Molecular transductional mechanisms by which IFN gamma and other signals regulate macrophage development

Taxol, a microtubule-stabilizing antineoplastic agent, differentially regulates normal and tumor-bearing host macrophage nitric oxide production

Taxol, a potent antitumor chemotherapeutic, promotes in vitro cytotoxic antitumor activities by normal host macrophage (M phi s). Because tumor growth induces functional changes among M phi populations, we determined whether fibrosarcoma growth (Meth-KDE) modified M phi responsiveness to the activating agent taxol. Tumors induce tumor-distal M phi populations to become immune suppressor cells, partially through overproduction of the cytotoxic and proinflammatory molecules nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha). Beneficial to the tumor-bearing host (TBH) when released by tumor-proximal M phi s, NO and TNF-alpha suppress lymphoproliferation and fail to impart antitumor activity when expressed in tumor-distal compartments. We report that taxol differentially regulated normal host and TBH M phi production of the immunosuppressive molecule NO by tumor-distal M phi populations. In response to IFN-gamma-priming and taxol triggering, TBH M phi s increase their production of NO as compared to resting M phi s; however, unlike normal host M phi s, taxol-induced TBH M phi NO production was significantly suboptimal. Modulation of TBH M phi NO production in tumor-distal compartments may alleviate M phi-mediated suppression of T-cell proliferative responses, yet promote sufficient NO production by tumor-associated M phi s to affect cytotoxicity. Collectively, these data leave implications for immunotherapeutic activities by the anticancer drug taxol.

Coexistence of purino- and pyrimidinoceptors on activated rat microglial cells

1. Nucleotide-induced currents in untreated (proliferating) and lipopolysaccharide (LPS; 100 ng ml(-1)) treated (non-proliferating) rat microglial cells were recorded by the whole-cell patch-clamp technique. Most experiments were carried out on non-proliferating microglial cells. ATP (100 nM-1 mM), ADP (10 nM-10 mM) and UTP (1 microM-100 mM), but not uridine (100 microM-10 mM) produced a slow outward current at a holding potential of 0 mV. The effect of UTP (1 mM) did not depend on the presence of extracellular Mg2+ (1 mM). The outward current response to UTP (1 mM) was similar in non-proliferating and proliferating microglia. 2. In non-proliferating microglial cells, the ATP (10 microM)-induced outward current was antagonized by suramin (300 microM) or reactive blue 2 (50 microM), whereas 8-(p-sulphophenyl)-theophylline (8-SPT; 100 microM) was inactive. By contrast, the current induced by UTP (1 mM) was increased by suramin (300 microM) and was not altered by reactive blue 2 (50 microM) or 8-SPT (100 microM). 3. The current response to UTP (1 mM) disappeared when K+ was replaced in the pipette solution by an equimolar concentration of Cs+ (150 mM). However, the effect of UTP (1 mM) did not change when most Cl- was replaced with an equimolar concentration of gluconate (145 mM). The application of 4-aminopyridine (1 mM) or Cs+ (1 mM) to the bath solution failed to alter the UTP (1 mM)-induced current. UTP (1 mM) had almost no effect in a nominally Ca2+-free bath medium, or in the presence of charybdotoxin (0.1 microM); the inclusion of U-73122 (5 microM) or heparin (5 mg ml(-1)) into the pipette solution also blocked the responses to UTP (1 mM). By contrast, the effect of ATP (10 microM) persisted under these conditions. 4. I-V relations were determined by delivering fast voltage ramps before and during the application of UTP (1 mM). In the presence of extracellular Cs+ (1 mM) and 4-aminopyridine (1 mM) the UTP-evoked current crossed the zero current level near -75 mV. Omission of Ca2+ from the Cs+ (1 mM)- and 4-aminopyridine (1 mM)-containing bath medium or replacement of K+ by Cs+ (150 mM) in the pipette solution abolished the UTP current. 5. Replacement of GTP (200 microM) by GDP-beta-S (200 microM) in the pipette solution abolished the current evoked by UTP (1 mM). 6. When the pipette solution contained Cs+ (150 mM) instead of K+ and in addition inositol 1,4,5,-trisphosphate (InsP3; 10 microM), an inward current absolutely dependent on extracellular Ca2+ was activated after the establishment of whole-cell recording conditions. This current had a typical delay, a rather slow time course and did not reverse its amplitude up to 100 mV, as measured by fast voltage ramps. 7. A rise of the internal free Ca2+ concentration from 0.01 to 0.5 microM on excised inside-out membrane patches produced single channel activity with a reversal potential of 0 mV in a symmetrical K+ solution. The reversal potential was shifted to negative values, when the extracellular K+ concentration was decreased from 144 to 32 mM. By contrast, a decrease of the extracellular Cl- concentration from 164 to 38 mM did not change the reversal potential. 8. Purine and pyrimidine nucleotides act at separate receptors in rat microglial cells. Pyrimidinoceptors activate via a G protein the enzyme phospholipase C with the subsequent release of InsP3. The depletion of the intracellular Ca2+ pool appears to initiate a capacitative entry of Ca+ from the extracellular space. This Ca2+ then activates a Ca2+-dependent K+ current.

Endotoxin induces increased intracellular cathepsin B activity in THP-1 cells

Macrophage cathepsin B (CB) is implicated in tissue injury in inflammatory diseases. Lipopolysaccharide (LPS) is an activator of macrophages whose effect on CB is unknown. This study was undertaken to investigate the potential of macrophages as a source of increased CB and to determine if exposure to LPS might stimulate CB levels. As a model we chose the macrophage-like tumor line, THP-1. Incubation with LPS led to a time and dose-dependent increase in CB activity. LPS potentiated interferon-gamma (IFN-gamma)-induced elevations of CB and led to an additive increase in CB activity. Pretreatment of the cells with LPS not only caused a marked stimulation of CB activity over that seen with IFN-gamma alone, but also decreased the concentration and exposure time to the cytokine necessary to achieve maximum induction of the enzyme. The LPS and IFN-gamma induced CB increases were abolished by cycloheximide or actinomycin D in the cultures, indicating that the increases in CB required increased RNA transcription and de novo protein synthesis. Direct measurement of CB mRNA showed increases. These data indicate that although LPS alone appears to induce the production of CB in THP-1 cells, it augments IFN-gamma induced increases, suggesting that two signals are necessary for maximum CB induction in this system.

Cytokines and the pathogenesis of myasthenia gravis

Myasthenia gravis (MG) and its animal model experimental autoimmune myasthenia gravis (EAMG) are caused by autoantibodies against nicotinic acetylcholine receptor (AChR) in skeletal muscle. The production of anti-AChR antibodies is mediated by cytokines produced by CD4+ and CD8+ T helper (Th) cells. Emerging investigations of the roles of cytokines in MG and EAMG have revealed that the Th2 cell related cytokine interleukin 4 (IL-4), an efficient growth promoter for B-cell proliferation and differentiation, is important for anti-AChR antibody production. IL-6 and IL-10 have similar effects. The Th1 cytokine IFN-gamma is important in inducing B-cell maturation and in helping anti-AChR antibody production and, thereby, for induction of clinical signs and symptoms. Results from studies of time kinetics of cytokines imply that IFN-gamma is more agile at the onset of EAMG, probably being one of the initiating factors in the induction of the disease, and IL-4 may be mainly responsible for disease progression and persistance. Even though other Th1 cytokines like IL-2, tumor necrosis factor alpha (TNF-alpha), and TNF-beta as well as the cytolytic compound perforin do not directly play a role in T-cell-mediated help for anti-AChR antibody production, they are actually involved in the development of both EAMG and MG, probably by acting in concert with other cytokines within the cytokine network. In contrast, transforming growth factor beta (TGF-beta) exerts immunosuppressive effects which include the down-regulation of both Th1 and Th2 cytokines in MG as well as EAMG. Suppressive effects are also exerted by interferon alpha (IFN-alpha). Based on elucidation of the role of cytokines in EAMG and MG, treatments that up-modulate TGF-beta or IFN-alpha and/or suppress cytokines that help B-cell proliferation could be useful to improve the clinical outcome.

Antitumor vaccination with gene-transduced tumor cells expressing a fusion protein RM4/IFN-tau

Our previous studies showed that secretion of a fusion protein RM4/IFN-tau from a mouse myeloma cell line VKCK/RM4-IFN-tau curtailed its tumorigenicity. Inoculation of VKCK/RM4-IFN-tau tumor cells further induced a protective immunity against a secondary challenge of parental VKCK tumor cells, in which the predominant immune cellular components are CD8+ T cells. In this study, VKCK/RM4-IFN-tau cell line was again used to further characterize the protective immunity. We found that the reduced tumorigenicity of VKCK/RM4-IFN-tau was directly related to the amount of fusion protein secreted by tumor cells, and that CD8+ T cells derived from mice experienced with VKCK/RM4-IFN-tau tumor regression played an important role in the protective immunity in a chromium release assay in vitro and in an animal study in vivo by using T-cell subset depleted mice. Our animal studies also showed that not only the cytotoxic but also the memory T cells against the secondary challenge of parental VKCK cells could be adoptively transferred to normal BALB/c mice. In addition, our animal studies further showed that local vaccination of irradiated VKCK/RM4-IFN-tau cells was able to significantly inhibit established tumors in early stages in vivo. This study thus highlights the potential utility of this engineered VKCK/RM4-IFN-tau tumor cells secreting the fusion protein RM4/IFN-tau in cancer gene therapy.

