Role Of Interleukin-2 Research Articles

693. Regression of Established Subcutaneous B16 Melanoma Tumors after Intratumoral Delivery of a IL-15 Expressing Plasmid Followed by In Vivo Electroporation

Melanoma is a major cancer due to metastasis; however, its initial cutaneous presentation makes it amenable to therapy. In vivo electroporation (E) has been used recently to efficaciously deliver conventional drugs and therapeutic genes to tumors, including melanomas. This study reports on the intratumoral (IT) delivery of DNA plasmids expressing interleukin-15 (IL-15), i.e. pIL-15, to established subcutaneous B16 melanoma tumors in C57BL6 mice. The IL-15 expression plasmid used was optimized for expression and was 80 fold more efficient than standard pcDNA3 based plasmids. IL-15 has been shown to have a pivotal role in the function of memory CD8 T cells and natural killer cells, both of which are critical for tumor immunosurveillance in vivo. In this study, female C57BL6 mice were injected, subcutaneously in the flank, with 1 million B16F10 melanoma cells. Approximately 7 days later, when tumor volumes were approximately 40 cu mm (day 0), mice (n=8/group) were randomized into different groups: untreated (V-P-E-) or treated with 50micrograms of pIL-15 (P) or backbone plasmid (V) with or without E (E+-/E-) (E conditions = 6 pulses 100microsecs 1500 V/cm). Subsequent treatments of the groups were made on days 4 and 7 and tumor volumes and survival among the groups were measured after the treatment regimen. Results at day 35-post treatment showed 0, 25 and 71% complete tumor regression in the V+-E+-, P+-E- and P+-E+- groups respectively. Likewise, at day 35 mice survival for the V+-E+-, P+-E-, P+-E+- and V-P-E- groups were 25, 50, 100 and 0% respectively. In addition, tumor growth, as measured by tumor volume, in mice without complete tumor regression was considerably less in the P+-E+- group (177 cu mm) when compared to the P+-E- (518 cu mm) and V+-E+-(1175 cu mm) groups. In addition, IL-15 expression in tumor lysates was considerably higher (7.5 fold) in the P+-E+- treated animals (21.6 pg/mg tumor) compared to the P+-E- group (2.9pg/mg tumor) demonstrating the efficacy of E+- to significantly enhance the expression of pIL-15 and potentially mediate an enhanced therapeutic effect. These results demonstrate the ability of an IL-15 expressing DNA plasmid to mediate an increase in complete regression of established subcutaneous B16 melanoma tumors when delivered intratumorally along with E. This is the first description of the ability of an IL-15 expressing DNA plasmid to alone mediate complete regression in this tumor type. These results are relevant since B16F10 tumors are characteristically difficult to treat and cure and underscores the potential clinical use of IL-15 for the treatment of malignant tumors when delivered with in vivo E. Mechanistic studies on the effects of the treatments reported here are being pursued and are centering on the previously established role of IL-15 in CD8+- T cell and natural killer cell activity.

Epirubicin and Gemcitabine as First-Line Treatment in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma represents a rare disease, for which chemotherapy actually remains unsatisfactory. From August 1998 to November 2001, 28 chemo-radio-immunonaive patients were consecutively enrolled in the trial: 22/6 males/females; median age 63 years (range, 45-79); median ECOG PS 1 (range, 0-2). They were treated with epirubicin (100 mg/m2 iv on day 1) plus gemcitabine (1000 mg/m2 iv on days 1 and 8) every 4 weeks for 6 cycles. Patients who responded to chemotherapy (n = 6) were subsequently treated with interleukin-2 (4,500,000 IU) subcutaneously every other day, until progression. A total of 124 epirubicin-gemcitabine cycles were administered (median, 6/patient; range, 2-6). Twenty-six patients were evaluated for toxicity. According to WHO criteria, we observed grade III-IV hematological and gastrointestinal toxicity respectively in 3 patients (11%) and 1 patient (3%). No red cell transfusions were required and no toxic deaths occurred. Two patients (8%) could not be evaluated for response (no therapy performed). According to WHO criteria, the final responses were: partial in 4 patients (14%), stable disease in 19 patients (69%), and progression in 3 patients (10%). In 26 patients, the median survival was 55 weeks (range, 7-222) and median time to progression 30 weeks (range, 4-156). At the time of this writing, no patient is alive. The 1-year survival was 32%, 2-year survival 11%, and 4% at 3 and 4 years. All patients were at stage III, and time to progression was 58 weeks and survival 63.5 weeks, without any toxicity. This multi-center phase II clinical trial showed that epirubicin plus gemcitabine, as a first-line treatment in malignant pleural mesothelioma, has promising activity with a good tolerability profile and symptom palliation. The role of interleukin-2 in maintenance therapy for malignant pleural mesothelioma is encouraging and requires further study.

