Phosphorylation of human interleukin-2 (IL-2)

Human interleukin-2 (IL-2) is a lymphokine which is capable of activating lymphocytes and supporting the long-term in vitro growth of activated T cell clones. Recombinant human IL-2, expressed in either E. coli or cos cells, was shown to be phosphorylated by protein kinase C. Phosphorylated IL-2 synthesized in E. coli was analyzed by SDS-PAGE, reverse phase HPLC, and tryptic peptide mapping. The phosphorylated tryptic peptide was identified as the N-terminal fragment containing a single phosphorylation site at the serine residue at position 7. There was no difference in biological activity between non-phosphorylated and phosphorylated IL-2, as determined by a T cell growth assay. Although the physiological role of phosphorylation of IL-2 is unclear, IL-2 can be labeled with [-^32p] ATP and protein kinase C to a high specific radioactivity, and the synthesis of biologically active ^32p-labeled IL-2 may be useful for receptor-binding studies of the cells containing low level of phosphoprotein phosphotases.Abbreviations IL-2 Interleukin-2 - rIL-2 recombinant IL-2 - SDS-PAGE Sodium Dodecylsulfate Polyacrylamide Gel Electrophoresis, Tris tris (hydroxymethyl)-amino methane - RP-HPLC Reverse Phase High Pressure Liquid Chromatography - PTH Phenylthiohydantoin - IFN- Leukocyte Interferon - IFN- Fibroblast Interferon - IFN- Immune Interferon By acceptance of this article, the publisher or recipient acknowledges the right of the U.S. Government to retain a nonexclusive, royalty-free license in and to any copyright covering the articleResearch being carried out at the Frederick Cancer Research Facility, Frederick, Maryland     

A cell-free Salmonella typhimurium extract modulates interleukin-2 (IL-2) receptor expression but not IL-2-stimulated responses of murine splenic lymphocytes

Abstract In a previous study, we observed that a cell-free Salmonella typhimurium extract induced suppression of mitogen-induced T-cell proliferation and this suppression involved non-responsiveness of T-cells to interleukin-2 (IL-2). In this study, we found that a cell-free S. typhimurium extract modulated IL-2 receptor (IL-2R) expression on phytohemagglutinin (PHA)-stimulated murine spleen cells and this was a mechanism of T-cell non-responsiveness to IL-2, but did not affect IL-2 binding to IL-2R and the consequent responses. Western blotting using anti-phosphotyrosine antibodies showed that IL-2R-mediated tyrosine phosphorylation of protein substrates in PHA-activated murine splenic T-cells, which express a high-affinity IL-2R (α- and β-chains), was not affected by treatment with the S. typhimurium cell-free extract. Furthermore, PHA-activated spleen T-cells responded to recombinant IL-2 and this was not inhibited by the extract. Surprisingly, IL-2R expression was augmented by treatment with the extract, although this was independent of IL-2 production. These results suggest that the suppression of T-cell proliferation induced by the Salmonella cell-free extract was associated with augmentation of IL-2R expression, rather than down-regulation of the IL-2 response. This may be a mechanism responsible for the Salmonella extract-evoked suppression of mitogen-induced T-cell proliferation.     

Identification of structural differences between different forms of interleukin-2 (IL-2) using anti-(human recombinant) IL-2 monoclonal antibodies.

We have generated a panel of murine monoclonal antibodies (mAbs) directed against recombinant human interleukin-2 (rh IL-2). All mAbs have similar affinities (Kaff approximately equal to 10(-8) M) and are of the IgG1 isotype. Specificity of the mAbs has been established using an ELISA method and immunoprecipitation of native human interleukin-2 (nh IL-2) present in supernatants from PHA-stimulated human mononuclear cells (PBMNC). Four of the nine mAbs inhibit the rh IL-2-dependent proliferation of a murine cytotoxic T-lymphocyte line (CTLL-2). The estimated ID50, in the presence of 0.75 IU rh IL-2/ml, ranges from 2.0 micrograms/ml to 30 micrograms/ml final concentrations of the antibodies. Using different forms of IL-2 we found that the mAbs give different patterns of inhibition of the IL-2-dependent proliferation. One mAb (AMCIB 27) is able to discriminate between rh and nh IL-2. Findings with another mAb (AMCIB 24) indicate that possible functional differences between human IL-2 and recombinant murine (rm) IL-2 are caused by differences in the active sites. The results of this investigation show that it is possible to obtain mAbs, after immunization with rh IL-2, that differ in their ability to inhibit the biological action of different forms of IL-2.     