Competitive PCR quantification of pro- and anti-inflammatory cytokine mRNA in the central nervous system during autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the central nervous system that can be induced by immunization with myelin basic protein (MBP)/complete Freund's adjuvant and serves as a model for multiple sclerosis. Recent studies have suggested that cytokines play a crucial role in the clinical course of EAE. To clarify the roles of cytokines in EAE, we examined levels of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta1 (TGF-beta1) and interleukin-10 (IL-10) mRNA in isolates from infiltrating inflammatory cells in EAE lesions induced in Lewis rats. The non-radioactive and sensitive competitive PCR method was employed to quantify the relative amounts of cytokine mRNA. Levels of both IFN-gamma and TNF-alpha mRNA were increased at the early stage of EAE and rapidly decreased at the peak stage. On the other hand, TGF-beta1 mRNA was demonstrated throughout the course of EAE as well as under normal conditions and its amount paralleled the severity of EAE. IL-10 mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR) under normal conditions, but was below the level of detection of competitive PCR. IL-10 mRNA expression peaked at the early stage of EAE and declined gradually thereafter. Taken together, these results suggest that IFN-gamma and TNF-alpha might play a crucial role in the development of EAE. Furthermore, it appears that the peak expression of IL-10 mRNA at the early stage and the following marked TGF-beta1 expression at the peak stage might represent an important endogenous mechanism to limit the extent of inflammation and to prevent relapse in the course of acute monophasic EAE.

Linomide suppresses both Th1 and Th2 cytokines in experimental autoimmune myasthenia gravis

Suppressive effects of the synthetic immunomodulatory drug Linomide have been shown in several autoimmune models, including antibody-mediated experimental autoimmune myasthenia gravis (EAMG), a model for human myasthenia gravis (MG). To define the mechanisms underlying EAMG suppression, we injected Linomide subcutaneously at different doses into Lewis rats immunized with Torpedo acetylcholine receptor (AChR) in complete Freund's adjuvant (CFA), and investigated AChR-specific T and B cell responses, and the levels of lymph node cells expressing mRNA of different cytokines after AChR stimulation in vitro. Both 160 and 16, but not 1.6, mg/kg/day of Linomide effectively suppressed clinical muscle weakness, accompanied by decreased AChR-induced T and B cell responses. Linomide also suppressed the mRNA expression of the Th1 cytokines IFN-gamma, IL-12 and TNF-alpha as well as the Th2 cytokines IL-4 and IL-10, which are important in the immunopathogenesis of EAMG by promoting antibody production. There were no differences for IL-1beta, IL-6, lymphotoxin or TGF-beta expression in Linomide-treated vs nontreated control EAMG rats. We conclude that Linomide suppresses clinical EAMG as well as B and T cell responses to AChR by counteracting the production of AChR-induced Th1 and Th2 cytokines.

The effect of immunomodulation of stimulator antigen presenting cells on subsequent responder T-cell function

In this study, we examined whether lipopolysaccharide (LPS)-, interferon-gamma (IFN-gamma) or 16,16-dimethyl prostaglandin E2 (dmPGE2)-pretreatment of stimulator spleen cells from C57BL6 (B6) mice affects effector function of responder T-lymphocyte from C3H/HeJ mice. Stimulation of B6-derived splenic mononuclear cells (SMNCs) with LPS (10 micrograms/ml) prior to their utilization as stimulator cells in a mixed lymphocyte culture (MLC) resulted in an increase in responder T-lymphocyte proliferation compared to utilization of unstimulated SMNC (P < 0.05). IFN-gamma demonstrated similar effects in a dose dependent fashion with maximal stimulatory effect seen at 1000 U/ml. In contrast, pretreatment of stimulator SMNC with dmPGE2 resulted in dose-dependent inhibition of the responder T-lymphocyte proliferation with maximum inhibitory effect seen using a concentration of dmPGE2 of 10(-5) M. The presence of indomethacin in the MLC did not reverse this effect. These data demonstrate the effect of immunomodulation of stimulator spleen cells on subsequent T-lymphocyte function.

Major histocompatibility complex regulation of cytokine production

This review describes the phenomenon of the major histocompatibility complex (MHC) control of cytokine production both in experimental animals and in humans. H-2 (mouse MHC) regulates which type of cytokine is selectively produced in response to the hapten trinitrophenyl (TNP). T cells from TNP-immune H-2k mice produce interferon-gamma (IFN-gamma), interleukin-2 (IL-2), IL-3, IL-5, tumor necrosis factor-alpha (TNF-alpha), IL-10, and very low levels of IL-4 on reexposure to the specific antigen in vitro. By contrast, T cells from H-2d mice produce IL-3, TNF-alpha, IL-10, and IL-4 but very low levels of IL-2, IL-5 and IFN-gamma. As MHC-congenic matched strains (BALB/k and BALB/c) are used, this makes it unlikely that non-MHC genes influence the class of response observed. A similar pattern of haplotype regulation of cytokine production is observed in humans. In fact, peripheral blood mononuclear cells from HLA-B8,DR3-positive and negative individuals differ in their ability to produce IL-2, IL-5, and IFN-gamma on stimulation with the mitogen phytohemagglutinin while producing similar amounts of IL-4, IL-6, and IL-10. The following main considerations emerge from these observations. The MHC/peptide complex generated after antigen immunization, indicates which class of cytokine production is preferentially induced and, therefore, the outcome of the immune response. Furthermore, MHC genotype may affect cytokine production (and then immune responses) by completely different mechanism(s), that is, by an antigen-nonspecific control that does not depend on the ability of MHC molecules to bind in different ways the different peptides. Accurate control of the functional repertoire of an immune response is a critical parameter in response to infections as well as in immunopathology. MHC control of the class of the immune response at the level of cytokine production is a sophisticated way in which this occurs. This control might be involved in adaptive immune responses to infections as well as in immunopathology.

Activation of a mouse macrophage cell line by acemannan: the major carbohydrate fraction from Aloe vera gel

Acemannan is the name given to the major carbohydrate fraction obtained from the gel of the Aloe vera leaf. It has been claimed to have several important therapeutic properties including acceleration of wound healing, immune stimulation, anti-cancer and anti-viral effects. However, the biological mechanisms of these activities are unclear. Because of this wide diversity of effects, it is believed that they may be exerted through pluripotent effector cells such as macrophages. The effects of acemannan on the mouse macrophage cell line, RAW 264.7 cells were therefore investigated. It was found that acemannan could stimulate macrophage cytokine production, nitric oxide release, surface molecule expression, and cell morphologic changes. The production of the cytokines IL-6 and TNF-alpha were dependent on the dose of acemannan provided. Nitric oxide production, cell morphologic changes and surface antigen expression were increased in response to stimulation by a mixture of acemannan and IFN-gamma. These results suggest that acemannan may function, at least in part, through macrophage activation.

Autoreactive T cell responses and cytokine patterns reflect resistance to experimental autoimmune myasthenia gravis in Wistar Furth rats

Various mouse and rat strains show different susceptibilities to experimental autoimmune myasthenia gravis (EAMG) that can be induced by immunization with acetylcholine receptor (AChR) and Freund's complete adjuvant, and represents a model for the antibody-mediated myasthenia gravis in humans. We examined AChR-induced B and T cell responses and cytokine mRNA expression to study the mechanisms behind susceptibility to EAMG in Lewis rats and resistance in Wistar Furth (WF) rats. Both strains had similarly elevated concentrations and affinities of serum anti-AChR antibodies, and no difference between the two strains for frequencies of cells in lymphoid organs expressing mRNA of the B cell stimulating cytokine interleukin-4 was found. In contrast, T cell responses to AChR measured by proliferation and by enumeration of interferon-gamma-expressing cells at both mRNA and protein level were lower in the resistant WF rats. This strain showed, instead, an up-regulation of the anti-inflammatory transforming growth factor-beta. Strain-related differences in the susceptibility to actively induced EAMG are thus related to quantitative differences in distribution between pro-inflammatory and anti-inflammatory cytokines.

Mouse myeloma cell line secreting bifunctional fusion protein RM4/IFN-gamma [corrected] elicits antitumor CD8 MHC class I-restricted T cells that are cytolytic in vitro and tumoricidal in vivo

Mouse myeloma cell line VKCK/RM4-IFN-gamma secreting the bifunctional fusion protein RM4/IFN-gamma was used to study the relationship between IFN-gamma secretion of tumor cells and its tumorigenicity and to study the potential mechanism responsible for the immune response. IFN-gamma secretion of VKCK/RM4-IFN-gamma tumor cells was estimated at 90 U/ml using an antiviral assay. To evaluate tumorigenicity, 5 x 10(5) viable IFN-gamma-secreting VKCK/RM4-IFN-gamma and non-IFN-gamma-secreting VKCK tumor cells were injected s.c. into syngeneic BALB/c mice and VKCK/RM4-IFN-gamma-immunized or T cell subset-depleted BALB/c mice, respectively. Tumor progression or regression was evaluated 2 weeks after tumor inoculation. Our animal studies showed that RM4/IFN-gamma secretion by VKCK/RM4-IFN-gamma tumor cells curtailed its tumorigenicity in BALB/c mice and induced a persistant protective immune response against a subsequent graft of parental VKCK tumor. This protective immunity is long term and tumor specific as measured in a 51Cr-release assay. In addition, our animal studies in T cell subset-depleted BALB/c mice showed that CD8 CTL play a major role in the reduction of tumorigenicity. This study thus highlights the potential advantages of localized IFN-gamma in tumors to induce potent antitumor immunity and further suggests that the bifunctional fusion protein RM4/IFN-gamma may be useful in cancer immunotherapy because of its capacity of targeting IFN-gamma to human tumors expressing the human tumor-associated TAG72 antigen [corrected].