Exogenous IL-7 induces Fas-mediated human neuronal apoptosis: potential effects during human immunodeficiency virus type 1 infection

The use of exogenous cytokines is part of translational immune-antiretroviral approaches to induce immune reconstitution and possibly eliminate the persistence of human immunodeficiency virus type 1 (HIV-1) in virally suppressed infected individuals on highly active antiretroviral therapy (HAART). Recently, our laboratories demonstrated that interleukin-7 (IL-7) has significant efficiency in stimulating HIV-1 replication from proviral latency in CD4+ T lymphocytes of infected patients. The authors now investigated the possible role of IL-7 in HIV-1-associated dementia (HAD). The authors demonstrated that the IL-7 receptor is expressed on both human neurons (i.e., differentiated NT2 cells) and human astrocytes, with relatively higher mRNA levels in neurons. The translational protein levels of IL-7 receptor alpha were not proportional to those of the mRNA levels in these central nervous system (CNS)-based cell types. Exogenous IL-7 was observed to only slightly down-regulate IL-7 receptor alpha expression on both neurons and astrocytes, as assayed by Western blotting. Instead of promoting survival, surprisingly, exogenous IL-7 induced neuronal apoptosis, as detected by TUNEL assays. Furthermore, IL-7 augmented neuronal apoptosis induced by HIV-1 gp120. Human apoptosis genomic microarray analyses of IL-7-treated human neurons showed up-regulated expression of proapoptotic genes: protein kinases, caspase-10, FAST kinase, tumor necrosis factor (TNF) receptor, and BCL2-antagonist of cell death. These data suggest that IL-7 leads to neuronal apoptosis by a molecular mechanism(s) that occurs via Fas-mediated activation-induced cell death. These studies may therefore not only be key in evaluating the potential use of IL-7 in vivo as a therapeutic modality, but also suggest that IL-7, which is increased endogenously in HIV-1-infected individuals late in disease, may be involved in the neuronal apoptosis demonstrated during HAD.

Hapten-induced contact hypersensitivity is enhanced in Tyk2-deficient mice

Previous studies have shown that Tyk2, a member of the Janus family of protein tyrosine kinases, which are activated by a variety of cytokines, plays a crucial role in interleukin (IL)-12-mediated T-cell functions such as IFN-gamma production. On the other hand, hapten-induced contact hypersensitivity (CHS) is mediated by IFN-gamma producing CD8+ T cells and regulated by CD4+ T cells. This study hypothesized that the CHS response might be reduced in Tyk2-deficient mice because of a lack of IFN-gamma production from CD4+ and CD8+ T cells. The CHS reaction was evoked in wild-type and Tyk2-deficient mice and the ears of the mice were examined to measure for several cytokines. Ear swelling during CHS was significantly enhanced in Tyk2-deficient mice compared with the controls. IL-12 and IFN-gamma levels at the reaction sites in Tyk2-deficient mice were significantly lower than in the controls, whereas IL-2 and IL-4 levels were elevated. Furthermore, STAT3- and STAT4-phosphorylation in the draining lymph node cells of Tyk2-deficient mice decreased. These results suggest that the lack of Tyk2-mediated signal transduction enhances a compensative pathway during CHS.