Therapeutic efficacy of human recombinant interleukin-2 (TGP-3) alone or in combination with cyclophosphamide and immunocompetent cells in allogeneic,semi-syngeneic,and syngeneic murine tumors

Summary The potential for a recombinant human interleukin-2 (rIL-2, TGP-3) alone, in combination with cyclophosphamide, and in combination with cyclophosphamide and normal immunocompetent cells to manifest biological activity in vivo was tested using allogeneic, semi-syngeneic, and syngeneic tumor-host systems in mice. The biological activity of rIL-2 was evaluated by the inhibition of the growth of tumors and the inhibition of metastases in short-term assays and, in long-term assays, the prolongation of the survival time of mice bearing subcutaneously (s.c.) or intradermally transplanted tumors. rIL-2 was injected s. c. daily continuously for up to 40 days or intermittently two to four times into mice bearing established tumors. In the short-term assays, the dose and schedule dependence of activity of rIL-2 alone was significantly manifested against sarcoma 180 in ICR mice (allogeneic) by the regression of the tumor, and was confirmed against Meth-A fibrosarcoma in BALB/c mice (syngeneic) by retarding the growth of the tumor. When assessed using these tumors, it was found that the antitumor activity of rIL-2 was scheduledependent: the growth of tumors was more significantly suppressed when rIL-2 was injected every day for 10 days, starting on the 7th day after tumor transplantation, than when rIL-2 was injected five times every other day or twice every 5th day, even if the total amounts of rIL-2 injected were same. The continuous injection for 10 days was considered to be a standard regimen and the daily effective doses of rIL-2 were 5, 10, and 25 µg/mouse. Using the standard regimen and the effective doses, the activity of rIL-2 alone was also observed against two other syngeneic tumors: Colon carcinoma 26 in BALB/c mice, by retarding the growth of the tumor, and Lewis lung carcinoma in C57BL/6 mice by reducing the formation of lung metastases. When assessed using M5076 reticulum cell sarcoma, in a long-term assay, the activity of rIL-2 alone was not manifested in C57BL/6 mice (syngeneic) even when rIL-2 was injected for a long period (20 days) but it was observed in BDF1 (semi-syngeneic) mice. On the other hand, it was found that rIL-2 was effective in combination with cyclophosphamide in prolonging the survival time of C57BL/6 mice bearing the tumor. After cyclophosphamide (2.0 mg) had been administered orally to mice on the 6th day after tumor transplantation, the tumor regressed temporarily but regrew; however, when rIL-2 at a dose of 10 µg was also injected daily for a long period (40 days), the regrowth was retarded and the survival time of the mice was significantly prolonged. Moreover, when normal immunocompetent cells were transferred at the tumor sites, the regrowth of the tumors was retarded more significantly even at a daily dose of 1 µg or 3 µg rIL-2, and mice were observed to be cured by daily doses over 3 µg. The results obtained in the syngeneic tumor-host systems indicate that the continuous injection of rIL-2 is necessary and important for its activity to be manifest in vivo, and that, when combined with cytotoxic drugs and/or with immunocompetent cells, the potential efficacy of rIL-2 is valuable in cancer therapy.     

SOCS2 can enhance interleukin-2 (IL-2) and IL-3 signaling by accelerating SOCS3 degradation

Cytokine responses can be regulated by a family of proteins termed suppressors of cytokine signaling (SOCS) which can inhibit the JAK/STAT pathway in a classical negative-feedback manner. While the SOCS are thought to target signaling intermediates for degradation, relatively little is known about how their turnover is regulated. Unlike other SOCS family members, we find that SOCS2 can enhance interleukin-2 (IL-2)- and IL-3-induced STAT phosphorylation following and potentiate proliferation in response to cytokine stimulation. As a clear mechanism for these effects, we demonstrate that expression of SOCS2 results in marked proteasome-dependent reduction of SOCS3 and SOCS1 protein expression. Furthermore, we provide evidence that this degradation is dependent on the presence of an intact SOCS box and that the loss of SOCS3 is enhanced by coexpression of elongin B/C. This suggests that SOCS2 can bind to SOCS3 and elongin B/C to form an E3 ligase complex resulting in the degradation of SOCS3. Therefore, SOCS2 can enhance cytokine responses by accelerating proteasome-dependent turnover of SOCS3, suggesting a mechanism for the gigantism observed in SOCS2 transgenic mice.     