Cytokines in relapsing experimental autoimmune encephalomyelitis in DA rats: persistent mRNA expression of proinflammatory cytokines and absent expression of interleukin-10 and transforming growth factor-beta

Experimental autoimmune encephalomyelitis (EAE) in rats is typically a brief and monophasic disease with sparse demyelination. However, inbred DA rats develop a demyelinating, prolonged and relapsing encephalomyelitis after immunization with rat spinal cord in incomplete Freund's adjuvant. This model enables studies of mechanisms related to chronicity and demyelination, two hallmarks of multiple sclerosis (MS). Here we have investigated, in situ, the dynamics of cytokine mRNA expression in the central nervous system (CNS) and peripheral lymphoid organs (lymph node cells and splenocytes) of diseased DA rats. We demonstrate that peripheral lymphoid cells stimulated in vitro with encephalitogenic peptides 69-87 and 87-101 of myelin basic protein responded with high mRNA expression for proinflammatory cytokines; interferon-gamma, interleukin-12 (IL-12), tumour necrosis factors alpha and beta, IL-1 beta and cytolysin. A high expression of mRNA for these proinflammatory cytokines was also observed in the CNS where it was accompanied by classical signs of inflammation such as expression of major histocompatibility complex class I and II, CD4, CD8 and IL-2 receptor. The expression of mRNA for proinflammatory cytokines was remarkably long-lasting in DA rats as compared to LEW rats which display a brief and monophasic EAE. Furthermore, mRNAs for putative immunodownmodulatory cytokines, i.e. transforming growth factor-beta (TGF-beta), IL-10 and IL-4 were almost absent in DA rats, in both the CNS and in vitro stimulated peripheral lymphoid cells, while their levels were elevated in the CNS of LEW rats during the recovery phase. We conclude that the MS-like prolonged and relapsing EAE in DA rats is associated with a prolonged production of proinflammatory cytokines and/or low or absent production of immunodownmodulatory cytokines.

Effect of gamma interferon on expression of Fc gamma receptors in monocytes of newborn infants and adults

Fc gamma receptors provide an essential link between cellular and humoral immunity, and little is known about their expression in monocytes of newborn infants. We compared baseline and gamma interferon (IFN-gamma)-induced expression of Fc gamma RI and Fc gamma RII protein and Fc gamma RI mRNA in monocytes from healthy, term infants and adults. Fluorescence-activated cell sorter analysis demonstrated that baseline expression of monocyte Fc gamma RI in newborn infants was not significantly different from that in adults, while Fc gamma RII protein expression in monocytes derived from newborns was significantly higher than that for adults (mean channel fluorescence [MCF] for newborns and adults, 5.53 and 4.50, respectively [P = 0.039]). In vitro treatment with recombinant IFN-gamma increased the expression of Fc gamma RI in monocytes of newborns and adults to the same extent (2.4- and 2.2-fold increase in MCF in newborns and adults, respectively, at 42 h). We developed a semiquantitative fluorescence reverse transcriptase PCR which demonstrated a significant increase in mRNA for Fc gamma RI in monocytes of newborns and adults with in vitro IFN-gamma exposure, indicating that IFN-gamma acts by increasing the transcription or transcript stability of Fc gamma RI mRNA. While there was no significant effect of IFN-gamma treatment on Fc gamma RII expression in monocytes from adults, there was a 20% increase in Fc gamma RII in monocytes from newborns (P = 0.009). Monocytes from healthy, term newborns and adults exhibit comparable baseline and IFN-gamma-induced levels of expression of Fc gamma RI and higher baseline and IFN-gamma-induced levels of expression of Fc gamma RII.

Immunological memory induced by genetically transduced tumor cells

BACKGROUND

Recent studies have demonstrated the usefulness of gene-modified tumor cells for immunotherapy. Using the tumorigenic murine fibrosarcoma, MCA 106, we investigated the effects of localized interferon-gamma (IFNg) secretion on tumorigenicity and on long-term memory.

METHODS

The murine IFNg (MuIFNg) gene was introduced into tumor cells. High and low IFNg-secreting clones were isolated. C57BL/6 mice were injected subcutaneously (s.c.) with either parental (P), high or low IFNg-secreting (H- or L-IFNg) cells, and tumor growth was assessed weekly. Spleens were harvested on different days postinjection (p.i.) to assess in vitro cytolytic activity. In parallel, tissues from injection sites were stained with macrophage-, CD4-, and CD8-detecting antibodies. Mice were injected s.c. with H-IFNg MCA106 tumor. After 150 days the animals were rechallenged s.c. with MCA106P in one leg and with irrelevant syngeneic tumor in the other.

RESULTS

Both P- and L-IFNg cells had similar growth, whereas the H-IFNg cells never grew. Only splenocytes from the H-IFNg animals showed in vitro CTL activity persisting until day 30 p.i. Histological data revealed a macrophage and CD4+ infiltrate much earlier in the H-IFNg group compared with the P group. Only the irrelevant, syngeneic tumor grew in animals previously injected with H-IFNg cells, whereas both P and irrelevant syngeneic tumors grew in controls.

CONCLUSIONS

Transduction of MCA106 cells with the MuIFNg gene diminished in vivo tumorigenicity in proportion to the amount of IFNg secreted. Immunization with H-IFNg cells elicited a host response characterized by macrophages and CD4+ cells. Long-term tumor-specific memory was seen after immunization with H-IFNg cells.

Temporal regulation by adrenergic receptor stimulation of macrophage (M phi)-derived tumor necrosis factor (TNF) production post-LPS challenge

Macrophage (M phi) responsiveness can be regulated by various mediators, including those which emanate from, and mimic, the sympathetic nervous system. Whereas beta-adrenergic agonists suppress, alpha 2-adrenergic agonists augment lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF) production and gene expressed. The susceptibility of M phi s to regulation of LPS-induced TNF production and mRNA accumulation was examined following beta-adrenergic and alpha 2-adrenergic receptor activation at specific time points post-LPS challenge. Complete Freund's adjuvant-elicited murine M phi s were incubated with LPS (30 ng/ml) in the presence or absence of adrenergic agonists or antagonists. We assessed the susceptibility of immunologically-activated M phi s to adrenergic receptor regulation: a) during the 1 h delay in the production of TNF after LPS-stimulation, and b) during the rapid increase in TNF production which follows. Disparate responsiveness of M phi s to adrenergic drugs was observed during this time course of TNF production and TNF mRNA accumulation. In particular, while the concomitant addition of an alpha 2-adrenergic antagonist and LPS resulted in 45% suppression of TNF production, this selective blockade of alpha 2-adrenergic receptors on M phi s was equally effective throughout the first 45 min post-LPS challenge. After this initial period, the alpha 2-adrenergic receptor became progressively less responsive as demonstrated by the delayed addition of yohimbine (10(-5) M) post-LPS challenge. The addition of the selective alpha 2-adrenergic agonist UK-14304 (10(-7) M) to LPS-activated M phi s augmented TNF mRNA accumulation. However, this augmentation was even greater when the addition of the alpha 2-adrenergic agonist was delayed post-LPS challenge. It was also shown that the beta-adrenergic agonist isoproterenol (10(-6) M) produced maximum suppression of TNF production within the first 1.5 h post-LPS challenge. Suppression by isoproterenol (10(-6) M) of TNF mRNA accumulation occurred throughout the 2-h period assessed post-LPS stimulation of M phi s. The decline in isoproterenol-induced regulation was accompanied by an elevation in beta 2-adrenergic receptor mRNA accumulation. Furthermore, suppression of TNF production induced by a maximum concentration of isoproterenol was observed at various LPS concentrations (0.001-1000 ng/ml), although this was not as pronounced a suppression as demonstrated for dibutyrl cAMP. These results demonstrate that the susceptibility of M phi s to adrenergic receptor regulation changes throughout the time period necessary for gene activation and ultimate release of TNF. Thus, the production of TNF during LPS-dependent disease states may be regulated by adrenergic mediators throughout different temporal windows, better explaining the role played by the nervous system.

