Protection from septic shock by neutralization of macrophage migration inhibitory factor.

Identification of new therapeutic targets for the management of septic shock remains imperative as all investigational therapies, including anti-tumor necrosis factor (TNF) and anti-interleukin (IL)-1 agents, have uniformly failed to lower the mortality of critically ill patients with severe sepsis. We report here that macrophage migration inhibitory factor (MIF) is a critical mediator of septic shock. High concentrations of MIF were detected in the peritoneal exudate fluid and in the systemic circulation of mice with bacterial peritonitis. Experiments performed in TNFalpha knockout mice allowed a direct evaluation of the part played by MIF in sepsis in the absence of this pivotal cytokine of inflammation. Anti-MIF antibody protected TNFalpha knockout from lethal peritonitis induced by cecal ligation and puncture (CLP), providing evidence of an intrinsic contribution of MIF to the pathogenesis of sepsis. Anti-MIF antibody also protected normal mice from lethal peritonitis induced by both CLP and Escherichia coli, even when treatment was started up to 8 hours after CLP. Conversely, co-injection of recombinant MIF and E. coli markedly increased the lethality of peritonitis. Finally, high concentrations of MIF were detected in the plasma of patients with severe sepsis or septic shock. These studies define a critical part for MIF in the pathogenesis of septic shock and identify a new target for therapeutic intervention.

Mast cells control neutrophil recruitment during T cell-mediated delayed-type hypersensitivity reactions through tumor necrosis factor and macrophage inflammatory protein 2.

Polymorphonuclear leukocytes (PMNs) characterize the pathology of T cell-mediated autoimmune diseases and delayed-type hypersensitivity reactions (DTHRs) in the skin, joints, and gut, but are absent in T cell-mediated autoimmune diseases of the brain or pancreas. All of these reactions are mediated by interferon gamma-producing type 1 T cells and produce a similar pattern of cytokines. Thus, the cells and mediators responsible for the PMN recruitment into skin, joints, or gut during DTHRs remain unknown. Analyzing hapten-induced DTHRs of the skin, we found that mast cells determine the T cell-dependent PMN recruitment through two mediators, tumor necrosis factor (TNF) and the CXC chemokine macrophage inflammatory protein 2 (MIP-2), the functional analogue of human interleukin 8. Extractable MIP-2 protein was abundant during DTHRs in and around mast cells of wild-type (WT) mice but absent in mast cell-deficient WBB6F(1)-Kit(W)/Kit(W-)(v) (Kit(W)/Kit(W)(-v)) mice. T cell-dependent PMN recruitment was reduced >60% by anti-MIP-2 antibodies and >80% in mast cell-deficient Kit(W)/Kit(W)(-v) mice. Mast cells from WT mice efficiently restored DTHRs and MIP-2-dependent PMN recruitment in Kit(W)/Kit(W)-(v) mice, whereas mast cells from TNF(-/)- mice did not. Thus, mast cell-derived TNF and MIP-2 ultimately determine the pattern of infiltrating cells during T cell-mediated DTHRs.

The c-kit ligand, stem cell factor, can enhance innate immunity through effects on mast cells.

Mast cells are thought to contribute significantly to the pathology and mortality associated with anaphylaxis and other allergic disorders. However, studies using genetically mast cell-deficient WBB6F1-KitW/KitW-v and congenic wild-type (WBB6F1-+/+) mice indicate that mast cells can also promote health, by participating in natural immune responses to bacterial infection. We previously reported that repetitive administration of the c-kit ligand, stem cell factor (SCF), can increase mast cell numbers in normal mice in vivo. In vitro studies have indicated that SCF can also modulate mast cell effector function. We now report that treatment with SCF can significantly improve the survival of normal C57BL/6 mice in a model of acute bacterial peritonitis, cecal ligation and puncture (CLP). Experiments in mast cell-reconstituted WBB6F1-KitW/KitW-v mice indicate that this effect of SCF treatment reflects, at least in part, the actions of SCF on mast cells. Repetitive administration of SCF also can enhance survival in mice that genetically lack tumor necrosis factor (TNF)-alpha, demonstrating that the ability of SCF treatment to improve survival after CLP does not solely reflect effects of SCF on mast cell- dependent (or -independent) production of TNF-alpha. These findings identify c-kit and mast cells as potential therapeutic targets for enhancing innate immune responses.