Relationship between circulating interleukin-10 (IL-10) with interleukin-6 (IL-6) type cytokines (IL-6, interleukin-11 (IL-11), oncostatin M (OSM)) and soluble interleukin-6 (IL-6) receptor (sIL-6R) in patients with multiple myeloma

We investigated the serum concentration of the interleukin-10 (IL-10), along with cytokines of interleukin-6 (IL-6) family (IL-6, IL-11 and oncostatin M - OSM), as well as soluble receptor for IL-6 (sIL-6R), in 121 patients with multiple myeloma (MM) and 28 healthy subjects. We studied the interactions between IL-10 and other cytokines, and the receptor. The correlation between IL-10 and some clinical and laboratory parameters associated with the disease activity were also analysed. The IL-10 was detectable in all patients with multiple myeloma and in all controls. The IL-10 concentration was significantly increased in myeloma patients compared with healthy persons (mean - 7.09 and 2.1 pg/ml, respectively) (p = 0.008). The level of IL-10 correlated positively with the advanced stage of disease estimated according to the Salmon and Durie classification (I versus III stage - p = 0.03). Higher values of IL-10 were found in patients with the light chain disease, hypercalcaemia, and correlated with the elevated concentrations of C-reactive protein (CRP). IL-6 was detected in 117 of the 121 patients and in all controls. The concentration of IL-6 was statistically increased in MM patients compared with control group (mean - 16.06 and 4.49 pg/ml, respectively) (p = 0.01). We found a positive correlation between IL-10 and IL-6 serum levels in MM patients. The relationship, expressed as Spearman's rank sum coefficient (rho = 0.249, p = 0.006) was significant. IL-11 was detected in 26 of the 121 MM patients and in 3 of the 28 healthy subjects at the mean concentration of 1.2 and 0.6 pg/ml respectively (p > 0.05). OSM was at detectable levels in 51 of the 121 patients and in only 4 of the 28 controls (mean - 3.84 and 0.1 pg/ml, p = 0. 002). The correlation between IL-10 and IL-11 levels in MM patients was not significant, but there was a strong statistical correlation between IL-10 and OSM concentrations (rho= 0.327, p = 0.0002). The serum concentration of sIL-6R was measurable in all patients and all controls (mean - 66.00 and 39.57 ng/ml respectively), but the difference between these groups was not significant. We found significant, positive correlation between the levels of IL-10 and sIL-6R (rho= 0.233, p = 0.01). In conclusion, we state that the serum concentrations of IL-10, IL-6, OSM and sIL-6R in MM patients may be a useful markers for the evaluation of the disease activity.     

A murine cell line (2E10.4.13) produces five hemopoietic stimulators, and interleukin-2 and interleukin-3

An interleukin-2 (IL-2)-independent murine lymphocyte clone (2E10.4.13) with the Thy1+Lyt1+2-T200+ phenotype was separated from the original IL-2-dependent natural killer (NK) cell line (PEC-1). Erythroid burst-promoting activity (BPA), erythropoietin (Ep), granulocyte/macrophage, megakaryocyte and eosinophil colony-stimulating factors (GM-, MK- and Eo-CSF), IL-2 and Interleukin-3 (IL-3) were produced when these cells were stimulated with phorbol myristate acetate (PMA). When the conditioned medium was run through ion-exchange high-performance liquid chromatography, BPA, Ep, GM-CSF, MK-CSF and Eo-CSF were eluted in the same region as IL-3. In contrast, MK-CSF, much of the GM-CSF and half of the Eo-CSF were eluted in a distinct region where no IL-3 was detected. Chemical analyses of the hemopoietic factors derived from a single T inducer clone indicated that all the hemopoietic activities were associated with IL-3 activity. Some CSF activities (GM-, MK- and Eo-CSF) also could be mediated by the distinct molecules from IL-3, evidence that heterogeneous molecules are responsible for CSF activity.     

