humoral immune response in vivo. Upon oral immunization with the B subunit of Escherichia coli heat-labile enterotoxin (LT-B), rapid up-regulation of IL-13 mRNA expression in the mesenteric lymph nodes of LT-B intubated mice occurred. This result suggested that IL-13 might be involved in the formation of a mucosal antibody response against LT-B if this cytokine was in fact secreted. To test this possibility, the coding region for murine IL-13 was cloned into the pFLAG-1 expression vector. Recombinant murine IL-13 was purified from bacterial lysates and used as an immunogen to produce polyclonal anti-IL-13 antibodies. Groups of BALB/c mice treated in vivo with anti-IL-13 antibody 2 days before and on the day of oral immunization with LT-B had significantly reduced intestinal IgA and serum IgG and IgA anti-LT-B antibody responses when compared to mice treated with control antibody. Furthermore, groups of mice primed with LT-B and then treated with anti-IL-13 antibody prior to oral immunization with a second dose of LT-B also had significantly reduced intestinal IgA and serum IgG and IgA anti-LT-B antibody titres compared to controls. In vitro LT-B restimulation experiments using splenic mononuclear leucocytes isolated from LT-B primed mice treated with anti-IL-13 antibody demonstrated decreased expression of IL-4 and IL-13 mRNA and decreased IL-4 secretion when compared to controls. Together these results demonstrate an important role for IL-13 in the formation of a humoral immune response at mucosal surfaces.

Differential production of interleukin-12 mRNA by murine macrophages in response to viable or killed Salmonella spp

The use of attenuated Salmonella spp. as live oral vaccine carriers fo r foreign antigens has been extensively studied. We have shown that appropriately prepared nonviable organisms are as effective as viable organisms in eliciting humoral immune responses against a foreign antigen delivered by these vectors. It is not clear how strain viability affects the development of a cell-mediated immune response. In the present study, we demonstrate that BALB/c mice orally immunized with viable attenuated Salmonella spp. were protected against subsequent challenge while animals immunized with killed organisms were not. Protection was correlated with increased production of interleukin-12 (IL-12) p40 mRNA in the Peyer's patches within hours of oral administration. Peritoneal macrophages from lipopolysaccharide (LPS)-responsive and LPS-unresponsive mice were also examined for production of IL-12 p40 mRNA following exposure to the viable or killed attenuated Salmonella carrier. There was dramatic upregulation of IL-12 p40 mRNA following exposure of macrophages to either viable or killed organisms. By 4 h postexposure, viable organisms had induced a 27-fold increase in IL-12 p40 mRNA levels while killed organisms had induced a 9-fold increase in IL-12 p40 mRNA levels. This was observed in macrophages isolated from both LPS-responsive and unresponsive mice. The higher levels of IL-12 induced by viable Salmonella spp. may result in the development of a Th1 response and cell mediated immunity, while the lower levels of IL-12 induced by killed Salmonella spp. may not be sufficient to promote a Th1 response.

Mechanisms for mucosal immunogenicity and adjuvancy of Escherichia coli labile enterotoxin

Escherichia coli labile toxin (LT) was assessed as mucosal immunogen and as adjuvant for tetanus toxoid (TT) in mice. After oral administration of LT, C57BL/6 (H-2b) and BALB/c(H-2d) mice were high mucosal and serum antibody responders, while C3H/HeN (H-2k) mice were low responders. High responders exhibited mainly serum IgG (including IgG1, IgG2a, and IgG2b), as well as IgM and IgA, while mucosal responses were IgA. Analysis of LT-B-specific CD4+ T helper (Th) cells from Peyer's patches (PP) or from spleen revealed a mixed Th1 (interferon-gamma) and Th2 (interleukin-4 and -5) cell pattern. Oral LT given with TT induced TT-specific response patterns identical to LT-B. Analysis of mRNA from TT-specific PP CD4+ Th cells also revealed a mixed Th1- and Th2- type response. Thus, antibody response profiles induced by LT are regulated by both CD4+ Th1 and Th2 cell types.

Mechanisms that contribute to the development of lymphoid malignancies: roles for genetic alterations and cytokine production

Recent studies have defined genetic alterations commonly associated with transformed lymphocytes. This review suggests roles for these alterations in the development of lymphoid neoplasms. Damage to the genes encoding proteins that function in intracellular signaling, transcription, or regulation of the cell cycle has been identified and linked at varying degrees to the progression of certain lymphoid malignancies. An understanding of the mechanistic consequences following such genetic alterations is essential to an understanding of the development of these lymphoid neoplasms. In contrast, it is also becoming clear that the dysregulated expression of proteins that are not genetically altered can also contribute to the progression of lymphoid malignancies. One such example is the excessive expression of "normal" lymphokines of cytokines which accompanies many lymphoproliferative diseases. The dysregulated expression of cytokines during malignancy can result in the augmentation of growth of transformed lymphocytes, as well as an alteration of the anti-tumor immune response. The latter mechanism is especially important because evasion of the impending immune response is a prerequisite for the progression of lymphoproliferative diseases. Taken together, this review supports the notion that the development of lymphoid malignancies is multifactorial, involving genetic alterations as well as dysregulated cytokine expression.