Induced tolerance to cardiac allografts with multiple intravenous injection of donor spleen cells

To study the methods and mechanisms of immune tolerance in cardiac transplantation. Male DA rat hearts were transplanted to male Lewis rats using Ono's model and randomly divided into five groups: untreated, intravenous injection of 1 x 10(8) DA splenocytes to Lewis rat, intraperitoneal injection of cyclophosphamide (100 mg/kg) to Lewis rat, intravenous injection of 1 x 10(8) DA splenocytes combined with intraperitoneal injection of cyclophosphamide (100 mg/kg) to Lewis rat, multiple injection of DA rat splenocytes with intraperitoneal injection of cyclophosphamide, 11 days later heart transplantation was performed. Mean survival time (MST), histological changes, mixed lymphocyte reaction (MLR), the role of interleukin-2 (IL-2) to MLR and the role of tolerant rat splenocytes to MLR were measured after operation. The survival time of heart allografts in the group of multiple injection of DA rat splenocytes with intraperitoneal injection of cyclophosphamide [MST: (85.3 +/- 7.5) d, t = 0, P < 0.01] was significantly longer than in the groups of untreated [MST: (7.3 +/- 1.0) d], intravenous injection of 1 x 10(8) DA splenocytes to Lewis rat [MST: (7.9 +/- 0.9) d], intraperitoneal injection of cyclophosphamide (100 mg/kg) to Lewis rat [MST: (8.1 +/- 1.2) d], intravenous injection of 1 x 10(8) DA splenocytes combined with intraperitoneal injection of cyclophosphamide (100 mg/kg) to Lewis rat [MST: (25.8 +/- 3.5) d]. Only a few inflammatory cells infiltrated in cardiac allografts in the group of multiple injection of DA rat splenocytes with intraperitoneal injection of cyclophosphamide. MLR in the group of multiple injection of DA rat splenocytes with intraperitoneal injection of cyclophosphamide were significantly decreased compared with those of normal control (t = 0, P < 0.01). IL-2 could partly reversed the hyporesponsiveness of MLR in tolerant rats, the tolerance could be transferred in vitro. Multiple injection of donor splenocytes combined with intraperitoneal injection of cyclophosphamide to recipients could induce immune tolerance to cardiac allografts.

Growth and apoptosis of human natural killer cell neoplasms: role of interleukin-2/15 signaling

Interleukin (IL)-15 plays an important role in the survival of human natural killer (NK) cells. We investigated IL-2/15 signaling in NK cell neoplasms from five patients and in five cell lines (NK-92, KHYG-1, SNK-6, HANK1 and MOTN-1) compared to mature peripheral NK cells from 10 healthy subjects. Apoptosis of NK cell lines was prevented by addition of IL-15 in vitro. Blocking IL-2/15Rβ on IL-2-stimulated NK-92 cells resulted in reduced expression of Bcl-X L and phosphorylated Stat5, which paralleled early apoptosis without altering Bcl-2 expression. These data add IL-2/15Rβ to the list of factors important for the survival of NK cell neoplasms.

Mature dendritic cells can enhance CD8+cell noncytotoxic anti-HIV responses: the role of IL-15

AbstractThe CD8+cell noncytotoxic anti-HIV response (CNAR) is associated with a long-term healthy clinical state in HIV-infected individuals. Over time CNAR is reduced concomitant with progression to disease. In studies to evaluate whether the interaction between CD8+cells and dendritic cells (DCs) could increase CNAR, CD8+cells from individuals who showed a decrease in this antiviral activity were cocultured with monocyte-derived dendritic cells matured with CD40 ligand. After coculture with these mature DCs, the CD8+cells showed an increase in CNAR greater than that observed with CD8+cells costimulated with CD3/CD28 antibodies. This antiviral response appeared to be mediated primarily by production of interleukin-15 (IL-15) by the mature DCs. Purified IL-15 also enhanced CNAR, whereas IL-12 showed no substantial effect. These studies provide another potential approach by which the immune system in HIV infection could be restored by cytokine therapy, particularly IL-15 administration. (Blood. 2004;103:2699-2704)

Adenosine inhibits activation-induced T cell expression of CD2 and CD28 co-stimulatory molecules: role of interleukin-2 and cyclic AMP signaling pathways.