Combination of vasostatin and cyclophosphamide in the therapy of murine melanoma tumors

Growth of tumors is strongly dependent upon supply of nutrients and oxygen by de novo formed blood vessels. Inhibiting angiogenesis suppresses growth of primary tumors as well and affects development of metastases. We demonstrate that recombinant MBP/vasostatin fusion protein inhibits proliferation of endothelial cells in vitro. The therapeutic usefulness of such intratumorally delivered recombinant protein was then assessed by investigating its ability to inhibit growth of experimental murine melanomas. In the model of B16-F10 melanoma the MBP/vasostatin construct significantly delayed tumor growth and prolonged survival of treated mice. A combination therapy involving MBP/vasostatin construct and cyclophosphamide was even more effective and led to further inhibition of the tumor growth and extended survival. We show that such combination might be useful in the clinical setting, especially to treat tumors which have already formed microvessel networks.     

Prostaglandin E2 (PGE2) differentially regulates the production of IL-2 and IL-3 by murine immune T-cells.

Eicosanoids are important mediators of inflammation, and have been shown to have potent, and usually suppressive immunoregulatory activities. In the paper, we have examined the role of prostaglandin (PGE2) production in the regulation of two cytokines, IL-2 and IL-3, which both play a key role in contact sensitivity and delayed type hypersensitivity reactions. In agreement with previous studies, we demonstrate that prostaglandins down-regulate IL-2 production in the system. Unexpectedly, however, IL-3 levels are enhanced in the presence of the prostaglandin PGE2 and conversely, are inhibited by treatment with aspirin, a potent inhibitor of prostaglandin metabolism. The implications of this result in terms of the immunoregulatory role of PGs will be discussed.     

Expression of interleukin-2 receptor (IL-2R) in feline peripheral blood lymphocytes

A monoclonal anti-interleukin-2 receptor (IL-2R) antibody has been identified as a putative antibody against the human IL-2R. In the present study, anti-Tac antibody CD-25 was used to determine cell expressing IL-2 receptor in feline peripheral blood lymphocytes by means of direct immunofluorescence tests and complement-mediated lymphocytotoxicity tests. With complement-mediated lymphocytotoxicity, approximately 18% of feline peripheral blood lymphocytes expressed the receptors. By the direct immunofluorescence test, we found approximately 22% of IL-2R positive cells in lymphocytes of feline peripheral-blood.     

Soluble interleukin-2 receptor (S IL-2R) in renal and pancreatic transplantation.

The monitoring of plasma soluble interleukin-2 receptor (S IL-2R) concentrations has been proposed in organ transplantation, especially to detect early manifestations of rejection. In organ transplantation, immune activation occurs in various circumstances such as rejections and infections. We performed S IL-2R determination 3 times a week in the sera of 106 patients undergoing kidney and/or pancreas transplantation. In kidney transplantation, S IL-2R was increased before the transplant. It also increased under prophylactic and especially under curative anti-rejection OKT3 or ATG therapy. In 90% cases, S IL-2R increased 2 to 4 days before creatininemia rise. In the other 10% cases, no correlation could be found with any clinical status modification. S IL-2R concentrations never increased in isolated acute tubular necrosis or in cyclosporine A (CsA) nephrotoxicity. In pancreas transplantation, the correlation between S IL-2R concentrations and possible pancreas rejection, was very poor. During cytomegalovirus (CMV) infection, only 50% patients with clinical CMV manifestations had high concentrations of S IL-2R. During Dihydroxy Propoxy Methyl Guanine (DPHG = Ganciclovir) treatment, S IL-2R still increased at the beginning, then it decreased progressively when therapy was efficient on CMV infection. The monitoring of S IL-2R concentrations may be useful in the weeks following organ transplantation provided that results are interpreted in the context of clinical and other laboratory findings, particularly with the renal function status and creatininemia.     