Cytokine production pathway in the elderly

It is well known that aging is associated with various alterations in lymphoid cell functions, particularly with a progressive decline in immune responsiveness to exogenous antigens and increasing incidence of autoimmune phenomena. Many studies have been focused on the mechanisms of the immunologic features of aging. this review describes our results of studies performed to determine the influence of age on the capacity to produce interleukin-2 (IL-2), interferon-gamma (IFN-gamma), interleukin-4 (IL-4), interleukin-t (IL-5), interleukin-6 (IL-6) and tumor necrosis factor (TNF). Mitogen-stimulated cultures of mononuclear cells (MNC) from human beings were assessed for cytokine-producing capacity. A significant decrease in IFN-gamma and IL-2 production by MNC cultures from elderly individuals was observed. No significant difference was instead observed between cultures from elderly individuals and those from young ones as regards TNF-alpha, IL-4 and IL-6 production. Mitogen or antigen-stimulated cultures of MNC from aged mice also displayed a significant decrease in IFN-gamma and IL-2 production as well as TNF-beta. Instead IL-4 and IL-5 production significantly increased in these cultures. We suggest that this imbalanced cytokine production may well account for the pattern of immune response which may be observed in the elderly, i.e. a normal or increased humoral response (including autoimmune responses) in face of a low T cell immune responsiveness.

Proinflammatory cytokines can significantly induce human mononuclear phagocytes to produce nitric oxide by a cell maturation-dependent process

The capacity of three proinflammatory cytokines, interferon-gamma (rhifn-gamma), tumour-necrosis factor-alpha (rHTNF-alpha) and interleukin-1 (rHIL-1), to induce release of nitric oxide (NO) from human mononuclear phagocytes were investigated. Peripheral blood monocytes were either used immediately or after culturing in vitro to develop into monocyte-derived macrophages (macrophages). Lipopolysaccharide (LPS) was used as second signal in all experiments. The three cytokines tested had significantly high enhancing influence on the production of nitric oxide by monocytes as well as by macrophages. However production was significantly higher by the monocytes matured in vitro to macrophages (P < 0.01). In our experimental system LPS had only marginal synergistic influence on production of NO2, and IFN-gamma demonstrated to be the most efficient of the three cytokines tested. Addition of L-arginine in the monocytes/macrophages culture further amplified production of NO2, whereas addition of NG-monomethylarginine abrogated this amplification. We conclude that human mononuclear phagocytes are capable of using inducible nitric oxide synthase pathway to produce nitric oxide.

Effect of adrenaline and phorbol myristate acetate or bacterial lipopolysaccharide on stimulation of pathways of macrophage glucose, glutamine and O2 metabolism. Evidence for cyclic AMP-dependent protein kinase mediated inhibition of glucose-6-phosphate dehydrogenase and activation of NADP+-dependent 'malic' enzyme

Adrenaline has recently been shown to stimulate both glucose metabolism and H2O2 release by macrophages but the activity of the key pentose phosphate pathway enzyme, glucose-6-phosphate dehydrogenase (which generates the NADPH crucial for the reduction of molecular oxygen), was reduced under these conditions [Costa Rosa, Safi, Cury and Curi (1992) Biochem. Pharmacol. 44, 2235-2241]. We report here that adrenaline activates another NADPH-producing enzyme, NADP(+)-dependent 'malic' enzyme, while also inhibiting glucose-6-phosphate dehydrogenase, via cyclic AMP-dependent protein kinase (PKA) activation. Regulation of glucose-6-phosphate dehydrogenase activity by PKA has not been reported elsewhere. The sparing of some glucose from pentose phosphate pathway consumption may be important in the provision of glycerol 3-phosphate which in the macrophage may be required for new phospholipid synthesis. Glutamine oxidation was also stimulated by adrenaline thus providing increased substrate (malate) for NADP(+)-dependent 'malic' enzyme and therefore shifting some of the burden of NADPH production from glucose to glutamine metabolism. We also report a novel synergistic effect of adrenaline and some bacterial products and/or gamma-interferon in stimulating secretory and metabolic pathways in macrophages which may be a part of a larger network of signals that lead to enhanced macrophage activity.

The outer surface proteins of Lyme disease borrelia spirochetes stimulate T cells to secrete interferon-gamma (IFN-gamma): diagnostic and pathogenic implications

Late stages of borrelia Lyme disease infections may be difficult to diagnose because of unspecific symptoms and unreliable laboratory tests, being too unspecific or insensitive. The T cell immune response was thus evaluated in these patients by using a sensitive ELISPOT T cell assay that detects the secretion of IFN-gamma, i.e. a T helper 1 (Th1) response on the single-cell level. Three subcellular fractions of the Lyme borreliosis strain Borrelia afzelii were used for antigenic stimulation. The outer surface protein (Osp) fraction elicited the strongest response, discriminating between borrelia infections (n = 15) compared with other neurological diseases (n = 10) and normal controls (n = 12) (P = 0.0001). The more heterogeneous sonicated borrelia fraction also elicited a strong response, however, also in some of the controls. The flagellin fraction did not have a similar T cell-stimulating effect. When looking at subgroups of borrelia infections, central nervous system (CNS) infections (n = 7) revealed a lower T cell response in blood (P = 0.0128) compared with other borrelia manifestations (n = 8). Cerebrospinal fluid (CSF) lymphocytes were available from three patients with CNS borreliosis, and all showed a compartmentalization with higher responses to the Osp fraction in CSF compared with blood, also in the two patients without any intrathecal-specific antibody synthesis. The ELISPOT method is feasible for detecting a specific IFN-gamma T cell response in borrelia infections. This Th1 response may well be of pathogenic relevance.

Differential expression of novel genes by bone marrow-derived macrophage populations

In the present study, we have constructed a subtraction cDNA library to identify novel genes induced by IFN-gamma in GM-CSF-derived bone marrow macrophage (m phi). M theta were treated with 50 U/ml IFN-gamma for 40, 70 and 140 min to induce expression of early genes regulated by IFN-gamma, and the M phi were pooled. Poly(A)+RNA was prepared from both unactivated and IFN-gamma-stimulated m theta, and cDNA libraries were constructed in lambda ZAP. Genes expressed in common by both m theta populations were removed by subtraction using biotin-avidin precipitation of hybrid complexes. Further selection was performed by differential screening using cDNA prepared from mRNA of unactivated m phi as a probe, followed by colony hybridization to remove sister clones. Of 17 clones from which sequence information was obtained, two appeared to be identical with the murine genes, C10 (clone GM2B1) and Mac-2 (clone GM2C4) and an additional two clones had high similarity to human cDNAs encoding proteins of unknown function. cDNAs containing sequences which did not match published sequences were used to probe Northern blots prepared from both unstimulated and IFN-gamma-activated GM-CSF- and CSF-1-derived m phi. Five clones (GM1A2, GM1B4, GM1F2, GM2A12 and GM2B8) showed enhanced transcript levels following IFN-gamma treatment of GM-CSF-derived m phi, but demonstrated high constitutive transcript levels in CSF-l-derived m phi. In addition, C10 transcripts were constitutively expressed by GM-CSF-derived m phi, but not by CSF-1-derived m phi, even after activation by IFN-gamma. These data suggest that much of the functional heterogeneity of GM-CSF- and CSF-1-derived m phi resides in the differential expression of early genes specifically induced by IFN-gamma.

The inhibitory effects of Mycobacterium tuberculosis on MHC class II expression by monocytes activated with riminophenazines and phagocyte stimulants

The expression of MHC class II antigens by peripheral blood monocytes from normal individuals was investigated. Class II expression as determined by a cell ELISA was effectively induced by various phagocyte stimulants. A further aspect of our study investigated the effects of clofazimine, a riminophenazine antimicrobial agent and its analogue, B669, on class II expression. Both agents at concentrations attainable in vivo increased the expression of MHC class II antigens. A 25-kD glycolipoprotein derived from Mycobacterium tuberculosis that inhibits phagocyte functions has previously been described. This component significantly reduced the expression of MHC class II antigens induced by the riminophenazines, clofazimine and B669, interferon-gamma (IFN-gamma) or opsonised yeast when added at the initiation of experiments. The riminophenazines could not restore the decrease in class II antigen expression previously inhibited by the 25-kD mycobacterial fraction. However, cultures prestimulated with the riminophenazines or phagocyte stimulants were unaffected by the 25-kD mycobacterial fraction. The results suggest the potential use of these agents as modulators of phagocyte function.

Qualitative and quantitative analysis of T lymphocytes during normal human pregnancy

PROBLEM

Human reproduction involves contact between cells which are allogeneic to one another, however the fetus not only survives but thrives.

METHODS

Aspects of T-cell-mediated immunity during normal human pregnancy were studied. PBMNCs of pregnant and nonpregnant women were stimulated with PHA and cytomegalovirus antigens (CMV). The capacity of stimulated cells to proliferate, to produce IL-2 and IFN-gamma, to express IL-2 receptor (IL2R1) and the effect of rIL2 on the proliferation rate of lymphocytes were examined. FACS was utilized for T-cell subset comparisons.

RESULTS

The proliferation rate, IL-2, and IFN-gamma synthesis were all significantly impaired at suboptimal concentration of PHA throughout pregnancy. Exogenous rIL-2 corrected this depression of cell-mediated immunity (CMI). At optimal concentration of PHA, proliferation rate and production of IFN-gamma and IL-2 were all decreased. Exogenous rIL-2 corrected these deficits only in the third trimester. Third trimester pregnant women demonstrated a significant depression of proliferation as well as IL-2 and IFN-gamma production after CMV stimulation, which was partially corrected by exogenous rIL-2. FACS analysis suggested that after stimulation by CMV and optimal concentration of PHA, T cells were activated and both CD4+ and CD8+ lymphoblasts expressed normal density of IL-2R1. With suboptimal PHA, the number of activated CD4+ and CD4+IL2R1+ cells were diminished and CD4+ and CD8+ T lymphoblasts expressed lower number of IL2R1.