Adenosine is an immunosuppressive molecule that is associated with the microenvironment of solid tumors. Mouse T cells activated with anti-CD3 antibody in the presence of adenosine with or without coformycin (to prevent adenosine breakdown by adenosine deaminase) exhibited decreased tyrosine phosphorylation of some intracellular proteins and were inhibited in their ability to proliferate and synthesize interleukin (IL)-2. In addition, adenosine interfered with activation-induced expression of the co-stimulatory molecules CD2 and CD28. Activation-induced CD2 and CD28 expression was also diminished when T cells were activated in the presence of anti-IL-2 and anti-CD25 antibodies to neutralize IL-2 bioactivity. Collectively, these data suggest that CD2 and CD28 up-regulation following T cell activation is IL-2-dependent; and that adenosine inhibits activation-induced T cell expression of CD2 and CD28 by interfering with IL-2-dependent signaling. The inhibitory effect of adenosine on activation-induced CD2 and CD28 expression could not be attributed to cyclic AMP (cAMP) accumulation resulting from the stimulation of adenylyl cyclase-coupled adenosine receptors, even though cAMP at concentrations much higher than those generated following adenosine stimulation was inhibitory for both CD2 and CD28 expression. We conclude that adenosine interferes with IL-2-dependent T cell expression of co-stimulatory molecules via a mechanism that does not involve the accumulation of intracellular cAMP.

Role of interleukin-2 in the functional myocardial impairment induced by anoxia and reoxygenation

To investigate the effect of interleukin-2 (IL-2) on myocardial impairment during ischemia/reperfusion or anoxia/reoxygenation. Chemical anoxia was introduced in the isolated rat ventricular myocytes by Krebs-Henseleit (K-H) solution containing 10(-3) mol/L sodium dithionite. The video-tracking system and spectrofluorometric method were employed to verify the cell contraction and calcium homeostasis of the single myocyte. Radioimmunoassay was used to analyze the IL-2 levels in myocardium. The levels of IL-2 in myocardium subjected to ischemia/reperfusion were elevated [(14.34+/-5.99 compared with 22.25+/-3.68)ng/g, P<0.01]. During anoxia, cell contraction and the amplitude of electrically induced calcium transient were depressed and the parameters did not return to the pre-anoxia level during reoxygenation. IL-2 at 200 U/L administered during anoxia aggravated the effect of reoxygenation on cell contraction and calcium transient. After perfusion with IL-2, the malondialdehyde content of myocardial mitochondria was elevated. Coexistence of IL-2 during anoxia aggravates the effect of reoxygenation on the cell contraction and calcium homeostasis in the isolated rat ventricular myocytes, in which the mitochondrial lipid peroxidation induced by IL-2 is involved.

Regulation of the Dephosphorylation of Stat6: PARTICIPATION OF TYR-713 IN THE INTERLEUKIN-4 RECEPTOR α, THE TYROSINE PHOSPHATASE SHP-1, AND THE PROTEASOME