Measurement and partial characterization of an interleukin-2 inhibitor (IL-2-IN) in human urine

We observed a human urine-derived protein complex (IL-2-IN) which competitively inhibits interleukin-2 (IL-2) dependent murine lymphocyte proliferation. Measurements of urinary IL-2-IN have been used to stratify the immune response of patients to bacteria in the bladder. Partial characterization of IL-2-IN indicates that it is a heat-stable, 75 kDa complex comprised of interleukin-2 bound to another protein(s). Although the IL-2-IN complex is stable in physiologic buffers, the complex can be disrupted using acidic or low-ionic strength buffers, thereby liberating IL-2. IL-2-IN activity is susceptible to bacterial and endogenous urinary proteolysis. The IL-2 bound in the IL-2-IN complex cannot be detected using a double monoclonal antibody radioimmunoassay for IL-2. Unlike other IL-2 binding proteins, the IL-2 binding protein of the IL-2-IN complex is not a soluble interleukin-2 receptor. A modification of the bioassay for interleukin-2 activity is the method of choice for the detection and quantification of urinary IL-2-IN.     

IL-12 treatment of endogenously arising murine brain tumors

A number of recent studies have indicated that T cells can be stimulated to attack transplanted brain tumors in rodent models. As IL-12 has been shown to activate cytotoxic T cell responses, we tested the idea that it might stimulate a T cell response against endogenous brain tumors that arise in SV40 large T Ag transgenic mice (SV11). SV11 mice develop tumors of the choroid plexus, a specialization of the ependymal lining of the brain ventricles. They are a particularly relevant model of human disease, because they are immunocompetent but immunologically tolerant of the tumors. SV11 mice were treated with recombinant murine IL-12 for 10 days. Tumors grew more slowly than in control treated mice, and in some cases were reduced in size, as assessed by magnetic resonance imaging before and after treatment. At the end of treatment, tumors, but not brain parenchyma, exhibited extensive infiltration of activated CD8(+) and CD4(+) T cells. Tumors also showed a reduction in vascular density. Mice treated with IL-12 lived significantly longer than control mice. Tumors that progressed were nearly devoid of T cells, indicating that the T cell response was not sustained. In addition, some mice that had a substantial tumor burden at the beginning of treatment displayed evidence of immunosuppression, which might be related to TGF-ss2 detected in tumors. We conclude that IL-12 treatment can initiate an anti-tumor response even against endogenously arising brain tumors, but factors that will allow a sustained and more effective anti-tumor response need to be determined.     

Phorbol esters can persistently replace interleukin-2 (IL-2) for the growth of a human IL-2-dependent T-cell line

A selected clone from an IL-2-dependent human T-cell line was persistently propagated in the presence of phorbol esters with the ability to activate protein kinase C (PKC), such as 12-O-tetradecanoylphorbol-13-acetate (TPA) or phorbol-12,13-dibutylate (PDBu). Thus, a TPA(PDBu)-dependent T-cell line, designated TPA-Mat, was established from IL-2-dependent T cells. The TPA-dependency of TPA-Mat was not lost during cultivation for more than a year in the presence of TPA, and TPA-Mat cells still showed IL-2-dependent growth. However, the TPA (PDBu)-dependent growth of TPA-Mat did not seem to be mediated by an autocrine mechanism of IL-2 or by any other growth factor production, because these factors were not detected in TPA-Mat cell supernatants. Therefore, the phorbol esters substituted for IL-2 and may be directly involved in transduction of growth signals in TPA-Mat cells. Although activity of PKC was down-regulated, messenger ribonucleic acid (mRNA) of the PKC beta-gene was detected in TPA-Mat cells cultured with PDBu. Furthermore, the growth of TPA-Mat cells was stimulated not only by phorbol esters but also by nonphorbol ester tumor promoters with the ability to activate PKC. These observations suggest that the sustained activation of PKC by the phorbol esters could induce continuous growth of the IL-2-dependent TPA-Mat cells.     