Mast cell growth-enhancing activity (MEA) stimulates interleukin 6 production in a mouse bone marrow-derived mast cell line and a malignant subline.

A novel mast cell growth-enhancing activity (MEA/P40/interleukin 9 [IL-9]) purified from the conditioned medium of a murine interleukin 2 (IL-2)-dependent Mlsa-specific T-cell line (MLS4.2) was tested for its capacity to induce interleukin 6 (IL-6) production in a mouse bone marrow-derived factor-dependent mast cell line (L138.8A). This interleukin 3 (IL-3)/interleukin 4 (IL-4)/MEA-responsive cell line was demonstrated recently to express IL-6 mRNA and to secrete IL-6 when cultured with IL-3/IL-4. Now we were able to show that conditioned medium from L138.8A mast cells stimulated with MEA alone contained growth factor activity for the IL-6-dependent mouse hybridoma cell line 7TD1 that was completely blocked by the monoclonal anti-IL-6 antibody 6B4. A dose-response study including IL-3, IL-4, and MEA tested either alone or in different combinations revealed that among these growth factors MEA was the most potent inducer of IL-6 in L138.8A cells. Moreover, IL-4 but not IL-3 had a strong synergistic effect on MEA-induced IL-6 production. The autonomous malignant mast cell subline L138Cauto also showed enhanced IL-6 production when stimulated with MEA. Our findings indicate that MEA (IL-9) not only provides a proliferation signal, but also leads to a marked functional activation of responsive mast cells.

The role of the spleen in a lactate dehydrogenase mutant mouse (Ldh-1c/Ldh-1c) with hemolytic anemia.

The lactate dehydrogenase mouse mutant Ldh-1c/Ldh-1c is afflicted with a severe hemolytic anemia associated with extreme reticulocytosis (95%) and splenomegaly. Ninety-one percent of the total body colony-forming units--erythroid (CFU-E) have been quantified in the seven- to ten-times enlarged spleens of the mutant mice. Moreover, the splenic fraction of morphologically recognizable erythroid precursors was 134 times normal. From these data it was apparent that the spleen crucially contributes to the maintenance of steady state erythropoiesis in the mutants. On the other hand, an enhanced sequestration of red blood cells in the enlarged spleen may augment the anemia. Splenectomy experiments were performed with LDH mutant and wild type mice in order to investigate the role of the spleen in this particular hemolytic disease. Following splenectomy, the peripheral blood values and the frequency of femoral stem and progenitor cells were determined, and histological investigations were carried out. The life span of the splenectomized mutants was not shortened, in spite of a very low red blood cell count (25% of the untreated mutant value). Compared to the splenic loss only a moderate increase in bone marrow erythropoiesis was observed, such as a 250% increase of CFU-E. It is concluded that the reduction in red blood cell survival due to splenic sequestration in the mutants is of such a magnitude that it counterbalances a significant portion of splenic erythropoiesis.

The response of murine splenic granulocyte-macrophage colony-forming cells to lipid A in vivo.

The physical and biological properties of murine splenic granulocyte-macrophage colony-forming cells (GM-CFC) were analyzed after the injection of the splenic hemopoiesis stimulating agent lipid A. In continuous gradients of Percoll, the majority of the splenic GM-CFC of untreated mice peaked at a buoyant density of 1.090 g/cm3, while a small second GM-CFC peak could be detected at 1.065 g/cm3. One day after the injection of lipid A, the splenic GM-CFC were almost equally distributed among these two density peaks. This altered proportion was still detectable 72 to 96 h later, although to a smaller extent. No difference in the responsiveness to the colony-stimulating factor (GM-CSF) from mouse-lung conditioned medium (MLCM) was observed between these two density subpopulations. The differentiation pattern of splenic GM-CFC was altered after the injection of lipid A. However, this altered pattern was the same in both density subpopulations. The percentage of splenic GM-CFC as well as the percentage of multipotent hemopoietic stem cells (CFUs) in DNA synthesis were markedly elevated after the injection of lipid A. A striking difference in the proliferative activity was found between high- and low-density GM-CFC in post-lipid A spleens. 24 h after the injection of lipid A, 43% of the high-density GM-CFC subpopulation was found in S according to the suicide technique using tritiated thymidine, whereas in the low-density fraction only 10% of the population was killed. This finding allows alternative interpretations.

