Interactions between interferon gamma, tumour necrosis factor alpha, and interleukin-1 in modulating progesterone and oestradiol production by human luteinized granulosa cells in culture.

We have reported that the cytokines, interleukin-1 (IL-1), tumour necrosis factor alpha (TNF alpha), and interferon (IFN) alpha, beta, and gamma modulate the steroidogenic function of human luteinized granulosa cells in culture. In the present study we examined the interactions between these cytokines in modulating progesterone and oestradiol production by these cells. Neither IL-1 nor TNF alpha had significant effects on human chorionic gonadotrophin (HCG)-stimulated progesterone production, whereas IFN gamma (1-10 ng/ml) significantly reduced HCG-stimulated progesterone production by 26-37%. Concomitant treatment with IL-1 (1 ng/ml) did not further enhance the inhibitory effect of IFN gamma on HCG-stimulated progesterone production. In contrast, the combination of TNF alpha (1 ng/ml) and IFN gamma (10 ng/ml) acted synergistically to markedly inhibit HCG-stimulated progesterone production by 81%. In addition, IL-1 and TNF alpha, neither of which was effective alone, acted synergistically to reduce significantly HCG-stimulated progesterone production by 30%. The combination of TNF alpha and IFN gamma also markedly inhibited follicle stimulating hormone (FSH)-stimulated oestradiol production by 97%, a significantly greater inhibition than that obtained with either cytokine alone. These results suggest that the cytokines may interact to modulate the steroidogenic function of luteal cells in the developing corpus luteum.     

Evaluation of a test system for measuring cytokine production in human whole blood cell cultures

A simple and reproducible method is described for the measurement of mitogen-induced cytokine production in cultures of both human peripheral blood mononuclear cells (PBMC) and whole blood. In the culture supernatants the cytokines interleukin-1 alpha (IL-1 alpha), interleukin-2 (IL-2), interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) were determined by a rapid and sensitive immunoassay using various monoclonal and polyclonal antibodies. Comparing the PBMC cultures with the whole blood system a good correlation was obtained if the cell number was taken into account. In the post-induction supernatants the cytokine values were found to follow typical kinetic curves. The protocol was evaluated by screening 60 cancer patients with primary disease and 60 healthy controls. A markedly reduced secretion of IFN-gamma and IL-1 alpha was found in the cancer patients compared to controls, although leukocyte and lymphocyte counts were almost identical in both groups.     

A new highly sensitive immunoassay for cytokines by dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA).

Non-isotopic immunoassays for human tumor necrosis factor alpha (TNF alpha) and human interleukin-6 (IL-6) were established by employing the dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) system based on the time-resolved fluoroimmunoassay technique with europium-labeled antibody. Compared to enzyme-linked immunosorbent assays and bioassays, the sensitivity and range of measurement were significantly increased by applying the DELFIA systems to TNF alpha and IL-6. TNF alpha was measurable from 100 fg/ml to 10 ng/ml with the TNF alpha-DELFIA and IL-6 was measurable from 100 fg/ml to 1 ng/ml with the IL-6-DELFIA.     

Suppression by delta-9-tetrahydrocannabinol of interleukin 2-induced lymphocyte proliferation and lymphokine-activated killer cell activity

The major psychoactive marijuana component, delta-9-tetrahydrocannabinol (THC), suppressed proliferation of murine spleen cells stimulated with recombinant human interleukin 2 (IL-2) and also suppressed the appearance of the lymphokine-activated killer (LAK) cell phenomenon in IL-2-treated spleen cell preparations. Cell function was depressed in a dose-dependent manner with as little as 2.5 μg/ml THC (8μM). In addition, spleen cells previously stimulated in culture with IL-2 and then incubated with THC for 4 h prior to target cell addition, displayed suppressed cytolytic activity against both YAC-1 and EL-4 tumor targets. Killing of EL 4 cells was suppressd at lower drug doses than the killing of YAC-1 targets. These results suggest that THC can suppress several important functions of IL-2 including clonal expansion of lymphocytes, expansion of killer cell populations and stimulation of killer cell cytotoxic activity.     

