Differential sensitivity to beta-cell secretagogues in cultured rat pancreatic islets exposed to human interleukin-1 beta

The early stages of insulin-dependent diabetes mellitus are characterized by a selective inability to secrete insulin in response to glucose, coupled to a better response to nonnutrient secretagogues. The deficient glucose response may be a result of the autoimmune process directed toward the beta-cells. Interleukin-1 (IL-1) has been suggested to be one possible mediator of immunological damage of the beta-cells. In the present study we characterized the sensitivity of beta-cells to different secretagogues after human recombinant IL-1 beta (rIL-1 beta) exposure. Furthermore, experiments were performed to clarify the biochemical mechanisms behind the defective insulin response observed in these islets. Rat pancreatic islets were isolated and kept in tissue culture (medium RPMI-1640 plus 10% calf serum) for 5 days. The islets were subsequently exposed to 60 pM human recombinant IL-1 beta during 48 h in the same culture conditions as above and examined immediately after IL-1 exposure. The rIL-1 beta-treated islets showed a marked reduction of glucose-stimulated insulin release. Stimulation with arginine plus different glucose concentrations, and leucine plus glutamine partially counteracted the rIL-1 beta-induced reduction of insulin release. The activities of the glycolytic enzymes hexokinase, glucokinase, and glyceraldehyde 3-phosphate dehydrogenase, were similar in control and IL-1-exposed islets. Treatment with IL-1 also did not impair the activities of NADH+- and NADPH+-dependent glutamate dehydrogenase, glutamate-aspartate transaminase, glutamate-alanine transaminase, citrate synthase, and NAD+-linked isocitrate dehydrogenase. The oxidation of D-[6-14C]glucose and L-[U-14C]leucine were decreased by 50% in IL-1-treated islets. Furthermore, there was a significant decrease in the ratios of [2-14C]pyruvate oxidation/[1-14C]pyruvate decarboxylation and L-[U-14C]leucine oxidation/L-[1-14C]leucine decarboxylation, indicating that IL-1 decreases the proportion of generated acetyl-coenzyme-A residues undergoing oxidation. However, in the presence of IL-1 there was a significant increase in L-[U-14C]glutamate oxidation. These combined observations suggest that exposure to IL-1 induces a preferential decrease in glucose-mediated insulin release and mitochondrial glucose metabolism. This mitochondrial dysfunction seems to reflect an impairment in proximal steps of the Krebs cycle. It is conceivable that the IL-1-induced suppression and shift in islet metabolism can be an explanation for the beta-cell insensitivity to glucose observed in the early phases of human and experimental insulin-dependent diabetes mellitus.

Auto-antibodies to tumour necrosis factor alpha in healthy humans and patients with inflammatory diseases and gram-negative bacterial infections

A semi-quantitative immunoblotting method was developed to screen for serum auto-antibodies against tumour necrosis factor alpha (TNF alpha). Forty nitrocellulose strips containing identical amounts of human recombinant TNF alpha (rTNF alpha) were prepared for each set-up, and the anti-TNF alpha antibody immunoreactivities were scored according to the density of the resulting colour reaction. A significant number of sera from apparently healthy donors contained detectable auto-antibodies to TNF alpha (40%), while the strongest reaction was observed in 8%. A higher prevalence of anti-TNF alpha antibodies was found in sera from patients with Gram-negative bacterial septicaemia (66%), cystic fibrosis with chronic Pseudomonas aeruginosa lung infection (72%), and various rheumatic diseases (61%). The antibodies in sera from these patients belonged primarily to the IgG and IgM classes, the latter exhibiting the strongest response. Longitudinally collected serum samples from patients in septic endotoxin shock revealed that the anti-TNF alpha antibodies were induced initially during septicaemia, reaching maximum reactivities within the first week and returning to low or undetectable levels on days 9-20.

