Identification of cyclophilin as a proinflammatory secretory product of lipopolysaccharide-activated macrophages.

We have isolated an 18-kDa peptide (designated sp18, for 18-kDa secreted protein) from the conditioned medium of lipopolysaccharide-stimulated RAW 264.7 murine macrophages. Purified sp18 had in vivo inflammatory activity and in vitro chemotactic activity for human peripheral blood polymorphonuclear leukocytes and monocytes. Surprisingly, N-terminal sequencing and tryptic mapping studies revealed that sp18 and cyclophilin, an intracellular protein that binds the immunosuppressive drug cyclosporin A, are highly homologous. The in vitro chemotactic activity of sp18 on monocytes was blocked by cyclosporin A but not by cyclosporin H, a structural analog of cyclosporin A that does not bind cyclophilin. Like purified porcine cyclophilin, mouse sp18 exhibited peptidyl-prolyl cis-trans isomerase activity. Medium conditioned by lipopolysaccharide-stimulated resident peritoneal exudate macrophages isolated from C57BL/6 mice contained substantially higher levels of sp18/cyclophilin than medium conditioned by nonstimulated macrophages. The observation that sp18/cyclophilin exhibits proinflammatory activity and is secreted by macrophages in response to endotoxin suggests that this protein may function as a cytokine, and invites the hypothesis that the immunosuppressive action of cyclosporin A results in part from interaction with an extracellular form of cyclophilin released as a mediator of immune and inflammatory functions.     

Interferon decreases the growth inhibition of Mycobacterium avium-intracellulare complex by fresh human monocytes but not by culture-derived macrophages

Using a rapid radiolabel assay, monocytes derived from the peripheral blood of normal donors were found to kill 40%-92% of inoculated Mycobacterium avium-intracellulare complex (MAC), an opportunistic pathogen commonly found in AIDS patients. However, bactericidal activity was significantly lower in 4-day culture-derived macrophages compared with matched monocyte cultures. The addition of interferon-gamma (IFN-gamma) to monocytes was found to inhibit the bactericidal activity of fresh monocytes. The number of bacteria recovered from fresh monocytes exposed to IFN-gamma was significantly higher than that in control cultures with MAC alone, suggesting that intracellular MAC growth could be stimulated by IFN-gamma. This enhancement of MAC survival and growth by IFN-gamma was not observed when culture-derived macrophages were used. Similar results were obtained with IFN-alpha/A2. These results indicate, therefore, that the innate efficiency of mycobacterial killing by monocytes can be down-regulated by IFN, but macrophages are not significantly affected.     

Killing of Plasmodium falciparum by human monocyte–derived macrophages

Freshly isolated human peripheral blood monocytes inhibited the growth of blood-stage asexual Plasmodium falciparum parasites in vitro. The monocytes contained intracellular parasite pigment and a few whole parasites, but the remaining parasites reinvaded fresh red cells successfully and were morphologically normal. Anti-parasitic activity of these macrophages was not significantly enhanced by treatment with recombinant tumour necrosis factor alpha, recombinant gamma-interferon or lymphoblastoid alpha-interferon. Catalase had no effect on this parasite inhibition, suggesting a hydrogen peroxide independent mechanism. Anti-parasitic activity was, however, enhanced by prior maturation of the monocytes. Monocytes matured for 6 days caused 100% killing of parasites. In contrast to identical concentrations of freshly isolated monocytes the parasites incubated with these matured macrophages showed intraerythrocytic death similar to the crisis forms seen in vivo. gamma-interferon present either during the assay or as a pretreatment had no significant enhancing effect on the killing, although cytotoxicity to tumour cell lines was enhanced. Conditioned medium from macrophages showed only moderate parasite inhibition.     

Telomerase activity in normal and malignant hematopoietic cells.

Bone marrow and peripheral blood leukocytes from 19 leukemia patients were found to contain telomerase activity detectable by a PCR-based assay. Telomerase was also detectable in nonmalignant bone marrow and peripheral blood leukocytes from normal donors, including fractions enriched for granulocytes, T lymphocytes, and monocytes/B cells. Semiquantitative comparison revealed considerable overlap between telomerase activities in samples from normal subjects and leukemia patients, confounding evaluation of the role of telomerase in this disease. These data indicate that human telomerase is not restricted to immortal cells and suggest that the somatic expression of this enzyme may be more widespread than was previously inferred from the decline of human telomeres.     