The effect of two different types of colony-stimulating factor on the expression of aminopeptidase on marrow-derived murine macrophages.

The expression of aminopeptidase, a surface-membrane-bound enzyme, on macrophages formed in liquid cultures of hemopoietic progenitor cells was studied over a period of 20 days. The cultures were stimulated by two biochemically distinct types of colony-stimulating factor (CSF) derived from mouse-lung-conditioned medium (MLCM) and L-cell-conditioned medium (LCCM), respectively. The enzyme content of single cells was determined microphotometrically after staining with Fast Blue B salt and leucine 4-methoxy-2-naphthylamide. In LCCM-stimulated cultures the number of cells expressing aminopeptidase, the enzyme content per cell and the enzyme concentration increased markedly from day 10 onward, while macrophages from MLCM-stimulated cultures only showed borderline yet significantly positive aminopeptidase levels. Maximum enzyme concentrations were found earlier than maximum enzyme content indicating an early local increase in the aminopeptidase concentration on the membrane and subsequently a more uniform distribution over the cell surface. The two types of CSF differ not only in their effect on macrophage production but also in their influence on the expression of the surface enzyme aminopeptidase on these cells.

Recombinant murine interleukin 9 enhances the erythropoietin-dependent colony formation of human BFU-E.

Murine interleukin 9 (mIL-9) is a novel T-cell-derived lymphokine previously described as a T-cell growth factor (P40/TCGFIII) and as a mast cell growth-enhancing activity (MEA). In the present study we examined the potency of recombinant (r)mIL-9 to exhibit hemopoietic growth factor activity in the human system. In semisolid cultures of normal human bone marrow-derived mononuclear cells, rmIL-9 alone at a concentration range from 25 to 200 U/ml did not reveal any colony-stimulating activity on human granulocyte-macrophage colony-forming cells (GM-CFC), erythroid colony-forming units (CFU-E), and erythroid burst-forming units (BFU-E). Furthermore, we did not observe synergistic effects of rmIL-9 on the number, size, and morphological composition of human granulocyte-macrophage colonies in cultures stimulated with giant cell tumor-conditioned medium. However, a synergistic effect of rmIL-9 in the human erythropoietic culture system was clearly demonstrated in the presence of recombinant human erythropoietin (rhEpo). Recombinant murine IL-9 at a concentration of 200 U/ml enhanced the number of BFU-E-derived day-14 colonies about 3.6-fold as compared to control cultures stimulated with Epo alone. The formation of CFU-E-derived day-7 colonies was not significantly altered under the same conditions. Our results demonstrate that in the presence of rhEpo, rmIL-9 is synergistically active in human bone marrow cultures as an erythroid burst-promoting factor. The development of granulocyte-macrophage colonies obviously is not affected. This finding strongly suggests that mIL-9 can mediate signals via human IL-9 receptors and further extends the range of biological activities hitherto ascribed to mIL-9.

Constitutive and modulated cytokine expression in two permanent human bone marrow stromal cell lines.

We present a detailed analysis of cytokine expression patterns of the two permanent human bone marrow stromal cell lines, L87/4 and L88/5. These cell lines, previously established in our laboratory, are highly radiotolerant without cell detachment and support long-term cultures of CD(34+)-enriched human cord blood cells. RT-PCR analysis of 22 different cytokines or cytokine receptor mRNAs showed an almost identical expression pattern in the two stromal cell lines compared to primary human Dexter-type stroma. Since stromal feeder lines employed in long-term cultures usually are irradiated and grown in media containing corticosteroids, we analyzed the impact of irradiation and dexamethasone on cytokine production in the two cell lines by RT-PCR, Northern blot analysis, bioassays, and RIAs. By RT-PCR analysis, constitutive mRNA expression of c-kit, G-CSF, GM-CSF, IL-1 beta, IL-6, IL-7, IL-8, IL-11, Kit ligand (KL), LIF, M-CSF, MIP-1 alpha, TGF-beta, and TNF-alpha was demonstrated in both cell lines, with L87/4 a more potent cytokine producer than L88/5. Northern blot data showed an increase in mRNA levels for GM-CSF, IL-1 beta, and LIF by irradiation and IL-1 alpha treatment in both cell lines. IL-1 alpha-induced GM-CSF, IL-1 beta, IL-6, IL-11, and LIF mRNA levels were reduced by the addition of dexamethasone, whereas dexamethasone had no influence on the amounts of IL-1 alpha-induced G-CSF mRNA. L87/4 and, to a lower extent, L88/5 cells showed dexamethasone-dependent increases in KL mRNA, while KL mRNA levels were not stimulated by IL-1 alpha.