Signal transducer and activator of transcription 6 (Stat6) plays an important role in interleukin (IL)-4-induced responses. To analyze the regulation of Stat6 phosphorylation, cells were cultured in the continuous presence of IL-4 or after a pulse and washout. In the continual presence of IL-4, Stat6 remained phosphorylated for an extended period. After IL-4 removal and inhibition of the Janus family kinase, tyrosine-phosphorylated Stat6 decayed at a rate dependent upon the length of IL-4 stimulation. The decay of tyrosine-phosphorylated Stat6 was similar in the presence or absence of either cycloheximide or actinomycin D. In the absence of functional Src homology-containing phosphatase-1 (SHP-1), the early loss of tyrosine-phosphorylated Stat6 was substantially reduced. Furthermore, the rate of loss of tyrosine-phosphorylated Stat6 in cells expressing a mutation of the human IL-4 receptor alpha in the immunoreceptor tyrosine-based inhibitory motif sequence (Y5F) was dramatically decreased compared with wild-type cells. The early rate of decay was similar in the presence or absence of MG132, an inhibitor of the proteasome, but the later rate of decay was decreased 5-fold. These results suggest that the loss of tyrosine phosphorylation of Stat6 is regulated by the action of SHP-1 and the proteasome but is not dependent on new protein synthesis.

Role of interleukin-15 and interleukin-18 in the secretion of sIL-6R and sgp130 by human neutrophils.

BACKGROUND: Available data indicate that neutrophils (PMN) produce a wide range of cytokines with the potential to modulate immune response. Recent investigation have shown that interleukin (IL)-15 and IL-18 potentiated several functions of normal neutrophils. It has been reported that IL-18-induced cytokine production may be significantly enhanced by coincident addition of IL-15. AIMS: In the present study we compared the effect of recombinant human (rh)IL-15 and rhIL-18 as well as effect of a rhIL-15 and rhIL-18 combination on the induction secretion of sIL-6Ralpha and sgp130 by human neutrophils. METHODS: PMN were isolated from heparinized whole blood of healthy persons. The PMN were cultured for 18 h at 37 degrees C in a humidified incubator with 5% CO(2). rhIL-15 and/or rhIL-18 and lipopolysaccharide were tested to PMN stimulation. The culture supernatants of PMN were removed and examined for the presence of sIL-6R and sgp130 by human enzyme-linked immunosorbent assay kits. Cytoplasmic protein fractions of PMN were analysed for the presence of sIL-6R and sgp130 by western blotting using monoclonal antibodies capable of detecting these proteins. Cells were lysed and cytoplasmic proteins were electrophoresed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The resolved proteins were transferred onto nitrocellulose and incubated with the primary monoclonal antibodies anti-sIL-6R and anti-sgp130. The membranes were incubated at room temperature with alkaline phosphatase anti-mouse immunoglobulin G. Immunoreactive protein bans were visualized by an AP Conjugate Substrate Kit. RESULTS AND CONCLUSIONS: The results of our investigation revealed that IL-15 alone, similarly to IL-18, has no significant ability for the regulation of both soluble IL-6 receptors, sIL-6R and sgp130, released by human neutrophils. It is interesting to note that the secretion of sgp130 was changed after PMN stimulation with rhIL-15 in the presence of rhIL-18. The combination of rhIL-15 and rhIL-18 was shown to induce PMN to secretion relatively higher amounts of sgp130 compared with the stimulation of PMN with rhIL-15 alone and rhIL-18 alone. The results obtained suggest that IL-15 and IL-18, belonging to the inflammatory cytokines, through the regulation of sgp130 secretion must be also considered as anti-inflammatory mediators that may influence the balance reactions mediated by the IL-6 cytokine family.

Responses of bovine WC1(+) gammadelta T cells to protein and nonprotein antigens of Mycobacterium bovis.