Investigation of immunosuppressive properties of inactivated human immunodeficiency virus and possible neutralization of this effect by some patient sera

Retroviral infections are accompanied by immunosuppression in a variety of species. For feline leukemia virus, the immunosuppression has been ascribed to the transmembrane envelope protein, p15E, which suppresses the proliferative responses of cat, mouse, and human lymphocytes. A similar suppressive effect has been shown for a lysate of human immunodeficiency virus (HIV), strain HTLV-IIIB. Here we determined that detergent-disrupted HTLV-IIIB lystate exerted a strong suppressive effect on PHA-stimulated lymphocytes. Preparations of whole virions, a lysate of a local HIV isolate grown on MP-6 cells, and a commercially obtained UV and psoralene-inactivated lysate were examined and demonstrated to have a similar suppressive effect. The HIV lysate was not directly cytotoxic to lymphocytes and did not contain tumor necrosis factor or lymphotoxin. The HIV lysate specifically suppressed the proliferation of a range of hemopoietic cell lines from man and mouse including three EBV transformed CD4- and IL-2 receptor-negative B-cell lines. The lysate also suppressed the formation of human bone marrow colonies, whereas the lysate had only a slight or no effect on fibroblasts. The suppression of lymphocyte proliferation was not abrogated by addition of IL-2 or IL-1 and the HIV lysate inhibited the expression of IL-2 receptors on suboptimal PHA-stimulated mononuclear cells. The suppressive factor(s) has not been characterized in molecular terms, but suppressive activity was recovered in fractions with a molecular weight of about 67,000 and in both the glycoprotein fraction and in the glycoprotein-depleted fraction of the HIV lysate. Sera from one-third of a small series (N = 13) of individuals with antibodies to HIV seem to be able to neutralize the suppressive properties of HIV lysate in cultures.

Epidermal tumour necrosis factor alpha and interleukin 6-like activities in AIDS-related Kaposi's sarcoma. An immunohistological study

Biopsies from 6 patients with AIDS and Kaposi's sarcoma (KS) in the tumour stage, and 6 healthy controls, were immunohistologically examined for the presence of tissue-bound tumour necrosis factor alpha (TNF alpha) and interleukin 6 (IL-6) in the skin. TNF alpha was demonstrated using specific polyclonal antiserum to human recombinant TNF alpha. IL-6 was visualized indirectly using a polyclonal antiserum to partially purified human crude supernatants of activated human blood monocytes, followed by absorption with recombinant human IL-6. The cytokines were found identically located in epidermal cell membranes in stratum granulosum and spinosum of the epidermis from unaffected skin in both AIDS patients and in controls. Biopsies from KS elements showed markedly increased epidermal staining for both TNF delta and IL-6. It was not possible to detect TNF alpha or IL6 in the endothelial cells of the tumour. The observation of increased amounts of epidermal-bound TNF alpha and IL-6 in AIDS-related KS elements supplements previous studies indicating that the skin plays an active immunoinflammatory role in patients with AIDS.

Interleukin 6 primes human neutrophil and monocyte oxidative burst response

Interleukin 6 (IL-6), a 26-kDa inducible protein, is a cytokine with multiple biological activities. This paper reports on the regulatory role of rIL-6 on the function of human polymorphonuclear and mononuclear leukocytes, a property not described previously. rIL-6 by itself did not exhibit any chemotactic activity and it could not activate these cells for an oxidative burst response. Preincubation of both cell types with rIL-6 at concentrations of 5 and 50 ng/ml primed the cells for enhanced generation of oxygen radicals following stimulation with the chemotactic peptide f-Met-Leu-Phe or the phorbol ester PMA. The enhancement of the oxidative burst response occurred both at the level of superoxide anion generation, an early step in the activation pathway, and at the level of the hydrogen peroxide-myeloperoxidase mediated response, a later step in the oxidative burst pathway. The priming ability was abolished by heat treatment of rIL-6 at 100 degrees C but not at 70 degrees C. Stimulation of B cell growth and immunoglobulin production combined with enhancement of oxidative burst response of phagocytic cells by IL-6 provide an effective mechanism of fighting against invading micro-organisms.