Macrophage-like RAW 264 cell line and time-resolved fluoroimmunoassay (TRFIA) as tools in screening drug effects on cytokine secretion

A screening system was set up to study the effects of drugs on cytokine secretion by macrophages in vitro. The system is based on the murine macrophage-like cell line RAW 264, which can be activated with lipopolysaccharide (LPS) to produce cytokines. The responsiveness of the RAW 264 cells was outlined by challenging them with different concentrations of LPS for 6 or 24 h. Substantial time- and dose-dependent increases were recorded for interleukin-1 beta (IL-1β), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNFα) secretions. A general procedure was established to construct time-resolved fluoroimmunoassays (TRFIA) from commercial immunochemicals produced originally for enzyme immunoassays. Practical measuring ranges of the non-competitive assays were 100 pg/ml-10 ng/ml for 1L-1β and TNFα and 10 pg/ml-5 ng/ml for IL-6 and IL-5. The interleukin-5 (IL-5) assay was set up for unrelated human studies, but the others were used in the characterization of RAW 264 cytokine secretion. An immunosuppressive effect with dexamethasone phosphate could be achieved and recorded in the model system. Thus, the system offers a simple and easy-to-use model for screening immunomodulatory effects of drugs on the cytokine secretion of macrophages.     

Interleukin-1 alpha inhibits the effects of gamma-interferon and tumor necrosis factor alpha on the expression of the major histocompatibility antigens by the rat endothelium

Modulation of the major histocompatibility (MHC) antigen expression on rat endothelial cells by a mixture of cytokines has been examined. Experiments were performed employing both enzyme-linked immunoassay (ELISA) and fluorescence-activated cell-sorting (FACS) techniques and recombinant cytokines: interleukin-1 alpha (IL-1 alpha), tumor necrosis factor alpha (TNF alpha), and gamma-interferon (tau IFN). The results obtained show that TNF alpha enhances the effect of tau IFN on the expression of class I and II MHC antigens. IL-1 alpha did not affect tau IFN-induced class I expression but did inhibit tau IFN-induced class II expression. Finally, TNF alpha-induced class I MHC expression was inhibited strongly by IL-1 alpha. Pretreatment of endothelium with tau IFN did not potentiate the effects of IL-1 alpha or TNF alpha on the endothelial MHC antigen expression. These results suggest a possible anti-inflammatory role of IL-1 alpha via down-regulation of MHC antigen expression by the endothelium.     

Growth of murine natural killer cells from bone marrow in vitro: role of TNF alpha and IFN gamma.

It has been previously shown that natural killer (NK) cell growth can be induced by interleukin-2 (IL-2) in bone marrow (BM) cultures and that other cytokines (CKs), including IL-1 alpha, act synergistically with IL-2. However, as the effect of IL-2 and IL-1 alpha could be due to direct stimulation of NK progenitor cell growth, as well as to the induction of other factors, we analysed the role of the endogenous production of CKs in BM cultures. Results show that mRNAs specific for tumour necrosis factor-alpha (TNF alpha) and interferon-gamma (IFN gamma) are detectable within hours in BM cultures supplemented with IL-2 and IL-1 alpha, and that the amount is higher when both IL-2 and IL-1 alpha are present. Antibodies directed against TNF alpha and IFN gamma abrogate the NK cell development, indicating that these CKs play an essential role. The antibodies, however, had no effect on mature NK cells. Furthermore, pretreatment of BM cells with TNF alpha or IFN gamma before culturing with IL-2, enhances IL-2 responsiveness and NK cell growth. These results suggest that induction of cytokines production may be important for growth of NK cells from BM precursors and that the synergistic effect of IL-1 alpha could be due, at least in part, to increased TNF alpha and IFN gamma production.     

慢性丙型肝炎患者抗病毒治疗前PBMC细胞因子的研究

目的 研究准备抗病毒治疗的慢性丙型肝炎患者的免疫特点.方法 将30例慢性丙型肝炎患者和10例正常对照外周血单个核细胞(PBMC)体外培养72 h后,用ELISA法检测培养上清中细胞因子IL-2、IL-4、IL-10、IL-12、IFN-γ和TNF-α的浓度.结果 (1)慢性丙型肝炎患者PBMC培养上清中IFN-γ、IL-10和TNF-α的水平明显升高(P＜0.05),没有检测到IL-2、IL-4、IL-12的基础分泌.(2)不同病情患者间的细胞因子的分泌水平差异无统计学意义(P＞0.05).结论 慢性丙型肝炎患者体内TH2型细胞因子的分泌占优势.提示通过调整TH1/TH2失衡可能达到抗病毒治疗目的.     