Effects of hyperlipaemic serum on interleukin-2 (IL-2) production, IL-2 receptor expression, and T cell proliferation induced by IL-2 in cynomolgus monkeys

The effect of hyperlipaemic serum on mitogen-induced T lymphocyte proliferation was investigated with cynomolgus monkeys. The mitogen-induced blastogenesis was remarkably inhibited when either hyperlipaemic or normal monkey lymphocytes were incubated with hyperlipaemic sera. Hyperlipaemic serum also inhibited ConA-induced interleukin 2 (IL-2) production as well as IL-2 receptor (IL-2R) expression of normal monkey lymphocytes. On the other hand, it showed slight inhibition of T-cell proliferation induced by adding recombinant human IL-2 to IL-2R-positive normal monkey lymphocytes. These results indicate that hyperlipaemic serum inhibited an early stage of T-cell autocrine activation pathway including IL-2 production and IL-2R expression.     

The combination of the interleukin-1alpha (IL-1alpha-889) genotype and the interleukin-10 (IL-10 ATA) haplotype is associated with increased interleukin-10 (IL-10) plasma levels in healthy individuals

Family studies have demonstrated striking differences between individuals in their ability to produce IL-10 following lipopolysaccharide (LPS) stimulation of whole blood cultures in vitro, suggesting that differences in IL-10 production involve a considerable hereditary component. The first aim of this study was to analyse the possible effect of IL-10 genotypes and haplotypes on IL-10 plasma levels in a healthy Finnish population. As previous reports have demonstrated that endogenously produced IL-1 induces LPS-stimulated IL-10 production and that IL-10 inhibits synthesis of IL-1 in human monocytes, it is apparent that these two cytokines form an autoregulatory feedback loop. Secondly, we were interested whether any relationship could be found between IL-10 and IL-1beta in vivo. To examine this, the influence of IL-1alpha -889, IL-1beta -511 and IL-1Ra VNTR genotypes and IL-10 genotypes/haplotypes (ACC, GCC and ATA) on IL-10 plasma levels, and a putative correlation between IL-10 and IL-1alpha plasma levels were analysed. Four hundred adult blood samples were obtained from the Finnish Red Cross Blood Transfusion Centre, Tampere. The IL-10, IL-1alpha, IL-1beta and IL-1Ra gene polymorphisms were analysed using PCR. IL-1beta and IL-10 plasma levels were measured using an ELISA method. Our results indicated that increased IL-10 plasma levels were associated with the ATA haplotype (p = 0.03) and, surprisingly, with the IL-1alpha allele 2 carrier status (p = 0.02) in healthy individuals. This IL-1alpha 2+/ATA+ combination was found in 93 subjects out of 400 analysed (23%) and was associated with significantly high IL-10 plasma levels (p = 0.002). When individuals were classified into three groups, with no detectable IL-10 plasma levels (n = 145), with moderate levels (n = 152) and with high levels (n = 100) of IL-10, the IL-1alpha2+/ATA+ combination was more likely present among those with high levels than among those with undetectable levels of IL-10 (OR = 3.3, 95% CI 1.8 - 6.0, p < 0.001) or those with moderate levels of IL-10 (OR = 2.0, 95% CI 1.2 - 3.6, p = 0.012). Besides the observed association between IL-1alpha genotype and IL-10 levels, a moderate correlation was found between IL-10 and IL-1beta levels (r = 0.6, p = 0.01) among IL-10 producers (n = 252). The present findings suggest that the genotype combination of IL-1alpha 2+/ATA+ has a regulatory effect on basal IL-10 levels and that among individuals with measurable IL-10 plasma levels, IL-1beta and IL-10 basal levels correlate. Until now, data on the feedback loop between IL-1 and IL-10 cytokines have been based on studies in vitro, but now our results suggest that this relationship may also exist in vivo.     

Plasma levels of interleukin-12 (IL-12), interleukin-18 (IL-18) and transforming growth factor beta (TGF-beta) in Plasmodium falciparum malaria