CONCLUSIONS

CD4 T helper (Th1) cell function is down regulated progressively during the three trimesters of pregnancy without changes in the quantity of T cell subsets.

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

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

Interferon gamma, interleukin 4 and transforming growth factor beta in experimental autoimmune encephalomyelitis in Lewis rats: dynamics of cellular mRNA expression in the central nervous system and lymphoid cells

The potential role of certain important immunoregulatory and effector cytokines in autoimmune neuroinflammation have been studied. We have examined the expression of mRNA, with in situ hybridization, of interferon gamma (IFN-gamma), interleukin 4 (IL-4) and transforming growth factor beta (TGF-beta) both in sections of spinal cords and the antigen-induced expression of these cytokines by lymphoid cells after stimulation with a dominant encephalitogenic peptide of MBP (MBP 63-88) during the course of actively induced experimental autoimmune encephalomyelitis (EAE) in Lewis rats. In spinal cords, the target organ in EAE, cells expressing mRNA for IFN-gamma, first appeared at the onset of clinical signs, i.e., day 10 postimmunization (p.i.), peaked at the height of disease (day 13 p.i.) and then gradually decreased concomitant with recovery. Very few IL-4 mRNA-expressing cells appeared in the spinal cord with no clear relation to clinical signs or histopathology. In contrast, expression of mRNA for TGF-beta did not increase until day 13 p.i., at height of the disease, shortly preceding recovery. These data are consistent with a disease upregulating role of IFN-gamma, while TGF-beta may act to limit central nervous system (CNS) inflammation. In lymphoid organs, primed MBP 63-88 reactive T cells showed an interesting time-dependent evolution of their cytokine production in vitro. Thus, early after immunization there was a conspicuous MBP 63-88-induced production of both IFN-gamma and IL-4. Such cells may act in the initiation and promotion of the disease. Later, in the recovery phase, MBP 63-88 induced lymphoid cells to TGF-beta production. Thus, an autoantigen-specific production of TGF-beta occurred during EAE and hypothetically such a mechanism may serve to downregulate aggressive autoimmunity systemically.

Targeted disruption of the NF-IL6 gene discloses its essential role in bacteria killing and tumor cytotoxicity by macrophages

To investigate the role of NF-IL6 in vivo, we have generated NF-IL6 (-/-) mice by gene targeting. NF-IL6 (-/-) mice were highly susceptible to infection by Listeria monocytogenes. Electron microscopic observation revealed the escape of a larger number of pathogens from the phagosome to the cytoplasm in activated macrophages from NF-IL6 (-/-) mice. Furthermore, the tumor cytotoxicity of macrophages from NF-IL6 (-/-) mice was severely impaired. However, cytokines involved in macrophage activation, such as TNF and IFN gamma, were induced normally in NF-IL6 (-/-) mice. Nitric oxide (NO) formation was induced to a similar extent in macrophages from both wild-type and NF-IL6 (-/-) mice. These results demonstrate the crucial role of NF-IL6 in macrophage bactericidal and tumoricidal activities as well as the existence of a NO-independent mechanism of these activities. We also demonstrate that NF-IL6 is essential for the induction of G-CSF in macrophages and fibroblasts.

Cellular mRNA expression of interferon-gamma, IL-4 and transforming growth factor-beta (TGF-beta) by rat mononuclear cells stimulated with peripheral nerve myelin antigens in experimental allergic neuritis

Experimental allergic neuritis (EAN) serves as a useful model for inflammation in the peripheral nervous system. To study the potential role of important immunoregulatory and effector cytokines in EAN, we examined the expression of mRNA for interferon-gamma (IFN-gamma), IL-4 and TGF-beta by in situ hybridization in lymph node and splenic cells cultured with bovine peripheral nerve myelin (BPM), P2 and P0 during the course of EAN in Lewis rats. Levels of IFN-gamma mRNA-expressing mononuclear cells (MNC) from lymph nodes and spleens roughly correlated with clinical status, consistent with a disease-promoting role for IFN-gamma. BPM, P0 and P2-reactive IFN-gamma mRNA-expressing T cells appeared in lymph nodes and spleen before onset of the disease, whereas a significant TGF-beta response to BPM, P2 and P0 was observed at lower levels than the IFN-gamma response and at onset of recovery, consistent with a disease down-regulating role of TGF-beta. IL-4 mRNA-expressing cells were found at levels similar to TGF-beta mRNA-expressing cells, and with the latest peak of the three cytokines examined. This result suggests that IL-4 may also suppress IFN-gamma expression at late recovery phase of EAN.

Macrophage priming and activation during fibrosarcoma growth: expression of c-myb, c-myc, c-fos, and c-fms

Macrophages (M phi)3 function by a two-step process that includes priming (induction of cytokine and enzyme mRNA) and activation (production of effector molecules). The initial steps in M phi priming involve the expression of certain proto-oncogenes that regulate expression of other genes. Because tumor growth primes M phi to produce several suppressor monokines, we determined if cancer induced M phi expression of these proto-oncogenes. Unstimulated peritoneal M phi from tumor-bearing hosts (TBH) constitutively expressed the proto-oncogenes c-fms, c-fos, c-myc, and c-myb, whereas normal host (NH) M phi had little or no expression of these proto-oncogenes. When M phi were given a 24-h adherence priming stimulus, NH M phi expressed c-fms and c-fos at levels equivalent to TBH M phi constitutive expression. Adherence had little or no effect on c-fms and c-fos expression in TBH M phi or on NH and TBH M phi c-myc expression. c-myb expression was not induced in NH M phi during adherence and was strongly decreased in TBH M phi. Activation with a 1-h lipopolysaccharide-treatment increased NH and TBH M phi expression of c-fms, c-fos, and c-myc, with higher expression of these proto-oncogenes in TBH M phi. Activation failed to induce c-myb expression in NH M phi and completely inhibited expression in TBH M phi. Because c-fms, c-fos, and c-myc are normally expressed early during M phi activation, our results suggest that tumor growth primes M phi by inducing expression of these proto-oncogenes. c-myb is expressed in immature M phi and is downregulated during M phi activation. These observations explain why NH M phi expression of c-myb was not induced and are consistent with reports that suggest TBH M phi have not reached full developmental maturity. The induction of M phi proto-oncogene expression during cancer may put M phi in a primed state, which leads to earlier and stronger production of adverse suppressor and cytotoxic molecules.

Increased transforming growth factor-beta, interleukin-4, and interferon-gamma in multiple sclerosis

The inflammatory nature of multiple sclerosis (MS) implicates the participation of immunoregulatory cytokines, including the T-helper type 1 (Th1) cell-associated interferon-gamma (IFN-gamma), the Th2 cell-related interleukin-4 (IL-4), and the immune response-downregulating cytokine transforming growth factor-beta (TGF-beta), but proof for their involvement in MS has been lacking. By adopting in situ hybridization with complementary DNA oligonucleotide probes for human IFN-gamma IL-4, and TGF-beta, the expression of mRNA for these cytokines was detected in mononuclear cells (MNC) from blood and cerebrospinal fluids. Strongly elevated levels of MNC expressing all three cytokines were found in peripheral blood and at even higher frequencies in cerebrospinal fluid from untreated patients with MS and optic neuritis, i.e., a common first manifestation of MS, compared with patients with other neurological diseases and healthy subjects. In MS and optic neuritis, IL-4 mRNA expressing cells predominated, followed by TGF-beta- and IFN-gamma-positive cells. Control patients with myasthenia gravis had similarly elevated levels of IFN-gamma and TGF-beta and TGF-beta mRNA expressing blood MNC but lower numbers of IL-4-positive cells. No or slight disability of MS was associated with high levels of TGF-beta mRNA expressing cells, while MS patients with moderate or severe disability had high levels of IFN-gamma-positive cells. IFN-gamma and TGF-beta may have opposing effects in MS, and treatments inhibiting IFN-gamma and/or promoting TGF-beta might ameliorate MS.