Interleukin 6 primes human neutrophil and monocyte oxidative burst response

Interleukin 6 (IL-6), a 26-kDa inducible protein, is a cytokine with multiple biological activities. This paper reports on the regulatory role of rIL-6 on the function of human polymorphonuclear and mononuclear leukocytes, a property not described previously. rIL-6 by itself did not exhibit any chemotactic activity and it could not activate these cells for an oxidative burst response. Preincubation of both cell types with rIL-6 at concentrations of 5 and 50 ng/ml primed the cells for enhanced generation of oxygen radicals following stimulation with the chemotactic peptide f-Met-Leu-Phe or the phorbol ester PMA. The enhancement of the oxidative burst response occurred both at the level of superoxide anion generation, an early step in the activation pathway, and at the level of the hydrogen peroxide-myeloperoxidase mediated response, a later step in the oxidative burst pathway. The priming ability was abolished by heat treatment of rIL-6 at 100 degrees C but not at 70 degrees C. Stimulation of B cell growth and immunoglobulin production combined with enhancement of oxidative burst response of phagocytic cells by IL-6 provide an effective mechanism of fighting against invading micro-organisms.

IgG autoantibodies against interleukin 1 alpha in sera of normal individuals

A pool of human sera from healthy blood donors was found to interfere competitively with the binding of 125I-labelled human recombinant interleukin 1 alpha (rIL-1 alpha) to the murine T-cell line EL4. The interference was reversible at the cellular level, and direct binding of the ligand to serum factors was therefore investigated. After preincubation of [125I]rIL-1 alpha with pooled serum, the 125I activity eluted in two peaks from a Sephadex G-75 column. The first was located in the void volume. The second eluted together with monomer rIL-1 alpha. An almost complete displacement of the high molecular weight 125I fraction was achieved with an excess of unlabelled rIL-1 alpha but not with rIL-1 beta. The serum factors binding to [125I]rIL-1 alpha were located in the molecular weight range 100,000-200,000, judged by fractionation on a Sephacryl S-400 column, and the factors were bound to immobilized protein A. Furthermore, [125I]rIL-1 alpha preincubated with serum co-precipitated with a specific rabbit anti-human IgG antibody. Screening of 29 sera from normal individuals showed similar effects in three cases. We conclude that approximately 10% of normal human sera contains detectable IgG autoantibodies to IL-1 alpha.

Studies on the mechanisms causing inhibition of insulin secretion in rat pancreatic islets exposed to human interleukin-1 beta indicate a perturbation in the mitochondrial function

This study aimed at a more detailed characterization of the mechanisms by which interleukin 1 (IL-1) inhibits insulin secretion. For this purpose, isolated rat pancreatic islets were kept in tissue culture for 5 days in medium RPMI 1640 plus 10% calf serum. The islets were subsequently transferred to the same culture medium containing various test substances plus 1% human serum with or without 25 U/ml human recombinant IL-1 beta. After a culture period of 48 h the islet structure was examined in the electron microscope and the islet function studied in short term incubations in the absence of IL-1. Islets exposed to IL-1 showed ultrastructural signs of degeneration in 10-20% of the B cells while such changes were not found in other types of islet cells. An increased number of secondary lysosomes and occasional myelin figures were observed in the B cells exposed to IL-1. These ultrastructural alterations were, however, reversed in islets cultured in cytokine-free medium for 6 days after the IL-1 treatment. In islets cultured in the presence of 11.1 mM glucose only, or 11.1 mM glucose plus 10 mM nicotinamide, 61 mM dimethyl area, 2 micrograms/ml indomethacin, 10 microM 4-bromophenacyl bromide or 10 microM nordihydroguaiaretic acid, 10 microM phenantroline, and 0.1 or 1.0 microgram/ml cyclosporin A, IL-1 reduced the insulin release by 64-85%. Culture at 5.6 mM glucose did not modify the IL-1-induced inhibition of insulin release, whereas a significant protective effect was observed at 28 or 56 mM glucose. The DNA content in IL-1-exposed islets cultured at 11.1 mM glucose was decreased by about 20% but not in islets cultured at other glucose concentrations. The D-[5-3H]glucose utilization at 16.7 mM glucose was unaffected by IL-1, whereas the oxidation of D-[6-14C]glucose was reduced by 50%. The present results suggest that IL-1-induced inhibition of insulin secretion is related to a disturbed mitochondrial function. This effect is not counteracted by a poly(ADP-ribose) synthetase inhibitor, a hydroxyl radical scavenger, an iron chelator, a T lymphocyte-specific immunosuppressive drug, or inhibitors of phospholipase A2 or inhibitors of prostaglandin and leukotriene synthesis. Thus, IL-1-induced inhibition of insulin secretion seems not to be mediated by the same mechanisms as those causing alloxan- or streptozotocin-induced damage of B cells. Furthermore, the action of IL-1 does not appear to be mediated via arachidonic acid metabolism. Glucose affords some protection, probably by enhancing the B cell mitochondrial function.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunochemical and biological reactivity of human anti-lipopolysaccharide IgG obtained by screening of blood donors