Inducible preprotachykinin mRNA expression in mucosal lymphoid organs following oral immunization with Salmonella

Using a sensitive and specific reverse transcribed-polymerase chain reaction (RT-PCR), it was possible to quantify relative increases in preprotachykinin (PPT) mRNA expression in vivo following oral administration of Salmonella. Despite the presence of constitutive levels of PPT mRNA expression in the Peyer's patches, expression of this mRNA increased within 20 h following oral administration of Salmonella. Increases in PPT mRNA expression were also detected in both the mesenteric lymph nodes and spleens following Salmonella administration despite the lack of constitutive PPT mRNA expression in these lymphoid organs. Furthermore, mononuclear leukocytes contributed to this increased expression of PPT mRNA, suggesting that the initial immune response against Salmonella occurs in the presence of increased tachykinin expression.

Thapsigargin and cyclopiazonic acid initiate rapid and dramatic increases of IL-6 mRNA expression and IL-6 secretion in murine peritoneal macrophages

Two different inhibitors of endosomal calcium ATPase activity, cyclopiazonic acid and thapsigargin, were shown to release a common intracellular calcium pool in normal, murine macrophages. Furthermore, the release of this pool was accompanied by increased calcium uptake from the extracellular medium. The activity of these inhibitors was linked to an important biologic response, because both cyclopiazonic acid and thapsigargin induced rapid and dramatic increases in IL-6 mRNA expression and secretion. Compared with control cultures, macrophages treated with these inhibitors increased IL-6 mRNA expression approximately 10-fold by 15 min and approximately 20-fold by 2 h, as determined using quantitative competitive-reverse transcribed-PCRs. The increased mRNA expression was coupled to translation and secretion of this monokine since cyclopiazonic acid and thapsigargin induced significant increases in IL-6 secretion as early as 2 h, and up to approximately 70-fold increases by 20 h, when compared with control cultures. Taken together, these results demonstrate that both cyclopiazonic acid and thapsigargin generate potent intracellular signals that initiate rapid and dramatic production of IL-6. Both thapsigargin and cyclopiazonic acid increased IL-6 mRNA expression at 15 min in the absence of Ca2+ influx from the extracellular medium. These results suggest that events associated with endosomal Ca(2+)-ATPase inhibition contribute to the activation of normal macrophages as defined by increased monokine secretion.

Thapsigargin and cyclopiazonic acid initiate rapid and dramatic increases of IL-6 mRNA expression and IL-6 secretion in murine peritoneal macrophages

Two different inhibitors of endosomal calcium ATPase activity, cyclopiazonic acid and thapsigargin, were shown to release a common intracellular calcium pool in normal, murine macrophages. Furthermore, the release of this pool was accompanied by increased calcium uptake from the extracellular medium. The activity of these inhibitors was linked to an important biologic response, because both cyclopiazonic acid and thapsigargin induced rapid and dramatic increases in IL-6 mRNA expression and secretion. Compared with control cultures, macrophages treated with these inhibitors increased IL-6 mRNA expression approximately 10-fold by 15 min and approximately 20-fold by 2 h, as determined using quantitative competitive-reverse transcribed-PCRs. The increased mRNA expression was coupled to translation and secretion of this monokine since cyclopiazonic acid and thapsigargin induced significant increases in IL-6 secretion as early as 2 h, and up to approximately 70-fold increases by 20 h, when compared with control cultures. Taken together, these results demonstrate that both cyclopiazonic acid and thapsigargin generate potent intracellular signals that initiate rapid and dramatic production of IL-6. Both thapsigargin and cyclopiazonic acid increased IL-6 mRNA expression at 15 min in the absence of Ca2+ influx from the extracellular medium. These results suggest that events associated with endosomal Ca(2+)-ATPase inhibition contribute to the activation of normal macrophages as defined by increased monokine secretion.