WC1(+) gammadelta T cells of Mycobacterium bovis-infected cattle are highly responsive to M. bovis sonic extract (MBSE). In mycobacterial infections of other species, gammadelta T cells have been shown to respond to protein and nonprotein antigens, but the bovine WC1(+) gammadelta T-cell antigenic targets within MBSE require further definition in terms of the dominance of protein versus nonprotein components. The present study sought to characterize the WC1(+) gammadelta T-cell antigenic targets, together with the role of interleukin-2 (IL-2), in the context of M. bovis infection. This was achieved by testing crude and defined antigens to assess protein versus nonprotein recognition by WC1(+) gammadelta T cells in comparison with CD4(+) alphabeta T cells. Both cell types proliferated strongly in response to MBSE, with CD4(+) T cells being the major producers of gamma interferon (IFN-gamma). However, enzymatic digestion of the protein in MBSE removed its ability to stimulate CD4(+) T-cell responses, whereas some WC1(+) gammadelta T-cell proliferation remained. The most antigenic protein inducing proliferation and IFN-gamma secretion in WC1(+) gammadelta T-cell cultures was found to be ESAT-6, which is a potential novel diagnostic reagent and vaccine candidate. In addition, WC1(+) gammadelta T-cell proliferation was observed in response to stimulation with prenyl pyrophosphate antigens (isopentenyl pyrophosphate and monomethyl phosphate). High levels of cellular activation (CD25 expression) resulted from MBSE stimulation of WC1(+) gammadelta T cells from infected animals. A similar degree of activation was induced by IL-2 alone, but for WC1(+) gammadelta T-cell division IL-2 was found to act only as a costimulatory signal, enhancing antigen-driven responses. Overall, the data indicate that protein antigens are important stimulators of WC1(+) gammadelta T-cell proliferation and IFN-gamma secretion in M. bovis infection, with nonprotein antigens inducing significant proliferation. These findings have important implications for diagnostic and vaccine development.

Role for IL-7 in HIV

A recent report by researchers at the Gladstone Institute of Virology and Immunology in San Francisco shows that during HIV infection, interleukin 7 (IL-7) is responsible for T-cell production in response to T-cell depletion but that it also increases HIV-1 replication. In a study of 187 HIV-1 seropositive adults, levels of IL-7 were found to correlate negatively with both total and naive CD4?+ counts. None of the other cytokines or hormones studied showed a similar correlation. Using immunohistochemistry, the researchers found that IL-7 is produced by dendritic-like cells within peripheral lymphoid tissues, and that IL-7 production by these cells is greatly increased in lymphocyte-depleted tissues. The scientists also found that HIV load was higher when IL-7 levels were elevated, regardless of the disease stage or whether the patients were receiving antiviral therapy. The authors believe that IL-7 could be useful in enhancing lymphopoiesis in other settings in which the immune system has been destroyed, such as chemotherapy or bone marrow transplantation. Nat. Med. (2001) 7, 73–79. HM

Interleukin-2 inhibits eosinophil migration but is counteracted by IL-5 priming.

Conflicting data on the role of interleukin-2 in the recruitment of eosinophil granulocytes (EOS) to sites of inflammation have been presented. The objective of the present study was to investigate the effect of recombinant human IL-2 and anti-IL-2 on the migration of purified blood EOS. Neutralizing antibodies to IL-2 were added to a cytokine mixture with significant eosinophil chemotactic activity (ECA), and afterwards the ECA was tested on EOS from both normal and allergic donors. EOS migration was measured by a modification of the Boyden technique, using a 48-well microchemotaxis chamber. Recombinant human IL-2 was either added to the lower compartment of the chemotaxis chamber, or to the EOS for a pre-incubation period of 20 min, before migration assays towards the chemotaxins were performed. Anti-IL-2 caused a significant increase of EOS migration towards the cytokine mixture. Pre-incubation of the EOS with rhIL-2 inhibited the chemotaxis towards RANTES, PAF, IL-8 and eotaxin, and EOS migration towards IL-2 was lower than that towards buffer. These effects were more pronounced on EOS from normal than from allergic donors. Priming of the EOS with IL-5 prevented the inhibitory effect of IL-2. We hypothesize that IL-2 acts as an autocrine regulator of EOS migration, and that this inhibitory effect may be downregulated in allergy, allowing an increased migration of EOS towards chemotactic factors.

Innate response cytokines in inflammatory synovitis: a role for interleukin-15.