An anti-lipopolysaccharide (LPS) preparation for the intravenous treatment of septic endotoxic shock was prepared by purifying immunoglobulin G (IgG) from pooled serum from Danish blood donors. The sera were selected by the use of an enzyme-linked immunosorbent assay (ELISA) to screen blood donors for high concentrations of antibodies to a mixture of LPS from 11 different Gram-negative bacteria. ELISA was also used for indirect quantification of IgG antibodies to lipid A, and to rough LPS from Escherichia coli Ra and Salmonella minnesota R60 (Ra). The concentration of human antibodies to the LPS mixture correlated with the concentration of antibodies to the E. coli and S. minnesota rough LPS and to lipid A. The specificity of sera with high concentrations of anti-LPS IgG was investigated by immunoblotting. Sera from individual donors reacted with LPS from different bacteria and recognized different sites on the LPS molecules. The range of specificities to different LPS was increased by the pooling of selected sera. The IgG fraction from the high titre donor pool neutralized biological activities of LPS such as activation of the Limulus amoebocyte lysate reaction and induction of tumour necrosis factor secretion from human monocytes.

Association between HLA-DR2 and production of tumour necrosis factor alpha and interleukin 1 by mononuclear cells activated by lipopolysaccharide

The production of tumour necrosis factor (TNF) and interleukin 1 (IL-1) by lipopolysaccharide-activated mononuclear cells from 39 healthy donors was studied in vitro by bioassay and ELISA. The donors were typed for HLA-A, -B, -C, -DR, and -DP antigens. There was no detectable production of TNF beta (lymphotoxin). The intracellular levels of bioactive TNF alpha were minimal or undetectable in all cases. Cells from HLA-DR2+ individuals secreted significantly lower amounts of TNF alpha than cells from HLA-DR2- donors [2 ng/ml (1.5-4.4) and 7.5 ng/ml (3.9-8.3) respectively (medians 25-75%); P less than 0.01]. The difference disappeared if the cells were preactivated for 2 days with 1000 U/ml of recombinant gamma interferon (rIFN-gamma). In some individuals, the TNF alpha response increased considerably after IFN-gamma priming, in particular in those possessing the HLA-DR2 antigen. In contrast, there was no detectable difference in the production of IL-1 beta between the donors, and the IL-1 beta response decreased significantly after rIFN-gamma priming in HLA-DR2+ individuals [2.3 ng/ml (1.1-8.4) versus 7.2 ng/ml (5-7.9); P less than 0.05] and in HLA-DR2- individuals [3 ng/ml (1.1-5.3) versus 5.7 ng/ml (3.9-7.5); P less than 0.01]. There was no correlation between the TNF alpha and IL-1 responses and any of the other HLA-DR, -DP, or -B antigens. There was a significant positive correlation between the levels of TNF alpha measured by ELISA and by cytotoxicity assay. However, the TNF alpha-containing supernatants from 9 out of 37 individuals appeared to contain inhibitor(s) of the biological activity of TNF alpha. The presence of inhibitor(s) was not associated with any HLA antigens.

Effects of natural and recombinant interleukin-1 alpha and -beta on cytosolic free calcium in human and murine fibroblasts

Changes in the concentration of cytosolic free calcium ((Ca2+)i) in response to purified blood monocyte IL-1 and human rIL-1 alpha and rIL-1 beta (17.5 kDa) were measured in murine L-M fibroblasts and in human foreskin fibroblasts using the fluorescent Ca2+ indicator, fura-2. In L-M fibroblasts, each of these IL-1 species, but not a recombinant 24-kDa precursor of the predominant IL-1 beta, produced a prompt, dose-related, and transient increase in (Ca2+)i. The effect was smaller but not eliminated when the cells were stimulated in EGTA-containing calcium, suggesting that the rise in (Ca2+)i was due to influx from both intracellular and extracellular Ca2+ pools. In human fibroblasts, however, the (Ca2+)i increased gradually, reaching a maximum after 1 hr of incubation with IL-1 and returning slowly to near basal levels in the following 2 hr. In contrast to the L-M cells, this accumulation of Ca2+ was abolished by EGTA, suggesting that in human fibroblasts, Ca2+ is mobilized solely from the extracellular space. Addition of the Ca2+ channel blockers verapamil and nifedipine was ineffective. IL-1 alpha and IL-1 beta both induced a dose-related increase in prostaglandin E2, but only in the human fibroblasts. These findings indicate that an increase in (Ca2+)i may be an important second mediator by which IL-1 initiates cell activation, but the signal may differ between cells.