Characterization and transduction mechanisms of purinoceptors in activated rat microglia

1. Purinoceptor agonist-induced currents in untreated (proliferating) and lipopolysaccharide- (LPS; 100 ng ml-1) treated (non-proliferating) rat microglial cells were recorded by the whole-cell patch-clamp technique. 2. In non-proliferating microglia, adenosine (0.01-100 microM), 2-methylthio ATP (3-3000 nM), ATP (0.1-1000 microM), and ATP-gamma-S (1-10 microM), but not alpha,beta-methylene ATP (alpha,beta-MeATP; 100 microM) produced a slow outward current at a holding potential of 0 mV. When K+ was replaced in the pipette solution by an equimolar concentration of Cs+ (150 mM), the 2-methylthio ATP- (300 nM) induced outward current disappeared. The effect of 2-methylthio ATP (300 nM) did not depend on the presence of extracellular Mg2+ (1 mM). The outward current response to 2-methylthio ATP (300 nM) was larger in proliferating than in non-proliferating microglia. 3. ATP (1-1000 microM) evoked a fast inward current at a holding potential of -70 mV in nonproliferating microglia, while adenosine (100-1000 microM) was inactive. When the effects of ATP were compared at 0 and -70 mV, it became evident that ATP is much more potent in evoking the outward current. 4. The 2-methylthio ATP- (300 nM) induced outward current was blocked by suramin (300 microM), but not by 8-(p-sulphophenyl)-theophylline (100 microM), while the adenosine- (1 microM) induced outward current had the reverse sensitivity to these antagonists. 5. The 2-methylthio ATP- (300 nM) induced outward current was inhibited by inclusion of GDP-beta-S(200 microM) into the pipette solution or by preincubation of microglial cells with pertussis toxin(50 ng ml-1) for 12 h. The 2-methylthio ATP- (300 microM) induced inward current was not changed by intracellular GDP-beta-S (200 microM). The outward current response to adenosine (1 microM) was also abolished after pretreatment with pertussis toxin (50 ng ml-1).6. Rat microglia possess both ATP-sensitive P2y- and adenosine-sensitive P1-purinoceptors. The ATP evoked inward current is mediated by P2y-purinoceptors, while the ATP- and adenosine-evoked outward currents are mediated by P2y- and P1-purinoceptors, respectively. The transduction mechanisms of the outward, but not the inward current activation involve a pertussis toxin-sensitive G protein.

Th1-like cell responses to peripheral nerve myelin components over the course of experimental allergic neuritis in Lewis rats

Experimental allergic neuritis (EAN) is a T cell-mediated animal model of Guillain-Barré syndrome characterized by inflammation and demyelination of peripheral nerves. EAN can be induced by immunization of rats with bovine peripheral nerve myelin (BPM) or the myelin proteins P2 or P0, but the extent of T cell responses over the course of EAN is incompletely defined. We studied the T cell responses to these proteins and the glycolipid GM1 by enumerating T helper type 1 (Th1)-like cells secreting interferon-gamma (IFN-gamma) after short-term culture of mononuclear cells (MNC) in presence of antigen. Already 7 days post immunization (p.i.) with BPM and before onset of clinical EAN, lymph nodes contained elevated levels of P2 responsive T cells. At the height of EAN on day 14 p.i. and during recovery, T cell levels responding to BPM, P0 and GM1 were also elevated. The same temporal profiles and specificities were registered for antigen reactive spleen MNC. The results implicate that Th1-like cells with multiple specificities including the glycolipid GM1 occur at increased levels in lymphoid organs in EAN rats, and that IFN-gamma may be an important effector molecule in the induction of nerve damage.

Expression of adhesion molecules and HLA-DR by macrophages and dendritic cells in aphthoid lesions of Crohn's disease: an immunocytochemical study

The phenotypes and ultrastructure of macrophages and dendritic cells in aphthoid lesions of the colon were immunocytochemically observed in patients with Crohn's disease. Biopsy specimens were endoscopically obtained from both aphthoid and advanced lesions in Crohn's disease patients. Biopsy specimens obtained from patients with infectious colitis and from normal individuals served as controls. Aphthoid lesions contained densely aggregated CD68+ macrophages, which were surrounded by numerous ID-1+ dendritic cells. In the normal controls and infectious colitis patients, however, a few scattered CD68+ macrophages and ID-1+ dendritic cells were noted beneath the surface epithelium. CD3+ lymphocytes were significantly increased in both aphthoid and advanced lesions of Crohn's disease, but the CD4/CD8 ratio was similar in all groups studied. The double immunoperoxidase staining method revealed that both CD68+ macrophages and ID-1+ dendritic cells in the aphthoid lesions simultaneously expressed ICAM-1 and HLA-DR antigens. Electronmicroscopic observation revealed that CD68+ macrophages had numerous vesicles and lysosomal granules and few projections, and that ID-1+ dendritic cells had appreciable cytoplasmic protrusions with a few vacuoles. These findings suggested that the colonic mucosa in Crohn's disease contained two types of macrophage/dendritic cells in the same lineage that expressed intercellular adhesion molecules and class-II MHC antigens. It also appeared that the aphthoid lesions of Crohn's disease featured an increase in macrophages and dendritic cells consistent with immunological activation.

Augmented interferon-gamma, interleukin-4 and transforming growth factor-beta mRNA expression in blood mononuclear cells in myasthenia gravis

The abnormal T lymphocyte-dependent production of antibodies to the nicotinic acetylcholine receptor (AChR) in myasthenia gravis (MG) suggests a role for immunoregulatory cytokines. We examined the T helper type 1 (Th1) cell-associated interferon-gamma (IFN-gamma) that promotes cell-mediated immunity, the Th2 cell-related interleukin-4 (IL-4) that augments B cell immunity, and transforming growth factor-beta (TGF-beta) that downregulates immune responses but enhances isotype switching. Blood mononuclear cells (MNC) expressing cytokine mRNA were enumerated after in situ hybridization with labelled complementary DNA oligonucleotide probes for IFN-gamma, IL-4 and TGF-beta. MG patients had elevated numbers of cells expressing IFN-gamma and IL-4 compared to patients with non-inflammatory neurological diseases and healthy controls, implying that both Th1- and Th2-like cells are involved in MG. TGF-beta-positive cells were also elevated in MG. The levels of cytokine-positive MNC were similar in MG and in control patients with other inflammatory neurological diseases. There were no associations between numbers of cytokine-positive blood MNC and clinical variables of MG, but individual patients need to be studied over the course of MG to clarify a relation between the cytokines under study and clinical or laboratory variables of MG.

Characterization and possible function of adenosine 5'-triphosphate receptors in activated rat microglia

1. Purinoceptor agonist-induced currents in untreated (proliferating) and lipopolysaccharide (LPS; 100 ng ml-1)-treated (non-proliferating) rat microglial cells in culture were recorded by the whole-cell patch-clamp technique. These cells have two preferred resting membrane potentials, one at -35 mV and another one at -70 mV. 2. Most experiments were carried out in non-proliferating cells. ATP, ATP-gamma-S and alpha,beta-MeATP (1-1000 microM in all cases) evoked an inward current at a holding potential of -70 mV, followed, in some experiments, by an outward current. At -70 mV 2-methylthio ATP (1-1000 microM) evoked an inward current, whereas at -35 mV it produced an outward current only. 3. When K+ was replaced in the pipette solution by an equimolar concentration of Cs+ (150 mM), the main outward component of the ATP-gamma-S (10 microM) induced response disappeared. Instead, an inward current was obtained. Replacement of K+ by Cs+ did not affect the inward current evoked by 2-methylthio ATP (300 microM). 4-Aminopyridine (1-10 mM), however, almost abolished this current and unmasked a smaller outward current. 4. The rank order of agonist potency was 2-methylthio ATP > ATP > alpha,beta-MeATP. Adenosine and UTP were inactive. Suramin (300 microM) and reactive blue 2 (50 microM) antagonized the effect of 2-methylthio ATP (300 microM). 5. I-V relations were determined by delivering fast voltage ramps before and during the application of 2-methylthio ATP (300 microM). In the presence of extra- (1 mM) and intracellular (150 mM) Cs+, the 2-methylthio ATP-evoked current crossed the zero current level near 0 mV. When both Cs+ (1 mm) and 4-aminopyridine (1 mM) were present in the bath medium, the intersection of the 2-methylthio ATP current with the zero current level was near - 75 mV.6. 2-Methylthio ATP (1-1I000 MicroM) induced the same inward current both in proliferating and nonproliferating microglia. However, the depolarizing response to 2-methylthio ATP (300 MicroM) was larger and longer-lasting in the proliferating cells. When the free Ca2+ concentration in the pipettes was increased from the standard 0.01 to 1 MicroM, the amplitude and duration of this depolarization was increased in non-proliferating cells. 4-Aminopyridine (1 mM) enhanced the duration, but not the amplitude of responses.7. ATP and its structural analogues stimulate microglial purinoceptors of the P2Y-type. This leads to the opening of non-selective cationic channels and potassium channels. Depending on the resting membrane potential, depolarization or hyperpolarization prevails. Although the inward current produced by 2-methylthio ATP is of similar amplitude in proliferating and non-proliferating microglia, the resulting depolarization is smaller in the latter cell type because of the presence of voltage-sensitive, outwardly rectifying potassium channels.

Acetylcholine receptor-reactive T cells in myasthenia gravis: evidence for the involvement of different subpopulations of T helper cells

Patients with myasthenia gravis have a high prevalence of acetylcholine receptor-specific T lymphocytes in the peripheral blood. Our earlier study shows that these T lymphocytes are stimulated to secrete interferon (IFN)-gamma and interleukin (IL)-2 in response to the autoantigen. Such stimulated T cells may be subdivided into different subsets according to the pattern of cytokine production. In the present study we have investigated the subpopulations of cells by analyzing their IL-4, IFN-gamma and IL-2 secretion pattern. Autoantigen-stimulated IL-4 secretion was found in 55% of the patients, IFN-gamma secretion in 86% and IL-2 secretion in 72%. T lymphocytes from all patients who responded with increased IL-2 secretion also showed increased IFN-gamma secretion. Stimulated IL-4 secretion was detected both in the presence and absence of stimulated IFN-gamma secretion. Depletion of monocytes/macrophages from peripheral blood mononuclear cell preparation and treatment of the cells with a mouse anti-human HLA-DR antibody abolished the secretion of IFN-gamma and IL-4. There were positive correlations between the numbers of IFN-gamma- and IL-2-secreting T cells and the numbers of B cells secreting antibodies against the acetylcholine receptor. Our results show that acetylcholine receptor-stimulated T lymphocytes secrete IL-4, IFN-gamma and/or IL-2. This T cell response is major histocompatibility complex (MHC) class II-restricted and monocyte/macrophage-dependent. Our study indicates that both Th1/Th2 or Th0 subpopulations of the T lymphocytes are involved in the autoimmune response in myasthenia gravis.