Innate response cytokines in inflammatory synovitis: a role for interleukin-15.

Serum cytokine levels in autoimmune and non-autoimmune hyperthyroid states.

Although the role of interleukin-2 (IL-2) and interferon gamma (gammaIFN) is still poorly understood in hyperthyroid diseases, it is reasonable to assume that these cytokines may be present at higher levels in Graves' disease (GD) than in other primarily non-autoimmune thyroid diseases. In order to look for an easy method to distinguish GD from primarily non-autoimmune causes of hyperthyroidism, we compared 13 healthy individuals with 21 treated and untreated hyperthyroid GD patients and with 19 patients with hyperthyroidism due to other etiologies: 7 cases of multinodular goiter, 5 cases of excessive hormone replacement and 7 cases of amiodarone-associated hyperthyroidism. All patients presented low TSH levels and a dubious clinical thyroid state. We found a good correlation between TSH and serum IL-2 levels (r = 0.56; P<0.01). Serum IL-2 (P<0.01) and gammaIFN (P<0.01) levels were lower in the hyperthyroid group of patients than in control subjects, suggesting a depressed TH1 pattern in the T-cell subset of hyperthyroid patients. GD had normal IL-2 levels, while patients with other forms of thyrotoxicosis presented decreased IL-2 levels (P<0.05). There was no difference between treated and untreated GD patients. We suggest that the direct measurement of serum IL-2 level may help to confirm hyperthyroidism caused by GD.

Role of interleukin-7 in the relation between Schistosoma mansoni and its definitive vertebrate host

Human schistosomiasis is a chronic inflammatory disease caused by blood fluke worms belonging to the genus Schistosoma. Health metrics indicate that the disease is related to an elevated number of years lost-to-disability and years lost-to-life. Schistosomiasis is an intravascular disease that is related to a Th1 and Th2 immune response polarization, and the degree of polarization affects the outcome of the disease. The purinergic system is composed of adenosine and nucleotides acting as key messenger molecules. Moreover, nucleotide-transforming enzymes and cell-surface purinergic receptors are obligatory partners of this purinergic signaling. In mammalian cells, purinergic signaling modulates innate immune responses and inflammation among other functions; conversely purinergic signaling may also be modulated by inflammatory mediators. Moreover, schistosomes also express some enzymes of the purinergic system, and it is possible that worms modulate host purinergic signaling. Current data obtained in murine models of schistosomiasis support the notion that the host purinergic system is altered by the disease. The dysfunction of adenosine receptors, metabotropic P2Y and ionotropic P2X7 receptors, and NTPDases likely contributes to disease morbidity.

The role of interleukin-2 in regulating the sensitivity of natural killer cells for Fas-mediated apoptosis.

The Fas/Fas-ligand (FasL) system seems to play a key role in regulating immunoresponses. Highly purified CD56+CD3- natural killer (NK) cells were found to be resistant to the apoptosis-inducing Fas mAb CH11 in the absence or in the presence of interleukin-2 (IL-2) for up to 3 days. However, NK cells activated with IL-2 for 3 days became apoptotic following combined treatment with CH11 and actinomycin D, suggesting the presence of an intact apoptotic machinery. In contrast, NK cells cultivated in IL-2 for 6 days became sensitive to CH11-induced apoptosis without addition of actinomycin D. At this time, a pronounced up-regulation of the Fas protein on the NK cell membrane was detected. By using reverse transcription/polymerase chain reaction it was found that the anti-apoptotic gene FLIP was strongly expressed in NK cells for up to 6 days of IL-2 stimulation. After day 6, a time-dependent decrease in the expression of FLIP was observed concomitantly with increased sensitivity for Fas-mediated apoptosis. The amount of apoptotic and necrotic NK cells in the presence of IL-2 increased in a time-dependent manner, reaching 40% at day 6 of culture. The amount of apoptotic and necrotic NK cells was reduced in the presence of Fas-Fc protein. In addition, IL-2 stimulated the NK cells to release soluble FasL in a time-dependent manner, whereas membrane FasL did not seem to increase in a similar manner. These results indicate that Fas/FasL interactions are involved in the down-regulation of IL-2-activated human NK cells.