Respiratory syncytial virus infection of human cord and adult blood monocytes and alveolar macrophages

We studied the permissiveness of human leukocytes, blood monocytes, alveolar macrophages, and cord blood monocytes to infection with respiratory syncytial virus (RSV). Specific immunofluorescence was used to determine the percentage of infected leukocytes. The results indicated that monocytes were the most susceptible human leukocyte to in vitro infection with RSV. Polymorphonuclear leukocytes demonstrated no specific fluorescent staining after 24 h of exposure to RSV, whereas peripheral blood nonadherent mononuclear cells demonstrated a low percentage of positive cells, with a mean of 6 +/- 1% SE. In contrast, 37 +/- 5% of monocytes expressed RSV antigen after viral exposure. Exposure of monocytes to lipopolysaccharide (LPS) for 1 h prior to RSV increased the percentage of infected cells to 48 +/- 6% and stimulated their secretion of prostaglandin E2 (PGE2) and alpha tumor necrosis factor (TNF). Intrinsic mononuclear phagocytic factors influencing the permissiveness to RSV were studied by determining infection of adult and cord blood and alveolar mononuclear phagocytes (MP). Alveolar and blood MP simultaneously isolated from adult donors were similarly infected by RSV, which varied with the viral dose. Cord blood MP were more susceptible to RSV infection than were adult MP, 58 +/- 9% infected versus 37 +/- 5%, respectively (p less than 0.05). Treatment with LPS for 1 h prior to RSV exposure did not increase infection of cord blood MP as seen with adult blood MP. However, LPS can induce human monocytes to secrete cytokines with antiviral activity, and our results indicate that both gamma interferon and TNF, independently or in combination, prevented infection of monocytes in a dose-dependent manner.     

Dyscoordinate expression of tumor necrosis factor-alpha by human blood monocytes and alveolar macrophages

Previous studies have shown that human alveolar macrophages produce less interleukin-1 (IL-1) in response to lipopolysaccharide (LPS) than do their precursors, blood monocytes. The purpose of this study was to compare the capacities of alveolar macrophages and blood monocytes to synthesize tumor necrosis factor (TNF) in response to LPS. Alveolar macrophages were obtained by bronchoalveolar lavage of healthy nonsmoking subjects, and blood monocytes were obtained by adherence of mononuclear cells to plastic. TNF activity was measured in supernatants and cell lysates as cytotoxicity to L929 fibroblasts (uptake of neutral red at 570 nm). TNF activity of alveolar macrophages stimulated at 10(6) cells/ml with LPS (10 micrograms/ml) for 16 h was 596 +/- 367, and of blood monocytes it was 60 +/- 84 U/ml (mean +/- SD, p less than 0.005). At no concentration of LPS and at no period of stimulation did alveolar macrophages express less TNF activity than did blood monocytes. In concurrent experiments, supernatants of LPS-stimulated alveolar macrophages contained less IL-1 activity than did blood monocytes. Lysates of both cell types contained less than 20% of total TNF activity. The TNF activity of LPS-stimulated alveolar macrophages was neutralized greater than 99% by monoclonal antibody to TNF-alpha; control monoclonal antibody OKT3 had no effect. Next, alveolar macrophages and blood monocytes were biosynthetically labeled with [3H]leucine during incubation with LPS; supernatants were immunoprecipitated with anti-TNF, and precipitates were electrophoresed on polyacrylamide gels. Autoradiographs indicated that immunoreactive TNF was produced by both blood monocytes and alveolar macrophages and that the relative molecular weights were identical (17,000).(ABSTRACT TRUNCATED AT 250 WORDS)     

Anticomplement receptor activity in the serum of patients with primary biliary cirrhosis.