The Effect of Cytokines on Expression of Glutamic Acid Decarboxylase-65 in Cultured Islets

Insulin dependent diabetes mellitus (IDDM) is an autoimmune disease characterized by lymphocytic infiltration of the pancreatic islets (insulitis). Cytokines released as part of the insulitis process have been suggested to play an important role in the beta cell lesion of IDDM. A possible diabetogenic effect of cytokines may be mediated by their inducing abnormal expression of islet cell autoantigens. Since glutamic acid decarboxylase-65 (GAD-65) is a target autoantigen in IDDM, we investigated whether the cytokines IL-1β, TNFα IFNγ altered islet cell expression of GAD-65 and whether the effect of cytokines on GAD-65 expression was similar to their effect on insulin secretion.

We found that: 1) IL-1β at low dose (1 U/ml) which stimulated insulin secretion, had no effect on GAD-65 expression, whereas higher doses of IL-1β (10, 100, 1000 U/ml) which inhibited insulin secretion, decreased GAD-65 expression. 2) TNFα at doses of 10, 100, 1000 U/ml which stimulated insulin secretion had no effect on GAD-65 expression. 3) IFNγ at doses of 10, 100, 1000 U/ml had no effect on insulin secretion or on GAD-65 expression. 4) In combination, IL-1β plus TNFα and IFNγ showed a similar inhibitory effect on GAD-65 expression as IL-1β alone.

In summary: 1) IL-1β dramatically inhibits GAD-65 expression. 2) TNFα and IFNγ have no effect on GAD-65 expression. Of these three cytokines, IL-1β is the primary cytokine affecting GAD-65 expression.     

Immunoglobulin D enhances the release of tumor necrosis factor-alpha, and interleukin-1 beta as well as interleukin-1 receptor antagonist from human mononuclear cells.

Immunoglobulin D (IgD) is normally present in only low concentrations in serum. In the hyper-IgD and periodic fever syndrome (HIDS), however, serum levels exceed 140 mg/l. This syndrome is further characterized by recurrent inflammatory febrile attacks together with an acute phase response and appearance of cytokines in the circulation. The role of IgD in the pathogenesis of HIDS and its relation to the increased cytokine concentrations is unclear. Therefore, we tested whether IgD, IgG and alpha 1-acid glycoprotein (AGP) isolated from human serum influence the synthesis of interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), and IL-1ra, as measured by specific radioimmunoassays, in human peripheral blood mononuclear cells (PBMC). Incubation of PBMC with IgD and AGP for 24 hr led to increased release of IL-1 beta, TNF-alpha, and IL-lra. The magnitude of stimulation of IgD exceeded that of AGP; the effect by IgD was dose-dependent and showed a 30-fold (TNF-alpha) to almost 150-fold (IL-1 beta) increase at the highest concentration (50 mg/l), while AGP (750 micrograms/ml) only increased the cytokine secretion fourfold (TNF-alpha) to almost 30-fold (IL-1 beta). The effect of IgD on IL-1ra was less dramatic but a fivefold increase was observed at 50 mg/l compared with a 2.5-fold increase with AGP. IgD potentiated the effect of lipopolysaccharide (LPS) on secretion of both IL-1 beta and TNF-alpha, although the effect was most apparent for TNF-alpha. Apart from inducing IL-1ra synthesis, IgG did not influence cytokine release in human PBMC. These data indicate that IgD is a potent inducer of TNF-alpha, IL-1 beta and IL-1ra and thus may contribute to the pathogenesis of HIDS.     

Synthetic surfactant (Exosurf) inhibits endotoxin-stimulated cytokine secretion by human alveolar macrophages.