Downregulation of JAK3 Protein Levels in T Lymphocytes by Prostaglandin E2 and Other Cyclic Adenosine Monophosphate-Elevating Agents: Impact on Interleukin-2 Receptor Signaling Pathway

The Janus kinase, JAK3 plays an important role in interleukin-2 (IL-2)-dependent signal transduction and proliferation of T lymphocytes. Our findings show that prostaglandin E2 (PGE2) can inhibit upregulation of JAK3 protein in naive T cells and can downregulate its expression in primed cells. Reduction in JAK3 was selective because expression of other tyrosine kinases (JAK1, p56(lck), and p59(fyn)) and signal transducer and activator of transcription (STAT)5, which are linked to IL-2 receptor (IL-2R) signaling pathway, were not affected. Inhibition of JAK3 may be controlled by intracellular cyclic adenosine monophosphate (cAMP) levels, as forskolin, a direct activator of adenylate cyclase and dibutyryl cAMP (dbcAMP), a membrane permeable analogue of cAMP suppressed JAK3 expression. Moreover, 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of cAMP phosphodiesterase, potentiated PGE2-induced suppression of JAK3. In naive T cells, but not primed T cells, PGE2 and other cAMP elevating agents also caused a modest reduction in surface expression of the common gamma chain (gammac) that associates with JAK3. The absence of JAK3, but not IL-2R in T cells correlated with impaired IL-2-dependent signal transduction and proliferation. The alteration in IL-2 signaling included decreased tyrosine phosphorylation and DNA binding activity of STAT5 and poor induction of the c-Myc and c-Jun pathways. In contrast, IL-2-dependent induction of Bcl-2 was unaffected. These findings suggest that suppression of JAK3 levels may represent one mechanism by which PGE2 and other cAMP elevating agents can inhibit T-cell proliferation.

Downregulation of JAK3 Protein Levels in T Lymphocytes by Prostaglandin E2 and Other Cyclic Adenosine Monophosphate-Elevating Agents: Impact on Interleukin-2 Receptor Signaling Pathway

AbstractThe Janus kinase, JAK3 plays an important role in interleukin-2 (IL-2)–dependent signal transduction and proliferation of T lymphocytes. Our findings show that prostaglandin E2(PGE2) can inhibit upregulation of JAK3 protein in naive T cells and can downregulate its expression in primed cells. Reduction in JAK3 was selective because expression of other tyrosine kinases (JAK1, p56lck, and p59fyn) and signal transducer and activator of transcription (STAT)5, which are linked to IL-2 receptor (IL-2R) signaling pathway, were not affected. Inhibition of JAK3 may be controlled by intracellular cyclic adenosine monophosphate (cAMP) levels, as forskolin, a direct activator of adenylate cyclase and dibutyryl cAMP (dbcAMP), a membrane permeable analogue of cAMP suppressed JAK3 expression. Moreover, 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of cAMP phosphodiesterase, potentiated PGE2-induced suppression of JAK3. In naive T cells, but not primed T cells, PGE2 and other cAMP elevating agents also caused a modest reduction in surface expression of the common gamma chain (γc) that associates with JAK3. The absence of JAK3, but not IL-2R in T cells correlated with impaired IL-2–dependent signal transduction and proliferation. The alteration in IL-2 signaling included decreased tyrosine phosphorylation and DNA binding activity of STAT5 and poor induction of the c-Myc and c-Jun pathways. In contrast, IL-2–dependent induction of Bcl-2 was unaffected. These findings suggest that suppression of JAK3 levels may represent one mechanism by which PGE2 and other cAMP elevating agents can inhibit T-cell proliferation.