Patients with primary biliary cirrhosis have a defect in the receptor mediated clearance of complement coated erythrocytes by fixed macrophages of the reticuloendothelial system. To investigate the probable mechanism of this defect peripheral blood monocytes were isolated from nine patients with primary biliary cirrhosis and seven control subjects and the ability of these cells to form rosettes with complement coated, IgM-sensitised sheep erythrocytes was assessed. Primary biliary cirrhosis peripheral blood monocytes formed rosettes to the same extent as control peripheral blood monocytes (71.0 +/- 7.1% [SEM] versus 73.3 +/- 4.3%) suggesting normal complement receptor function of primary biliary cirrhosis peripheral blood monocytes. When primary biliary cirrhosis or control peripheral blood monocytes were preincubated with primary biliary cirrhosis serum, however, the per cent of peripheral blood monocytes that formed rosettes was decreased: 2.4 +/- 0.8 and 3.1 +/- 1.3 fold respectively. To study this phenomenon further, fractions containing IgG or IgM synthesised by cultures of control or primary biliary cirrhosis lymphocytes were prepared. Rosette formation was not affected by exposure to fractions containing control or primary biliary cirrhosis IgG or control IgM, but was markedly inhibited (6.0 +/- 4.8 fold) by exposure to fractions containing primary biliary cirrhosis IgM. Similar results were obtained when freshly isolated peripheral blood monocytes or peripheral blood monocytes that had been cultured for 7-10 days--that is, macrophages, were used. Assuming that one can draw inferences concerning the status of fixed macrophages from data obtained using peripheral blood monocytes, the results of this study suggest that the complement specific defect in reticuloendothelial system clearance function in primary biliary cirrhosis is not caused by abnormality in the functional status of complement receptors on fixed macrophages but rather by a factor present in the serum of patients with primary biliary cirrhosis that has the capacity to inhibit the adherence of complement coated erythrocytes to complement receptors present on the surface of fixed macrophages. This serum factor does not appear to be a complement component but rather a product of peripheral blood mononuclear cells, other than IgG.     

Discrimination of resident and infiltrated alveolar macrophages by flow cytometry in influenza A virus-infected mice

Laser flow cytometric analysis was used in conjunction with in vivo labeling with the lipophilic fluorescent dye DiIC18(5)-DS to discriminate resident alveolar macrophages from newly infiltrating monocytes/macrophages in mice with and without pulmonary influenza A virus infection. Leukocytes in bronchoalveolar lavage (BAL) and peripheral blood were analyzed by 2-color flow cytometry as a function of time following intravenous injection of DiIC18(5)-DS. At 4 hours, dye-positive leukocytes were present in both BAL and blood of normal mice, indicating that DiIC18(5)-DS rapidly crossed the pulmonary endothelial-epithelial barrier. At 4 days after dye injection, 98% of BAL cells were DiIC18(5)-DS positive, and almost all of these were monocytes/macrophages based on labeling with fluorescein isothiocyanate (FITC)-conjugated antibody to the Mac-3 marker. Only 3.2% +/- 0.3% of peripheral blood monocytes (approximately 0.16% of total peripheral blood leukocytes) were DiIC18(5)-DS positive at 6 days after injection, whereas > 95% of BAL leukocytes were strongly dye-positive on days 6 to 28. When DiIC18(5)-DS was injected in mice 6 days prior to intranasal challenge with influenza A, flow cytometry indicated that 57.8% 5.6% and 60.7% +/- 8.5% of macrophages/monocytes in BAL were newly infiltrated (i.e., DiIC18(5)-DS negative, Mac-3 positive) at 4 and 7 days, respectively, post viral infection. The discrimination of subpopulations of resident and newly recruited macrophages in BAL should facilitate future mechanistic studies on pulmonary infection and inflammatory lung injury.     