Modulation of human neutrophil and monocyte chemotaxis and superoxide responses by recombinant TNF-alpha and GM-CSF

The effects of recombinant TNF and GM-CSF on human peripheral blood neutrophil and monocyte chemotaxis and the superoxide response were studied. TNF exhibited a slight chemotactic activity for both cell types. Preincubation of neutrophils with as little as 40 units/ml strongly inhibited the neutrophil chemotaxis towards f-Met-Leu-Phe. The inhibition of monocyte chemotaxis required higher concentrations of TNF (greater than 400 units/ml). TNF at concentrations higher than 500 units/ml enhanced the generation of superoxide anions by neutrophils stimulated with f-Met-Leu-Phe. In contrast, TNF even at 2,000 units/ml did not prime monocytes for enhanced superoxide response. GM-CSF alone did not exhibit any chemotactic activity for any of the cell types tested. Preincubation of cells with GM-CSF inhibited chemotaxis of neutrophils but not of monocytes. GM-CSF was as potent as TNF in enhancing the generation of superoxide response by neutrophils. However, GM-CSF did not have any effect on monocyte superoxide response. The priming ability of TNF and GM-CSF on neutrophils was heat-sensitive. We conclude that TNF and GM-CSF play a more pronounced regulatory role on neutrophils than on monocytes. Inhibition of neutrophil chemotaxis followed by enhancement of the superoxide response by TNF and GM-CSF may provide an attractive mechanism by which these cytokines assist in fighting invading microorganisms.

Interleukin-1 affects the function of cultured human thyroid cells

Cytokines are peptide hormones essential for cellular communication in the immune response. The purpose of this study was to investigate the influence of cytokines, especially recombinant interleukin 1 beta (rIL-1 beta), on human thyroid cells. Thyroglobulin (Tg) was measured by a double antibody radioimmunoassay, and cyclic AMP (cAMP) by a competitive protein binding assay. Supernatants from unstimulated and phytohaemagglutinin-stimulated blood mononuclear cells were added to human thyroid cells cultured in monolayers. A dose-dependent inhibition of the secretion of Tg and cAMP was demonstrated. Both subcultured and primary cultured cells incubated with rIL-1 beta at pharmacological levels (10(-1)-10(2) U/ml) exhibited an inhibition of Tg and cAMP secretion, while at physiological levels (10(-5)-10(-3) U/ml), the secretion of Tg was enhanced. The similar stimulation of cAMP was demonstrated in subcultures. These in vitro studies suggest that IL-1 beta may play a role in the pathogenesis of autoimmune thyroid diseases. Further, the stimulations at low concentrations indicate that IL-1 beta may regulate the function of the thyroid gland under physiological conditions.

Inhibition of human lymphocyte proliferation and cleavage of interleukin-2 by Pseudomonas aeruginosa proteases

This study was undertaken to determine the effect of Pseudomonas aeruginosa alkaline protease (AP) and elastase (ELA) on human lymphocyte function. AP at 50 micrograms/ml and ELA at 12 micrograms/ml caused a 50% inhibition of phytohemagglutinin-induced proliferation. There was no difference in the effect of proteases on CD4- and CD8-positive cells. To determine the effect of proteases on interleukin-2 (IL-2)-induced cell proliferation, the proteases and IL-2 were added to the IL-2-dependent CTLL-2 cell line. AP and ELA inhibited the proliferation of these cells. When IL-2 was added in excess, the inhibition was partly reversed. ELA at 10 micrograms/ml cleaved IL-2, as judged by size chromatography of a reaction mixture containing 125I-labeled IL-2 and the proteases. The ELA-digested IL-2 exhibited a reduced binding capacity to IL-2 receptors on the lymphocytes. Furthermore, treatment of phytohemagglutinin-stimulated lymphocytes with AP and ELA resulted in inhibition of binding of intact IL-2 to IL-2 receptors on the stimulated lymphocytes. These results indicated that P. aeruginosa-derived enzymes are able to interfere with human lymphocyte function in vitro and that this effect might be due to cleavage of IL-2.