Dormant microbes in interstitial cystitis

Interstitial cystitis (IC) is an inflammatory disease of the urinary bladder that has no known etiology. A microbial association with this disease has not been supported since routine cultures of urine from IC patients are usually negative. However, we have demonstrated the presence of bacterial 16S rRNA genes in bladder biopsies from 29% of patients with IC, but not from control patients with other urological diseases. The ability to identify the presence of bacterial DNA in these patients was accomplished using a sensitive and specific nested PCR method capable of amplifying 16S rRNA genes from a wide variety of bacterial genera. Cloning and sequencing of 16S rRNA gene fragments amplified from bladder tissue of IC patients showed that these genes were derived from genera representing Gram-negative bacteria. In addition to the molecular data, a novel finding of 0.22 micron. filterable forms has been isolated in culture from the biopsy tissue of 14 of 14 IC patients and from 1 of 15 controls. The forms contain nucleic acids and resemble cell wall-deficient bacteria in gross morphology; however, their swirled myelin-like ultrastructure is unusual and suggests a heretofore unclassified microbe. These results demonstrate for the first time an association of Gram-negative bacterial DNA and filterable forms with affected bladder tissue from patients with IC.

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.

Lymphokine mRNA expression by transplantable murine B lymphocytic malignancies. Tumor-derived IL-10 as a possible mechanism for modulating the anti-tumor response

In vitro and in vivo expressions of cytokine mRNAs by four transplantable murine B lymphocytic malignancies designated A20, MOPC 315, 2PK-3, and RAW 8.1 were determined using sensitive reverse-transcribed (RT)-PCR. Despite significant differences in both the stage of B cell differentiation represented by each cell line and the method used to induce the original B lymphocytic tumors, IL-6 and IL-10 mRNAs were detected in each of the cultured cell lines. Whereas IL-2, IL-4, IL-5, and IL-12 mRNAs were not detected in cultured cells, expression of cytokine mRNAs in solid tumor tissue was quite different. RT-PCR of poly(A)+ RNA isolated from each of the four solid tumors demonstrated the presence of IL-4, IL-5, IL-6, IL-10, TGF-beta 1, and TNF-alpha mRNAs. There was a noticeable lack of significant IL-2 mRNA expression in any of the solid tumors. Using RT-PCR, it was clear that each of the malignant B lymphocytes expressed IL-6, IL-10, TGF-beta 1, and TNF-alpha, with limited expression of IL-4 and IL-5. To explore the mechanisms that might contribute to the lack of IL-2 mRNA in these solid tumors, quantitative competitive (QC)-RT-PCR was used to quantify expression of IL-10 mRNA. MOPC 315 tumor expressed the most IL-10 mRNA (23.2 pg/micrograms of poly(A)+ RNA), whereas 2PK-3, A20, and RAW 8.1 tumors expressed 7.4, 2.6, and 0.6 pg/micrograms of poly(A)+ RNA, respectively. Secretion of IL-10 into culture supernatants or into sera and ascitic fluid of tumor-bearing animals correlated with mRNA expression. This dysregulated IL-10 production in animals with B lymphocytic tumors suggested a mechanism that may account for the lack of IL-2 mRNA expression in solid tumors, and suggested a possible mechanism by which malignant B lymphocytes may limit cell-mediated antitumor responses.

Lymphokine mRNA expression by transplantable murine B lymphocytic malignancies. Tumor-derived IL-10 as a possible mechanism for modulating the anti-tumor response

In vitro and in vivo expressions of cytokine mRNAs by four transplantable murine B lymphocytic malignancies designated A20, MOPC 315, 2PK-3, and RAW 8.1 were determined using sensitive reverse-transcribed (RT)-PCR. Despite significant differences in both the stage of B cell differentiation represented by each cell line and the method used to induce the original B lymphocytic tumors, IL-6 and IL-10 mRNAs were detected in each of the cultured cell lines. Whereas IL-2, IL-4, IL-5, and IL-12 mRNAs were not detected in cultured cells, expression of cytokine mRNAs in solid tumor tissue was quite different. RT-PCR of poly(A)+ RNA isolated from each of the four solid tumors demonstrated the presence of IL-4, IL-5, IL-6, IL-10, TGF-beta 1, and TNF-alpha mRNAs. There was a noticeable lack of significant IL-2 mRNA expression in any of the solid tumors. Using RT-PCR, it was clear that each of the malignant B lymphocytes expressed IL-6, IL-10, TGF-beta 1, and TNF-alpha, with limited expression of IL-4 and IL-5. To explore the mechanisms that might contribute to the lack of IL-2 mRNA in these solid tumors, quantitative competitive (QC)-RT-PCR was used to quantify expression of IL-10 mRNA. MOPC 315 tumor expressed the most IL-10 mRNA (23.2 pg/micrograms of poly(A)+ RNA), whereas 2PK-3, A20, and RAW 8.1 tumors expressed 7.4, 2.6, and 0.6 pg/micrograms of poly(A)+ RNA, respectively. Secretion of IL-10 into culture supernatants or into sera and ascitic fluid of tumor-bearing animals correlated with mRNA expression. This dysregulated IL-10 production in animals with B lymphocytic tumors suggested a mechanism that may account for the lack of IL-2 mRNA expression in solid tumors, and suggested a possible mechanism by which malignant B lymphocytes may limit cell-mediated antitumor responses.