Induction and down-regulation of PLK, a human serine/threonine kinase expressed in proliferating cells and tumors

We have identified the nucleotide sequence of the cDNA encoding the human counterpart of the mouse gene Plk (polo-like kinase). The sequence of the human gene, PLK, predicts a serine/threonine kinase of 603 aa. Expression of PLK mRNA appeared to be strongly correlated with the mitotic activity of cells. Resting peripheral lymphocytes did not express the gene at all. When primary T cells were activated by phytohemagglutinin, a high level of PLK transcripts resulted within 2-3 days. In some cases, addition of interleukin 2 to these cells increased the expression of PLK mRNA further. In contrast, primary cultures of human peripheral macrophages, which were not dividing under the culture conditions applied, showed very little or no PLK mRNA. Stimulation of these cells by bacterial lipopolysaccharide, an inducer of several cytokines in macrophages, totally abrogated the expression of PLK mRNA. In line with a function of PLK mRNA expression in mitotically active cells is our finding that six immortalized cell lines examined expressed the gene. In A-431 epidermoid carcinoma cells this expression was down-regulated by serum starvation and enhanced after serum was added again. Tumors of various origin (lung, colon, stomach, smooth muscle, and esophagus as well as non-Hodgkin lymphomas) expressed high levels of PLK transcripts in about 80% of the samples studied, whereas PLK mRNA was absent in surrounding tissue, except for colon. The only normal tissues where PLK mRNA expression was observed were colon and placenta, both known to be mitotically active. No PLK transcripts were found in normal adult lung, brain, heart, liver, kidney, skeletal muscle, and pancreas. In Northern blot experiments with RNA from lymphocytes which were treated with phytohemagglutinin and cycloheximide, PLK transcripts were not detectable, suggesting that PLK is not an early growth-response gene.

A monoclonal antibody (ER-HR3) against murine macrophages. II. Biochemical and functional aspects of the ER-HR3 antigen

We describe the purification and intracellular distribution of an antigen present on a subpopulation of murine macrophages and recognized by monoclonal antibody ER-HR3 against bone marrow-derived haemopoietic reticulum cells. Using the ER-HR3 antibody as an immobilizing ligand, two proteins were isolated as determined by SDS polyacrylamide gel electrophoresis. Under non-reducing conditions, there was a major band with an apparent molecular mass of 69 kDa and a minor band of 55 kDa. Under reducing conditions, the apparent molecular mass of each band was estimated as 76 kDa and 67 kDa, respectively. Intracellularly, these proteins occurred in close association with membranous structures, as demonstrated with gold-labelled protein A in an electron-microscopic study of the ER-HR3-positive cell line AP284. Some of the antigen was present in vesicles. To gain further insight into the possible function of the ER-HR3 antigen, its tissue distribution was investigated under distinct experimental conditions. In mice infected with Bacillus Calmette Gurèrin, ER-HR3-positive cells were observed in many, but not all, granulomata of the spleen, the lung and the liver. The ER-HR3 reactivity in these mice clearly differed from that of other antimacrophage monoclonal antibodies, such as F4/80, M5/114 and M1/70. Furthermore, phenylhydrazine-induced extramedullary erythropoiesis in the liver was accompanied by ER-HR3 expression on a subpopulation of macrophages. Finally, the addition of ER-HR3 to an antigen-specific T cell proliferation assay did not inhibit T cell proliferation.

Voltage-dependent potassium channels in activated rat microglia

1. Voltage-dependent currents of untreated (proliferating) and lipopolysaccharide (LPS)-treated rat microglial cells in culture were recorded using the whole-cell patch-clamp technique. 2. Membrane potentials showed prominent peaks at -35 mV and -70 mV. Membrane potentials of LPS-treated cells alternated between the two values. This may be due to a negative slope region of the I-V relation resulting in two zero current potentials. 3. From a holding potential of -70 mV, hyperpolarizing steps evoked an inwardly rectifying current both in proliferating and in LPS-treated cells, while depolarizing steps below -50 mV evoked an outwardly rectifying current only in LPS-treated microglia. The currents were K+ selective, as indicated by their reversal potential of approximately 0 mV in symmetric K+ concentrations (150 mM both intra- and extracellularly) and the reversal potential of the outward tail currents of approximately -90 mV at a normal extracellular K+ concentration (4.5 mM). 4. The activation of the outward current could be fitted by Hodgkin-Huxley-type n4 kinetics. The time constant of activation depended on voltage. 5. The inactivation of the inward and outward currents could be fitted by a single exponential. The time constant of the inward current inactivation was dependent on voltage, whereas the time constant of the outward current inactivation was virtually independent of voltage, except near the threshold of activation. Recovery of the outward from inactivation was slow and could be fitted by two exponentials. Responses to depolarizing steps were stable at 0.125 Hz, but greatly decreased from the first to the second pulse at 1 Hz. 6. The inactivation of the inward, but not of the outward, current disappeared in a low Na(+)-containing medium (5 mM). The inward current was selectively inhibited by extracellular Cs+ and Ba2+. The outward current was selectively inhibited by Cd2+, 4-aminopyridine and charybdotoxin. Replacement of intracellular K+ by an equimolar concentration of Cs+, and the extracellular application of tetraethylammonium and quinine inhibited both currents. 7. An increase of extracellular Ca2+ from 2 to 20 mM resulted in outwardly rectifying K+ channels activating at more positive potentials. Omission of Ca2+ from the extracellular medium had the opposite effect. When the intracellular free Ca2+ was increased from 0.01 to 1 microM, the outward current amplitudes were depressed. The Ca2+ ionophore A23187 had a similar effect. 8. LPS-treated microglial cells possess inwardly and outwardly rectifying K+ channels. The physiological and pharmacological characteristics of these two channel populations are markedly different.(ABSTRACT TRUNCATED AT 400 WORDS)

HIV antigen-reactive T cells detected by antigen-induced interferon gamma secretion

The T cell repertoire to human immunodeficiency virus (HIV) was studied in HIV-infected patients of different clinical stages by the detection and enumeration of cells that secreted interferon gamma (IFN-gamma) in short-term cultures of blood mononuclear cells after stimulation in vitro with the HIV recombinant antigens pB1, p121, p24-15, gp160bac, and the HIV V3 loop peptide. T cell reactivities to cytomegalovirus (CMV) and Mycobacterium tuberculosis-purified protein derivative (PPD) were examined in parallel. Among 29 patients with HIV infection, 48% had blood cells recognizing one or more of the five HIV antigens. The mean numbers of HIV antigen-reactive T cells varied between 1/approximately 6000 blood cells for pB1 and 1/approximately 20,000 cells for p24-15. None of the five HIV antigens studied was identified as an immunodominant T cell epitope in HIV infection. T cells from 20% of the patients responded to all five HIV antigens in parallel, but the antigen preferentially recognized varied from patient to patient. Those with more advanced disease had a tendency to lower numbers of HIV antigen-reactive T cells. Most HIV-infected patients had both CMV- and PPD-reactive T cells, but numbers were significantly lower in more advanced disease. It should be possible to adopt the present method to evaluate fine specificities of the T cell repertoire to other antigens and to study the involvement of other cytokines besides IFN-gamma, for example, the Th2 cell-related cytokine interleukin 4.

In vitro cytokine production by HLA-B8,DR3 positive subjects

It is well known that healthy subjects carrying the HLA-B8,DR3 haplotype may show an impairment of immune system, the T cells being the most affected. To gain insight into the mechanism(s) of the impairment displayed by these subjects, efforts have been centered on the study of in vitro cytokine production because of the pivotal role played by these mediators in the activation and control of several immune functions. The available results indicate that the ability to several immune functions. The available results indicate that the ability to produce interleukin-1 (IL-1), IL-2 and the soluble form of its receptor (sIL-2R) is impaired in HLA-B8,DR3 positive healthy subjects. To better characterize the cytokine production capacity of HLA-B8,DR3 positive subjects, we have investigated the pattern of in vitro production of IL-2, sIL-2R, IL-4. IL-6 and gamma-interferon (gamma-IFN) by mononuclear cells from HLA-B8, DR3 positive subjects after phytohaemoagglutinin stimulation. A significant decrease of IL-2, sIL-2R and gamma-IFN production by HLA-B8,DR3 positive subjects was observed. No significant difference was instead found between the HLA-B8,DR3 positive subjects and the negative ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response that may observed in HLA-B8,DR3 positive subjects, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.