Tetrahydro-6-biopterin is associated with tetrahydro-7-biopterin in primary murine mast cells.

Murine bone marrow-derived mast cells proliferate in response to interleukin 3. In addition to 6-biopterin, 7-biopterin was identified in these cells by HPLC analysis of iodine oxidized extracts and by alkaline permanganate oxidation to the 6- and 7-carboxylic acids. 7-Biopterin comprised 31.9 (+/- 7.7)% of the total biopterin. It was absent in cells which were grown with of L-p-chlorophenylalanine, an inhibitor of tryptophan 5-mono-oxygenase. Both 6- and 7-biopterin were present in the cell as their tetrahydro forms. From these data we conclude that 7-biopterin, in contrast to e.g. brain tissue, regularly occurs as a normal metabolite in primary mast cells and that it is generated during hydroxylation of tryptophan.

Induction of leukotriene production by bleomycin and asparaginase in mast cells in vitro and in patients in vivo.

Bleomycin and asparaginase are widely used antineoplastic agents which may induce allergic or inflammatory side-effects. Mast cells are implicated as effector cells in allergic and inflammatory responses. The aim of this study was to establish whether bleomycin or asparaginase modulate leukotriene production in vitro and in vivo. Leukotriene C4 (LTC4) production by murine bone marrow-derived mast cells (BMMC) was determined by radioimmunoassay (RIA). Leukotriene production in patients was assessed by determining leukotriene E4 and N-acetyl-leukotriene E4 in urine by means of combined HPLC and RIA. Bleomycin induced an up to 2.1-fold increase in LTC4 production both in unstimulated and in calcium ionophore-stimulated mast cells. In 3 of 7 patients treated with bleomycin, a greater than 2-fold increase in endogenous leukotriene production was observed. This effect was associated with febrile responses and was most pronounced in a patient who developed an Adult Respiratory Distress Syndrome (ARDS). Asparaginase increased leukotriene production up to 10-fold in stimulated but not in unstimulated BMMC. In a patient who developed an anaphylactic reaction after treatment with asparaginase, a pronounced increase in urinary leukotriene concentration was observed. In contrast to bleomycin or asparaginase, a number of other cytostatic agents did not significantly change leukotriene production by BMMC. Our data indicate that some of the inflammatory and allergic side-effects of bleomycin and asparaginase could be mediated by leukotrienes, a possible source of which may be mast cells.

Evaluation of Fc-receptor positive (FcR+) and negative (FcR-) monocyte subsets in sepsis.

The monocyte/macrophage (Mphi is central in the regulation of the immune response in states of trauma and sepsis. Because monocyte subsets, characterized by expression of the Fc-receptor (FcR), were shown to play distinct immunologic roles in trauma, it was the objective of this study to assess insights into the functional role of FcR positive (FcR+) and negative (FcR-) subclasses in surgical sepsis. In a prospective study, peripheral blood Mphi from 20 septic patients and 10 healthy volunteers were evaluated on consecutive days after the onset of sepsis. FcR+/- subsets were separated by rosetting with antibody-coated human erythrocytes. Receptor expression and synthesis of proinflammatory cytokines were used to evaluate the functional role of these cells. We demonstrated a significant monocytosis (350%; p<.01) and suppression of human lymphocyte antigen (HLA-DR) expression (35%; p<.05). Synthesis of Interleukin-1beta (IL-1beta; e.g., Day 1: 230+/-30 pg/mL) and Interleukin-6 (IL-6; e.g., Day 1: 1920+/-350 U/mL) were significantly higher (p<.05) in FcR+ subsets than in controls (IL-1beta: 100+/-5 pg/mL; IL-6: 353+/-75 U/mL). Tumor necrosis factor-alpha (TNF-alpha) was elevated in FcR+ monocytes but did not reach a significant value. Interleukin-8 (IL-8) synthesis showed only on Day 1 and in controls significant differences in FcR+ and FcR- cells (Day1: FcR-: 19.6+/-4.1 nM; FcR+: 9+/-4.3 nM). Sepsis results in a significant shift toward FcR+ monocytes. This cell population is characterized by high proinflammatory cytokine synthesis. The extent of this shift seems to identify a group of high risk septic patients that might benefit from immunomodulatory therapy.