Tumor necrosis factor-alpha (TNF), interleukin-1 beta (IL-1), interleukin-6 (IL-6), and interleukin-8 (IL-8) are inflammatory cytokines produced by alveolar macrophages (AMs) and implicated in sepsis-related adult respiratory distress syndrome (ARDS). Preliminary findings from clinical trials suggest that aerosolized delivery of the synthetic surfactant Exosurf (Burroughs Wellcome Co.) reduces mortality in patients with sepsis-induced ARDS. The purpose of the present study was to examine the effect of Exosurf on inflammatory cytokine secretion from AMs in vitro. AMs were obtained from normal nonsmoking adult volunteers. Secreted TNF, IL-1, IL-6, and IL-8 were measured by enzyme-linked immunoassays in 24 h culture fluids of AMs. Exosurf inhibited LPS-stimulated TNF, IL-1, and IL-6 secretion in a dose-dependent fashion. IL-8 secretion was not affected by Exosurf under these conditions. However, if AMs were preincubated for 24 h in media and then LPS-stimulated, IL-8 secretion was inhibited by Exosurf. Regulation of IL-8 production may differ from TNF, IL-1, and IL-6. Unstimulated cytokine secretion was not affected by any of the tested concentrations of Exosurf. The inhibitory effect of Exosurf on endotoxin-induced cytokine secretion by human AMs suggests that Exosurf may modulate inflammatory cytokine production in the lung.     

Cytokine secretion induced by superantigens in peripheral blood mononuclear cells, lamina propria lymphocytes, and intraepithelial lymphocytes.

Superantigens are potent inducers of T-cell proliferation and induce a broad range of cytokines, including tumor necrosis factor (TNF), gamma interferon, and interleukin 2 (IL-2). In the present study, we compared the abilities of different staphylococcal superantigens (staphylococcal enterotoxin B [SEB], staphylococcal enterotoxin E [SEE], and toxic shock syndrome toxin 1 [TSST-1]) to stimulate distinct cytokine profiles in peripheral blood mononuclear cells (PBMC), lamina propria lymphocytes (LPL), and intraepithelial lymphocytes (IEL). One million PBMC, LPL, and IEL were stimulated with various concentrations of superantigen (10 to 0.001 ng/ml) for 24, 48, and 72 h. Maximum cytokine production by PBMC, LPL, and IEL was observed for all three superantigens at 48 h at a concentration of 1 ng/ml. In PBMC, SEE and TSST-1 stimulated more IL-2 and gamma interferon than SEB. SEE and TSST-1 also stimulated more TNF and IL-4 production than SEB. In contrast, SEB stimulated more IL-6 than either SEE or TSST-1. In LPL, there was no SEE-induced IL-2 or IL-4 production, but IL-6, TNF, and gamma interferon were induced. SEB similarly induced no IL-2 or gamma interferon from the LPL, but IL-4, IL-6, and TNF were detected. TSST-1 stimulation of LPL resulted in IL-2 and TNF production but no IL-4, IL-6, or gamma interferon. In IEL, SEE induced no IL-2, IL-4, or gamma interferon but produced IL-6 and TNF, while SEB stimulation resulted in no IL-2 or gamma interferon but did result in detectable IL-4, IL-6, and TNF. Taken together, these data indicate that there are significant differences in the cytokine profiles induced by superantigens in LPL and IEL compared with those in PBMC, and these differences may relate to differences in activation requirements.     

Oral aspirin and ibuprofen increase cytokine-induced synthesis of IL-1 beta and of tumour necrosis factor-alpha ex vivo.

We investigated the effect of oral aspirin and ibuprofen on the ex vivo synthesis of interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-2, IL-6, tumour necrosis factor-alpha (TNF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) by stimulated peripheral blood mononuclear cells (PBMC) from healthy volunteers. Seven volunteers took 325 mg of aspirin daily for 14 days. Three weeks after ending aspirin medication, ex vivo IL-1 beta and TNF synthesis induced by exogenous IL-1 alpha was elevated threefold compared to the pre-aspirin value (P = 0.01 and P = 0.005, respectively). Using lipopolysaccharide (LPS) as a stimulus, no influence of oral aspirin was observed. The increase in cytokine synthesis did not parallel decreased synthesis of prostaglandin E2 (PGE2). Seven weeks after discontinuation of aspirin, cytokine and PGE-2 production returned to pre-aspirin levels. Another seven volunteers took 200 mg of ibuprofen daily for 12 days. Again, there was no effect on LPS- or Staphylococcus epidermidis-induced cytokine synthesis. However, IL-1 alpha-induced synthesis of IL-1 beta was elevated to a mean individual increase of 538% (P < 0.001) and synthesis of TNF was elevated to 270% (P < 0.001) at the end of ibuprofen medication and 2 weeks after discontinuation of ibuprofen. There were parallel increases in PGE2 and both returned to their pre-ibuprofen levels 5 weeks after stopping. Although inhibitors of cyclo-oxygenase blunt PGE2-mediated symptoms such as fever and pain, we conclude that short term use of either aspirin or ibuprofen results in a 'rebound' increase in cytokine-induced cytokine synthesis that is not observed in LPS-induced cytokines.     