Functional characteristics of rat pancreatic islets maintained in culture after exposure to human interleukin 1

Recent observations suggest a role for interleukin 1 beta (IL-1) in the autoimmune beta-cell destruction observed in type I (insulin-dependent) diabetes mellitus. We investigated the acute and long-term effects of IL-1 on pancreatic beta-cell function in vitro. Rat pancreatic islets were isolated and kept in tissue culture for 5 days. The islets were subsequently transferred to media containing RPMI-1640 plus 1% human serum with or without human recombinant IL-1 beta (300 pM) and cultured for another 48 h. The islets were examined either immediately after IL-1 exposure (day 0) or after an additional 6-day culture period without IL-1. On day 0, IL-1 was found to totally inhibit glucose-stimulated insulin release, partially inhibit glucose oxidation, and induce a decrease in islet DNA content. However, these islets were able to release insulin after stimulation with glucose plus theophylline, although the absolute rate of insulin secretion was lower than that of the control group. After 6 days in culture, the insulin-secretory response to glucose and the glucose oxidation rates of the IL-1-pretreated islets were completely restored, but there remained a reduced islet DNA content. We conclude that IL-1 is cytotoxic to islet beta-cells. However, surviving beta-cells are able to recover their functional capacity after a period of inhibited function.

Modulation of natural killer cell activity in peripheral blood by physical exercise

The present study was designed to examine the effect of physical exercise on human natural killer (NK) cells. Six healthy volunteers underwent two different acute physical exercise tests with an interval of at least 1 week: (1) 60 min bicycle exercise at 80% of maximal oxygen uptake (VO2max) and (2) 60 min back-muscle training at up to 29% of VO2max; blood samples were collected before and during the last few minutes of exercise, as well as 2 h and 24 h afterwards. The NK cell activity (lysis/fixed number of mononuclear cells) increased during bicycle exercise, dropped to a minimum 2 h later and returned to pre-exercise levels within 24 h. Back-muscle exercise did not significantly influence NK cell activity. Plasma levels of adrenaline, noradrenaline, and cortisol were elevated during bicycling, but not during back-muscle exercise, indicating that exercise intensity is a determinant of NK cell activity. During bicycle exercise the NK cell subset (CD16- cells) of mononuclear cells increased significantly. Furthermore an improved interleukin 2 (IL-2) boosting of the NK cell activity was found during work as compared to IFN-alpha and indomethacin-enhanced NK cell activity. These results indicate that NK cells with a high IL-2 response capacity are recruited to the peripheral blood during exercise. The decreased NK cell activity demonstrated 2 h after work was probably not due to fluctuations in size of the NK cell pool, since the proportion of CD16+ cells was normal. The finding that indomethacin fully restored the suppressed NK cell activity in vitro and the demonstration of a twofold increase in monocyte (CD20+ cells) proportions 2 h after work, strongly indicate that prostaglandins released by monocytes during the heavy physical exercise are responsible for the down-regulation of the NK cells.

Interleukin 1-induced down-regulation of antibody binding to CD4 molecules on human lymphocytes

Interleukin 1 (IL-1) is involved in the early activation of T lymphocytes. The CD4 antigen, described as a phenotypic marker of helper T cells, is also important in early T-cell activation by its ability to bind to MHC class II molecules on antigen-presenting cells, and to transmit positive (and negative) signals to the cells. We observed that purified human monocyte IL-1 as well as recombinant IL-1 alpha and IL-1 beta selectively decreased the binding of monoclonal antibodies to CD4 on the surface of otherwise unstimulated blood T cells, in contrast to prestimulated and continuously grown CD4+ cells. Under optimal growth conditions, the initial reduction in antibody binding to CD4 was followed by an apparent re-expression of the CD4 antigen even in the presence of high concentrations of IL-1. This re-expression did not occur if the cells were cultured at 4 degrees C, or after treatment with actinomycin D or cytochalasin B, indicating that protein synthesis and intact microfilament function were essential for re-expression of CD4 binding. The mechanism by which CD4 molecules are physically and/or functionally modulated by IL-1 is unclear.