Cellular and molecular mechanisms of TNF protection in septic peritonitis.

Requirement for endogenous TNF for survival of experimental septic peritonitis has been demonstrated in a mouse model of cecal ligation and puncture (CLP). Induction of endogenous TNF production before CLP or administration of TNF before or after CLP confered protection from death. Interaction of TNF with the p55TNF receptor, formation of fibrin deposits, and granulocyte function was necessary to survive CLP. The mast cell seems to be an important cell type to provide the TNF required for protection in this model.

Functional analysis of monocyte activity through synthesis patterns of proinflammatory cytokines and neopterin in patients in surgical intensive care.

This study was designed to further differentiate monocyte behavior in critically ill patients with operative or accidental trauma. The patient population studied consisted of 39 patients (17 patients undergoing elective surgery [ES], seven patients with major multiple injuries [MI], and 15 patients in an acute septic state [S]). Immunologic parameters assessed included monocyte phenotyping with the monoclonal antibody LeuM3, measurement of the cytokines interleukin (IL)-1, IL-6, and IL-8 in lipopolysaccharide-stimulated in vitro cultures of mononuclear leukocytes (PBMCs), and determination of neopterin in gamma-interferon-stimulated in vitro cultures and corresponding serum samples. Serum neopterin levels were very high in S patients (89.0 nmol/L; p less than 0.05) compared with control values (4.6 nmol/L), with a rise to 16.4 nmol/L in ES patients on day 7 and 13.4 nmol/L in MI patients on day 7. The concentrations of gamma-interferon-induced neopterin in the supernatants of the PBMC cultures were elevated in all patient groups. Severe impairment of IL-1 synthesis was seen in MI and S patients. IL-8 synthesis (818 +/- 150 units/ml, control value) was also suppressed (p less than 0.05) in MI patients; the values were 135 +/- 65 units/ml on day 1,231 +/- 110 units/ml on day 3,347 +/- 131 units/ml on day 7, and 355 +/- 107 units/ml in S patients. The kinetic patterns of synthesis were comparable for IL-1 and IL-8 in all patient groups. Lipopolysaccharide-induced IL-6 synthesis (9.4 +/- 1.5 x 10(3) units/ml, control value) was significantly elevated in the PBMC cultures of all patient groups, with the exception of the early phase after accidental trauma. Maximum amounts of IL-6 synthesis after surgery were 19.6 +/- 7 x 10(3) units/ml in S patients and 19.0 +/- 2.2 x 10(3) units/ml in ES patients. These results demonstrate (1) the impairment of the functional capacity of circulating monocytes and (2) that the degree of functional impairment is proportional to the severity of the injury.

Regulation of acute phase response after cardiopulmonary bypass by immunomodulation.

The object of this prospective, randomized trial was to study the dysregulation effects of cardiopulmonary bypass on the synthesis pattern of interleukin-1, tumor necrosis factor, and interleukin-6, which have been identified as the key mediators of acute phase response. In addition, the counterregulation achieved by administration of indomethacin, which blocks the downregulating mediator prostaglandin E2, or indomethacin combined with thymopentin, which enhances T-lymphocytic reactivity, was investigated. Sixty patients who had undergone open heart operations were included in the study. These patients were divided into three groups: group A (n = 20) received both indomethacin and thymopentin, and group C (n = 20) served as control. In control patients interleukin-1 and tumor necrosis factor synthesis were suppressed postoperatively. This effect was significantly counteracted by indomethacin with no further improvement by adding thymopentin. Interleukin-6 synthesis increased in all groups. Although indomethacin treatment alone had little effect on this phenomenon, additional administration of thymopentin significantly reduced elevated interleukin-6 synthesis. Corresponding differences in clinical outcome could not be detected due to small patient numbers. This study was, however, able to demonstrate that an immunomodulatory therapy can influence alterations in immune mechanisms after cardiopulmonary bypass.