Role of intracellular Ca2+ stores in the regulation of electrogenic plasma membrane Ca2+ uptake in a B-lymphocytic cell line

Experiments were undertaken to investigate the role of intracellular Ca2+ stores in the regulation of Ca2+ uptake in the cultured B-lymphocytic cell line CH12.LX.C4.5F5. Release of intracellular Ca2+ stores by addition of thapsigargin was accompanied by a biphasic increase in intracellular calcium concentration [Ca2+]i). The initial rise in [Ca2+]i was due to release of Ca2+ from intracellular stores as determined by its maintenance in the absence of extracellular Ca2+. The secondary phase was 1) dependent on the presence of extracellular Ca2+, 2) inhibited by 5 mM extracellular Ni2+, and 3) inhibited by high K+, consistent with electrogenic Ca2+ uptake from the extracellular medium. In order to more accurately investigate the electrogenic nature of this pathway we measured the membrane potential changes accompanying Ca2+ influx stimulated by release of Ca2+ from intracellular stores using bis(1,3-diethylthiobarbituric acid trimethine) oxonol in Bapta-loaded cells. Addition of 5 mM Ca2+ to cells pretreated with doses of thapsigargin or ionomycin shown to release intracellular Ca2+ stores induced a depolarization which was 1) dependent upon extracellular Ca2+, 2) abolished by 5 mM Ni2+, 3) independent of extracellular Na+, and 4) dependent upon Bapta loading. This depolarization was followed by a charybdotoxin-sensitive repolarization consistent with secondary activation of K+ channels. Changes in [Ca2+]i monitored under identical conditions were monitored fluorimetrically using indo-1 and were found to correlate with the changes in Em. On the basis of these data we conclude that an electrogenic Ca(2+)-permeable pathway exists in this B-lymphocytic cell line which is regulated by the degree of filling of an internal Ca(2+)-store.

Control of IL-6 expression and response in fibroblasts from patients with systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune connective tissue disease of unknown etiology in which aberrant fibroblast function results in fibrosis of the skin and internal organs. A distinguishing feature of dermal fibroblasts cultured from SSc lesions is that they produce constitutively, i.e., without exogenous stimulation, as much as 30-fold more interleukin-6 (IL-6) than do normal fibroblasts. The present study indicates that the mechanism of constitutive IL-6 secretion involves the accumulation of IL-6 mRNA in affected SSc fibroblasts, mediated by the constitutive binding of nuclear factors to the IL-6 promoter. DNA-protein complexes formed using nuclear extracts of constitutively expressing cells are distinct from those using extracts of normal cells, with or without exogenous stimulation of IL-6; thus, the mechanisms which regulate constitutive and inducible IL-6 gene expression are apparently distinct. The data also demonstrate that dermal fibroblasts respond very rapidly to IL-6 by increasing expression of the IL-6 gene, thus suggesting a mechanism for the establishment and/or persistence of constitutive expression. The constitutive secretion of IL-6 may play an important role in the perpetuation of the local immune dysregulation and fibroblast activation in the SSc lesion.

Nitric oxide mediates immune dysfunction in the spontaneously hypertensive rat

The immune system of the spontaneously hypertensive rat is dysfunctional compared with that of normotensive control strains. Previous studies from our laboratory have shown that immunodepression in the spontaneously hypertensive rat was mediated by macrophages. The current study examines the mechanism for the depressed proliferative responses to concanavalin A typically observed by splenic mononuclear cells of spontaneously hypertensive rats. We tested various inhibitors of known macrophage products responsible for suppressing lymphoid function. The nitric oxide synthetase inhibitor NG-monomethyl L-arginine produced dose-dependent derepression of the proliferative responses of splenic mononuclear cells to concanavalin A. In contrast, indomethacin and catalase exhibited only weak derepression of the proliferative responses. Subsequent analysis showed that splenic mononuclear cells from spontaneously hypertensive rats generated greater nitric oxide levels than cells from Wistar-Kyoto rats, and nitric oxide levels were reduced when the inhibitor was added to splenic mononuclear cell cultures from spontaneously hypertensive rats. We further demonstrated that L-arginine is required for the development of the depressed mitogen-induced proliferative responses in these cells. Addition of L-arginine in excess of 10 microM to cultures diminished cell proliferation and increased nitric oxide. Polyclonal antibodies to murine interferon gamma reduced nitric oxide accumulation by approximately 50%, suggesting that interferon gamma is partially responsible for enhancing nitric oxide production in mitogen-stimulated splenic mononuclear cell cultures from spontaneously hypertensive rats. Thus, this study provides evidence that the immune depression observed in the spontaneously hypertensive rat is nitric oxide dependent.