The interaction between pro- and anti-inflammatory cytokines such as interleukin 12 (IL-12), interleukin 18 (IL-18) and transforming growth factor beta (TGF-beta) may play an important role in malaria pathogenesis and outcome. IL-18 cooperates with IL-12 in the IFN-gamma production by T, B, and NK cells, and synergizes with IL-12 for IFN-gamma production by Th1 cells. Recently it has been demonstrated that these cytokines modulate the immunoresponse in Plasmodium falciparum malaria. The aim of this study was to measure the plasma levels of IL-12, IL-18 and TGF-beta in 105 African children with various degrees of malaria, and correlate the production of these cytokines with the severity of the disease. IL-12, IL-18 and TGF-beta levels were determined using enzyme-linked immunosorbent assay. The severity of malaria was established by parasitemia, clinical symptoms and haematological parameters. The levels of IL-12, IL-18 and TGF-beta were found to be significantly elevated (15.6 + / - 12.3, 22.7 + / - 13.8 pg/ml and 25.14 + / - 13.22 pg/ml respectively) in all of the children. IL-12 and IL-18 levels were significantly lower (13.2 + / - 5.53 and 21.5 + / - 10 pg/ml pg/ml) in children with severe disease, whereas the level of TGF-beta was higher (28.09 + / - 12.39 pg/ml). In contrast, IL-12 and IL-18 levels were found to be higher (17.32 + / - 7.8 pg/ml and 25.7 + / - 7.6 pg/ml) in patients with mild disease, whereas the level of TGF-beta was lower (20.92 + / - 12.76 pg/ml) compared to the severe malaria group. The correlation between IL-12 and IL-18 demonstrated a progressive relationship up to a value of IL-12 < 25 pg/ml, while IL-18 remained stable at higher levels of IL-12. An inverse correlation was found between IL-12 and TGF-beta up to a value of IL-12 < 30, after which the level of TGF-beta remained stable. This finding suggests that fine mechanisms regulate the interaction between IL-12, IL-18 and TGF-beta in the immune response to Plasmodium falciparum.     

Expression of murine interleukin-2 cDNA in E. coli and biological activities of recombinant murine interleukin-2

Murine interleukin-2 (MIL-2) cDNA was inserted into an expression vector carrying an Escherichia coli tryptophan promoter and was expressed in E. coli. Recombinant MIL-2 produced by E. coli supported the growth of murine CTLL-2 cells, but not that of human T-cell blasts. Recombinant MIL-2 strongly inhibited the binding of recombinant human IL-2 (HIL-2) to murine responder cells, but only very weakly inhibited the binding to human responder cells. Moreover, recombinant MIL-2 induced secondary alloantigen specific cytotoxic T lymphocytes (2 degrees CTL) from memory CTL and activated natural killer (NK) cells in murine systems in the same manner as recombinant HIL-2. The results suggest that the species hierarchy (that MIL-2 derived from native cell culture does not act on human T-cells) is due to the protein moiety, not the sugar moiety, and is to be ascribed to the difference in binding affinity of MIL-2 and HIL-2 to murine and human responder cells respectively, and that recombinant MIL-2 shares identical biological and immunological activities with recombinant HIL-2. Thus, MIL-2 might be a convenient tool for extensive studies of the pharmacological and physiological activities of IL-2 in murine models.     

Effects of interleukin-2 (IL-2) on human plasma lipid,lipoprotein, and C-reactive protein

Six patients with confirmed malignant disease received four consecutive weekly cycles of human recombinant interleukin-2 (IL-2) 4 days/week, continuous iv. infusion, 3 × 10⁶ U/m²/day. Plasma cholesterol decreased a mean of 7% within 24 hours after IL-2 infusion and decreased by 33% within 4 days. Plasma cholesterol was significantly lower than baseline concentration by day 21 (–21%), and day 25 (–41%) was significantly lower than day 21. Decreased plasma cholesterol was the result of decreased HDL and LDL cholesterol concentrations. Plasma triglyceride demonstrated a mean increase of 46% after 4 days of therapy and remained greater than baseline concentrations at all time points analyzed. Apolipoprotein AI and AII decreased concomitantly with HDL-cholesterol concentrations, whereas apolipoprotein B after an initial mean decrease of 17% during the first cycle was not significantly different from baseline during the fourth cycle. Apolipoprotein E and Lp(a) were not significantly affected by IL-2 treatment. Plasma C-reactive protein (CRP) increased by 79% within 24 hours of therapy, increased by 254% on day 4, then decreased to baseline concentrations by day 21 after 3 days off of IL-2. Day 25 CRP was elevated compared to both baseline and day 21 concentrations. IL-2 induced plasma lipoprotein changes may be due in part to the induction of interferon gamma.