Selective inhibition of natural killer but not natural cytotoxic activity in a cloned cell line by delta-9-tetrahydrocannabinol.

Natural killer (NK) and natural cytotoxic (NC) activities are spontaneously generated against certain tumors in vitro and their contribution to tumor immunity is being extensively investigated. We report here that the interleukin-2 (IL-2)-dependent murine cell line, NKB61A2, which we recently found to express both NK and NC functions, can be modulated selectively by 9 delta-tetrahydrocannabinol (THC). THC, a major psychoactive metabolite of marijuana, could significantly inhibit NK activity without altering NC activity in NKB61A2 cells. Inhibition of NK function occurred at a post-binding stage because effector/target conjugation was unaffected by THC. With regard to NC function, neither the cytotoxic activity of the cells nor release of tumor necrosis factor was interrupted by THC. Therefore, THC may provide a useful tool for dissociating the mechanism of NK and NC activities within a single population of cells.     

Characteristics of human synovial fibroblast activation by IL-1 beta and TNF alpha.

Human synovial fibroblast cell lines (HSN), established from tissues obtained from the knee joints of arthritis patients undergoing arthoplasty, were used to investigate the effects of human interleukin-1 (IL-1) beta and tumour necrosis factor (TNF)alpha on proliferation and prostaglandin E2 (PGE2) secretion. IL-1 beta and TNF alpha were equipotent stimulators of HSN proliferation. Classical non-steroidal anti-inflammatory drugs and glucocorticoids significantly augmented this effect. In addition, IL-1 beta and TNF alpha were potent inducers of PGE2 production while exogenous PGE2 was growth inhibiting. These data suggest that the secretion of PGE2 by monokine-stimulated HSN exerts a negative feedback signal. Further examination of IL-1 beta- and TNF alpha-induced PGE2 secretion revealed IL-1 beta to be a more potent stimulator; however, this observation may be due, in part, to differences in the kinetics of induction. Rabbit anti-IL-1 beta and anti-TNF alpha specifically neutralized both proliferation and PGE2 production induced by these monokines, but anti-IL-1 beta (or anti-IL-1 alpha) did not block TNF alpha activity. It is unclear whether TNF alpha stimulates HSN to produce IL-1, but the antibody data suggest that extracellular IL-1 is not responsible for TNF alpha in vitro activity.     

In Vitro Effect of Lycopene on Cytokine Production by Human Peripheral Blood Mononuclear Cells

There is evidence indicating that regular consumption of tomato products is associated with favorable immunomodulatory effects. In addition, tomato extracts have been shown to possess antioxidant, anticarcinogenic and antithrombotic activity in vitro.

Since tomatoes are rich in carotenoids and particularly in lycopene—the pigment responsible for the red color of tomatoes—the present work was designed to examine the in vitro effect of lycopene on cytokine production by peripheral blood mononuclear cells (PBMC) from 15 healthy subjects. First, 2 × 10⁶ PBMC suspended in 1 ml of conditioned medium were incubated over a period of 24 and 48 hours without or with the following concentrations of lycopene: 0.25, 0.5, 1.0, 2.0 and 4.0 μM. The production of the subsequent cytokines was evaluated: IL-1β, IL-1ra, IL-2, IL‐6 and IL-10, as well as TNFα and IFNγ. Lycopene induced a dose-dependent increase in IL1β, and TNFα production and a decrease in IL-2, IL-10 and IFNγ secretion, whereas that of IL-6 and IL-1ra was not affected. It is concluded that understanding the role of lycopene in modulation of the immune system may promote decisions as for dietary supplementation of lycopene for reducing the risk of certain diseases.     