Inhibitor of interleukin 1 in normal human urine. Different effects on mouse thymocytes and on a murine T-cell line

We investigated whether urine from normal individuals contains inhibitors of interleukin 1 (IL-1). Diafiltered urine from normal afebrile donors suppressed IL-1-induced interleukin 2 (IL-2) activity of mouse thymocyte supernatants. These supernatants, however, strongly suppressed IL-2-induced [3H]thymidine incorporation into the IL-2-sensitive cell line CTLL-2, whereas the urine preparations did not. This phenomenon was caused by an increased amount of thymidine secreted by the urine-treated thymocytes. Therefore, in order to prevent interference, experiments were carried out with excess [3H]thymidine. Under these circumstances, suppression of IL-1- and to a lesser extent IL-2-induced DNA synthesis was still observed, whereas the synergistic effect of IL-1 on IL-2-induced DNA synthesis was only marginally reduced. We conclude that suppression of IL-1-induced IL-2 production by mouse thymocytes is a major effect of the IL-1-inhibitory factor(s) in normal urine. When the murine EL4 cell line was used, the diafiltered urine failed to inhibit IL-1-induced IL-2 production. The detection of an IL-1 inhibitor in urine is therefore dependent on the target cells as well as the effects of IL-1 on these cells.

Recombinant interleukin 1 alpha and beta prime human monocyte superoxide production but have no effect on chemotaxis and oxidative burst response of neutrophils

We report that recombinant human IL 1 alpha and beta and the two synthetic short fragments 163-171 and 226-254 do not exhibit chemotactic activity for human peripheral blood neutrophils and monocytes. These products up to concentrations of 4 X 10(4) units/ml failed to show chemotactic activity. Furthermore, IL 1 alpha and beta failed to generate chemotactic factors from human serum. Recombinant IL 1 alpha, IL 1 beta, or IL 1 beta fragments 163-171 and 226-254 did not induce any superoxide response by monocytes or neutrophils. However, exposure of monocytes to recombinant IL 1 alpha or IL 1 beta resulted in enhanced generation of superoxide response following stimulation with PMA. No priming was observed in neutrophils. These results suggest that IL 1 alpha and beta are involved in regulation of monocyte oxidative burst response, but play no direct regulatory role on neutrophil function.

1 alpha,25-Dihydroxyvitamin D3 and a novel vitamin D analogue MC 903 are potent inhibitors of human interleukin 1 in vitro

1 alpha,25-dihydroxycholecalciferol (1,25(OH)2D3) inhibits the lymphocyte growth hormone, interleukin 2. Since its production is dependent upon interleukin 1 (IL-1) produced by antigen-presenting cells, we tested five vitamin D3 analogues for effects on the production and function of human natural and recombinant IL-1. The production was not affected, but 1,25(OH)2D3 (greater than 10(-11) M) and a synthetic derivative MC 903 (greater than = 10(-10) M) inhibited the proliferation of mouse thymocytes to IL-1. The vitamins failed to affect the cytotoxic activity of tumor necrosis factor. 1,25(OH)2D3 may play a physiological immunomodulatory role as a selective inhibitor of the function of IL-1, and MC 903 may prove clinically useful in this regard because of its limited calcium metabolic activity.

Immunohistological detection of interleukin I-like molecules and tumour necrosis factor in human epidermis before and after UVB-irradiation in vivo

Skin biopsies from five healthy subjects, taken before and after UVB irradiation, were examined using immunohistological techniques for the cytokines interleukin-I (IL-I) and tumour necrosis factor (TNF). Using polyclonal specific antibodies against IL-I and TNF, the two cytokines appeared identically located on the epidermal cell membranes of the stratum granulosum and stratum spinosum in unexposed skin. After UVB-exposure, the staining intensity for both IL-I/epidermal cell derived thymocyte-activating factor (ETAF) and TNF was markedly increased, and the epidermal staining included the basal cell layer. Immunohistological investigation of tissue-bound epidermal cytokines may be valuable in the study of skin diseases.