The lipophosphoglycan of Leishmania and macrophage protein kinase C

Lipophosphoglycan (LPG), the major cellsurface glycoconjugate of Leishmania promastigotes, is on essential virulence determinant. One feature of LPG resides in its strong inhibitory effect on the activity of purified protein kinase C (PKC). In this article, Albert Descoteaux and Salvatore Turco briefly review the evidence that LPG effectively inhibits PKC activity in the macrophage, and discuss the implication of such inhibition on Leishmania intramacrophoge survival.

Leukemic cell lysis by activated human macrophages: significance of membrane-associated tumor necrosis factor

In this study, we analyzed the mechanism(s) of leukemic cell lysis by human macrophages. Peripheral blood monocyte-derived macrophages were activated with recombinant interferon-gamma and lipopolysaccharide and their lytic activity against two leukemic cell lines (K562 and HL-60 cells) was assessed by an 111In releasing assay. Activated macrophages lysed these leukemic cells, and the lytic activity against leukemic cells was almost completely inhibited by anti-tumor necrosis factor (TNF) antibody. The macrophage-lysate prepared from activated macrophages also exhibited significant lytic activity against leukemic cells; this lytic activity was inhibited by anti-TNF antibody. The leukemic cells that we used for the cytotoxicity assays were resistant to recombinant TNF. The culture supernatant of activated macrophages did not show any lytic activity. These findings suggest that cell-associated TNF plays a role in macrophage-mediated cytotoxicity against leukemic cells.

The role of cytokines in experimental listeriosis

Listeria monocytogenes is a Gram-positive, intracytoplasmatically replicating pathogen that elicits host reactions which are very similar in man and rodents. Using murine listeriosis as a highly reproducible and convenient experimental model for studying the immune response to infections with facultative intracellular bacteria, Mackaness developed the concept of T cell-mediated macrophage activation as the pivotal mechanism in host defense against this type of infectious agents. Continued research in listeriosis itself, however, provided paradoxical findings that challenged the original dogma. In particular, the finding that T cell-mediated inflammatory events, like DTH and granuloma formation, can be dissociated from protective effector mechanisms has provided a new impetus and experimental access to characterizing the molecular mediators responsible for these diverging phenomena. This review first summarizes the cellular basis for the dichotomy of immunological phenomena outlined above and will then relate recent findings on cytokine expression in infected tissues to these dual categories of the host response to infection. The authors will focus on data obtained from in vivo experiments and draw on evidence from in vitro systems only when appropriate in vivo verification is still lacking. The data presented will cover the developments made in the field of cytokine research since our previous review in 1981 (Rev. Infect. Dis. 3: 1221-1250). Detectable numbers of listeria-specific T cells become apparent on day 4 to 5 of a primary infection. Whereas the localized and sustained release of TNF and IFN-gamma mediated by CD4+ cells seems to be the focusing event triggering mononuclear cell accumulation, the coincidental eradication of bacteria critically depends on CD8+ and/or CD4-CD8-Thy1+ cells. Their effector functions, however, remain obscure, since cytokines cannot be identified that will substitute for their presence. None of the cytokines studied thus far has been demonstrated to effectively cure an established infection. In addition, the increased production of cytokines characteristic of an anamnestic response (IL-2, IL-3, IL-4, IFN-gamma and TNF) can be dramatically reduced by depleting CD4+ T cells without any effect on the animal's ability to eradicate high lethal doses of bacteria and Listeria-specific CD8+ T cells can mediate protection even in the presence of neutralizing antibodies to IFN-gamma. In conclusion, the murine model of Listeria infection provides an interesting experimental approach for the development of immunotherapeutic strategies aimed at reducing T cell-mediated immunopathology without interfering with innate resistance and T cell-mediated cure and prevention of disease.

Mechanisms of immune activation of human immunodeficiency virus in monocytes/macrophages

Monocytes/macrophages (M/M) are the major host of human immunodeficiency virus (HIV) in solid tissues. However, blood monocytes are nonpermissive for HIV infection, indicating that M/M activation or differentiation is necessary for HIV replication. Since M/M are activated during immune responses, we investigated the effect of T-cell activation on HIV expression in M/M derived from peripheral blood of HIV-infected individuals. Previously, we reported that coculture of monocytes from HIV-infected donors with T cells and mitogens resulted in M/M differentiation and HIV expression. Production of HIV by M/M from infected donors required direct contact between monocytes and T cells (for the first 24 h), and the response to alloantigens, but not mitogens, was restricted to HLA-DR. In this study, we found that HIV was more readily recovered from M/M of asymptomatic HIV seropositive donors (69%) than from M/M of symptomatic donors (57%). Viral antigens (e.g., inactivated herpes simplex virus) could initiate the immune response and HIV expression. The ability of noninfected T cells to activate HIV expression in M/M and observations that treatments of M/M with antibodies to deplete T cells did not reduce HIV expression suggested that the monocytes were endogenously infected. To define the aspects of immune activation specifically involved in initiating HIV expression in M/M, interactions of M/M and T cells and participation of cytokines were investigated. The T cell which activated M/M was CD4+ CD8-. Fixed allogeneic cells are known to induce T-cell activation but were not able to serve as antigen for M/M differentiation, suggesting that M/M may need to function as antigen-presenting cells to receive the signal to differentiate and express HIV. Blocking of M/M-T-cell interaction with antibodies directed against LFA-1 or interleukin-1 prevented HIV expression. However, inhibition of later stages of T-cell activation, such as blocking of interleukin-2 receptors, did not diminish HIV expression in M/M. Consistent with the requirement for cell-cell contact between M/M and T cells, a variety of cytokines were unable to initiate HIV replication in M/M. The ability of T cells to induce cellular differentiation and HIV replication in M/M in vitro suggests that initiation of an immune response to an antigen, such as an opportunistic pathogen, could be a mechanism by which HIV disseminates to tissues in vivo.

Augmentation of macrophage phagocytic activity by cell-free extracts of selected lactic acid-producing bacteria

Oral and intraperitoneal administration of lactic acid-producing bacteria can significantly augment the immune response in murine models; however, the immunopotentiating effects in these studies differ significantly. Murine macrophagelike cell line J774 was cultured in the presence of cell-free extracts of Lactobacillus acidophilus and Bifidobacterium longum, and the effect on macrophage function was evaluated by measurement of synthesis of selected enzymes and their ability to take up either acrylamide particles or live Salmonella typhimurium. Lysozyme activity of J774 cells was significantly decreased by cell-free extracts of B. longum, but not of L. acidophilus, whereas extracts of both strains induced morphological changes and significantly enhanced phagocytosis of inert particles or viable Salmonella. Whole cell extracts of lactic acid-producing bacteria are therefore capable of altering macrophage function in a strain-dependent manner.

Somatolactogens, somatomedins, and immunity

The neuroendocrine and immune systems participate as active partners in host homeostatic and defense mechanisms. This partnership involves a complex intercommunication system employing an array of shared ligands and receptors. Hormones of the somatolactogen family have marked influences on immune events in vivo, including the maintenance of lymphoid tissue cellularity, the promotion of DNA synthesis in these tissues, and the stimulation of a number of immune effector mechanisms. Both growth hormone and prolactin function to promote erythropoiesis and DNA synthesis in bone marrow precursors. Our results have shown that the somatolactogens and a member of the somatomedin family, IGF-I, are particularly effective in modulating the effector functions in phagocytic cells, including the production of reactive oxygen intermediates and tumor necrosis factor-alpha and the oxygen-dependent killing of bacteria. Evidence indicating a role of IGF-I in modulating immune functions is more recent but nonetheless compelling. Accumulated data suggest that somatolactogenic hormones, as well as one member of the somatomedins, are produced by cells of the immune system and can regulate local immune events. Although the molecular mechanisms by which the somatolactogens and somatomedins exert their effects on immune tissues are only now being explored, the pleiotropic nature of these effects suggests that these hormones participate at endocrine, paracrine, and perhaps autocrine sites of action.

Autoreactive T and B cell responses to myelin antigens after diagnostic sural nerve biopsy

To study whether nervous tissue trauma provokes myelin antigen autoreactive T and B cell responses in humans we examined consecutive blood samples from 7 patients with polyneuropathy undergoing diagnostic sural nerve biopsy and 8 control patients undergoing other types of minor surgery. The antigen-specific T cells were assessed by enumerating cells secreting interferon-gamma (IFN-gamma) in response to the myelin components P0, P2, myelin basic protein (MBP) and myelin associated glycoprotein (MAG), and to 4 selected MBP peptides. B cell mediated immunity was assessed by counting numbers of cells secreting antibodies directed against the myelin proteins. On day 7 after biopsy, there were 3-10-fold increased numbers of T and B cells reactive with P0, P2, MBP and MAG in blood of polyneuropathy patients compared to controls, while levels of cells recognizing purified protein derivate or responding to phytohemagglutinin (PHA) did not differ significantly. Comparison of prebiopsy levels on day 0 with post-biopsy levels on day 7 in the polyneuropathy patients revealed a significant increase in T cells recognizing P0, P2 and MAG, and in B cells secreting IgG antibodies against P0 and P2. On day 14 after nerve biopsy these differences were no longer seen. We suggest that in patients with polyneuropathy, sural nerve biopsy with the ensuing wallerian degeneration and myelin breakdown causes transiently increased levels of circulating myelin autoreactive T and B cells. It remains to be determined if this has a physiological role in nerve trauma responses and/or affects the clinicopathological course of the peripheral neuropathy.