Interleukin 2 leads to dose-dependent expression of the alpha chain of the IL-2 receptor on CD25-negative T lymphocytes in the absence of exogenous antigenic stimulation

Expression of the alpha chain of the interleukin 2 receptor on T lymphocytes is restricted, increasing in the setting of activation, particularly after antigenic stimulation via the TCR. The effects of IL-2 in vitro on the expression of CD25 and proliferation as well as the cytokine induction in CD25-depleted T cells were studied. CD25-depleted and PBMC of healthy donors were cultured for 7 days with 0, 10, or 100 IU/ml of IL-2. Phenotypic analysis and measurement of cytokines in the culture supernatants were performed. IL-2 led to a dose-dependent induction of the IL-2R alpha chain on both CD4 and CD8 T lymphocytes. In the CD25-depleted cultures, IL-2 treatment (100 IU/ml) increased the percentage of CD4 T cells expressing CD25 by 30.6% (P = 0.05) and of CD8 T cells by 48.2% (P = 0.01) on day 7 compared to no treatment. In the PBMC cultures the increase on day 7 was 36.4% for CD4 (P = 0.01) and 50.8% (P = 0.025) for CD8 T lymphocytes. The patterns of cytokine induction in the CD25-depleted and control cultures were similar with increases of IFN-gamma, GM-CSF, IL-16, TNF alpha, and soluble IL-2 receptor in the IL-2-containing cultures. CFSE experiments demonstrated the proliferative capacity of both CD25-positive and -negative T cells. Interleukin 2 alone can lead to a dose-dependent induction of the alpha chain of its receptor on resting CD4 and CD8 T lymphocytes. IL-2 as a sole stimulant is also associated with generation of a cytokine milieu that includes IFN-gamma, GM-CSF, IL-16, and TNF alpha.     

Induction of neutral proteinase and prostanoid production in bovine nasal chondrocytes by interleukin-1 and tumor necrosis factor alpha: modulation of these cellular responses by interleukin-6 and platelet-derived growth factor.

We have previously reported that recombinant human interleukin-1 (IL-1) stimulates matrix erosion in bovine nasal cartilage explants (R. J. Smith et al., Inflammation 13, 367-382, 1989). This action of IL-1 is believed to be caused by matrix-degrading neutral proteinases produced by activated chrondrocytes. Accordingly, we investigated the effects of recombinant human interleukin-1 alpha (IL-1 alpha), recombinant human interleukin-1 beta (IL-1 beta), and recombinant human tumor necrosis factor alpha (TNF alpha) on bovine nasal chondrocyte (BNC) responsiveness. IL-1 alpha and IL-1 beta stimulated a time (0-72 hr) and concentration-dependent (0.01-10 ng/ml) production of collagenase, gelatinase, caseinase, and prostaglandin E2 (PGE2) in BNC monolayer cultures. Neutral proteinase and PGE2 production by BNC was also induced by TNF alpha (0.2-200 ng/ml) in a time-dependent (0-72 hr) manner. Recombinant human interleukin-6 (IL-6) caused a concentration-dependent (6-200 ng/ml) potentiation of IL-1-stimulated neutral proteinase and PGE2 production by BNC. However, recombinant human platelet-derived growth factor homodimer BB suppressed BNC responsiveness to IL-1. A recombinant human IL-1 receptor antagonist protein inhibited BNC activation by IL-1 but not TNF alpha.     

Neopterin augmentation of tumor necrosis factor production

Gamma interferon (gamma-IFN), lipopolysaccharide (LPS)-gamma or interleukin-2 (IL-2)-induced tumor necrosis factor alpha (TNF alpha) production by both macrophages and peripheral blood mononuclear cells (PBMC), was increased in the presence of neopterin. Addition of neopterin caused an increased level of TNF alpha, but did not affect the kinetics of the TNF alpha production, which showed peak levels of cytotoxic activity 4 h after stimulatory treatment. Using anticytokine antibodies, we concluded that the neopterin effect was mainly gamma-IFN mediated, and only slightly affected by anti IL-2 receptor antibodies. The neopterin augmented TNF alpha production can be attributed to an immunological role for neopterin in the enhancement of cell-mediated immune (CMI) response.