Alterations of cell-mediated immune response following cardiac surgery.

Nosocomial infections in patients following cardiac surgery are frequently associated with opportunistic microorganisms indicating a dysregulation of cell-mediated immune response. The objective of this prospective randomized trial, therefore, was to investigate the mechanisms of dysregulation and the counterregulatory effects of immunomodulation. Twenty patients underwent conventional postoperative therapy, another 20 patients received indomethacin, which inhibits synthesis of the down-regulating mediator prostaglandin E2, and a further 20 patients were given thymopentin in addition to indomethacin, thereby augmenting activation and differentiation of the T-lymphocytes. The immunologic parameters studied included T-lymphocytes and monocytes as well as interleucin (IL)-1 and IL-6 synthesis by monocytes, and IL-2 and IL-6 synthesis by T-lymphocytes. Following cardiac surgery a significant, persistent reduction of T-lymphocytes and IL-2 synthesis as well as significant monocytosis could be observed. Indomethacin treatment resulted in a normalization of the cellular imbalance at the end of the first postoperative week, but IL-2 synthesis remained significantly reduced during the entire observation period. Conversely, with combined indomethacin and thymopentin treatment restoration of cellular distribution as well as protection of IL-2 synthesis could be achieved. These results indicate a quantitative and functional impairment of the forward regulation of cell-mediated immunity. It was shown for the first time that combined indomethacin and thymopentin treatment could successfully counteract these immunomechanistic alterations.

An imbalance in T-helper cell subsets alters immune response after cardiac surgery.

Growing evidence indicates that cell-mediated immunity is altered after cardiac surgery with cardiopulmonary bypass (CPB). The objective of this prospective randomized study was to investigate (1) if an imbalance in T-helper cell (TH) subsets, i.e. TH1/TH2, may be responsible for these alterations and (2) if they can be counteracted. Twenty patients formed control group A. Twenty group B patients received indomethacin and thymopentin for immunomodulation. In vitro tests included measurements of TH, interleukin (IL)-2 as a cytokine primarily produced by TH1 cells, and IL-6 as a cytokine primarily produced by TH2. Delayed-type hypersensitivity (DTH) skin response and specific antibody (AB) production were used as in vivo tests for TH1- and TH2-induced immune response, respectively. Postoperatively, group A patients showed a persistent, significant reduction of TH, IL-2 synthesis and DTH skin response as compared to baseline values, while IL-6 synthesis remained unaltered and AB production increased (P < 0.05). In group B patients no change in TH, IL-2 and IL-6 synthesis, or DTH skin response was observed (P < 0.05 vs A). Postoperative AB production increased significantly in group B. These results indicate a significant suppression of TH1-induced cell-mediated immune response following CPB, while TH2-induced response remains normal. A normal TH2 response may be helpful for recovery following cardiac surgery by cleaning the body of the byproducts of CPB. A suppression of TH1 response may gain clinical significance whenever a postoperative infection requires this response, but can be effectively counteracted by immunomodulatory intervention with indomethacin and thymopentin.

Proliferation and maturation of human bone marrow cells in infectious diseases.

In 6 patients with various types of infectious disease an extended study of proliferation and maturation of erythropoiesis and granulocytopoiesis was performed. By means of quantitative 14C-autoradiography DNA synthesis time and labeling index were determined in every morphologically defined cell compartment of both lineages. With these parameters and the relative frequency of cells in the various compartments cell cycle times, relative cell production rates and maturation indices were determined. A general labeling index reduction and prolongation of DNA synthesis time was observed which was statistically significant in the majority of compartments. As a consequence, cell cycle times were prolonged throughout, the deviation from normal increasing with advancing maturation in both lineages. Relative cell production was normal in myelocytes, but elevated in myeloblasts and promyelocytes. On the other hand, proerythroblasts and basophilic erythroblasts showed normal relative cell production rates, while a significantly reduced value was found in polychromatic erythroblasts. The maturation index in both lineages was reduced by roughly 50%. Since cell cycle times were generally prolonged, the most significant deviations from normal being present in the latest proliferative compartments, the low maturation indices are discussed in the light of ineffective erythro- and granulocytopoiesis. Premature cell death in the bone marrow is suggested to be a significant factor in particular cases of infectious disease.