Blood monocytes and tumor-associated macrophages in human cancer: differences in activation levels

This study was performed to investigate functional properties of mononuclear phagocytes isolated from ascitic fluid in patients with peritoneal carcinomatosis (PC), and potential immunomodulatory effects of soluble factors produced or induced by human metastatic malignant cells. Phagocytic activity and nitric oxide production of peripheral blood monocytes (PBMo) and tumor-associated macrophages (TAM) or peritoneal macrophages (PEM) were synchronously examined in cancer patients and control individuals. Our results showed that contrary to peripheral blood monocytes, where phagocytic activity was not altered, TAM had impaired phagocytic activity. Moreover, dilutions of crude supernatant from short-term cultures of the peritoneal cells obtained from ascitic fluid of patient with PC, cause a significant, dose dependent inhibition of control PBMo and PEM phagocytosis, comparable to those in TAM, indicating that a soluble factor(s) plays a prominent role in this alteration. Next, we investigated the potential of cancer patients mononuclear phagocytes to produce nitric oxide (NO). It was found that TAM produce fourfold lower levels of NO than PEM from control subject, whereas monocytes produce NO at levels comparable to those of corresponding controls. These data support the hypothesis that depressed TAM function may contribute to the mechanisms of tumor escape from immune destruction.     

Effects of reagent and cell-generated hydrogen peroxide on the properties of low density lipoprotein.

Low density lipoprotein (LDL) isolated from human plasma anticoagulated with EDTA (EDTA/LDL) was 4-fold more resistant to oxidation by reagent H2O2, as assayed by the thiobarbituric acid (TBA) assay, than LDL prepared from plasma anticoagulated with citrate (CDP/LDL). The LDLs required 1-3 mM H2O2 for maximal oxidation by this assay, and ED50S were 1.7 X 10(-3) M for EDTA/LDL and 4.5 X 10(-4) M for CDP/LDL. Oxidation was enhanced 2.3-fold by Cu2+ ions. Rabbit endothelial cell line monolayers released two orders of magnitude less H2O2 than was required to oxidize LDL and failed to induce TBA reactivity in either EDTA/LDL or CDP/LDL after a 24-hr coincubation. However, this LDL was subsequently degraded by mouse macrophages more rapidly than untreated LDL. Freshly isolated human monocytes (2 X 10(6) cells per ml), with or without phorbol myristate acetate (100 ng/ml) to trigger the respiratory burst, did not oxidize LDL in the TBA assay, despite producing large amounts of reactive oxygen intermediates. EDTA/LDL, CDP/LDL, and acetoacetylated LDL failed to trigger H2O2 release from human monocytes or macrophages. These results separate oxidation of LDL as measured by TBA assay from the modification of LDL by rabbit aortic endothelial cell line that leads to its subsequent enhanced degradation by macrophages.     

Smoking and interleukin-1 activity released from human alveolar macrophages in healthy subjects

To evaluate the activation of alveolar macrophages from smoking, we studied interleukin-1 (IL-1) activity released from alveolar macrophages in eight healthy smokers, compared to 12 healthy nonsmokers. We used 24-hour culture supernatants containing IL-1 of bronchoalveolar lavage fluid (BALF) macrophages/blood monocytes with or without LPS stimulation. Using C3H/HeJ thymocyte PHA costimulation assay, we found that IL-1 activity released from LPS stimulated BALF macrophages was significantly higher in smokers (2.39 +/- 0.33 U/ml) than in nonsmokers (1.47 +/- 0.19 U/ml, p less than 0.05). We also detected IL-1 inhibitory activity in supernatants by using IL-1 inhibitory assay. The inhibitory activity was higher in nonsmokers than in smokers especially under LPS stimulation. The presence of inhibitory factors other than prostaglandin-E2 was suggested from the differential response to the addition of indomethacin into cultures from nonstimulated and LPS-stimulated supernatants of BALF macrophages.     

Cooperation between accessory cells and T lymphocytes in patients with tuberculous pleurisy

We studied interleukin 1 (IL-1) activity of pleural fluid macrophages and peripheral blood monocytes obtained from ten patients with tuberculous pleurisy and ten patients with malignant pleurisy, using purified protein derivative (PPD) as a stimulating agent. Tuberculous pleural fluid macrophages and peripheral blood monocytes tended to produce higher IL-1 activity than malignant pleural fluid macrophages and blood monocytes and showed significantly more IL-1 activity than healthy control monocytes. However, no significant difference in IL-1 activity was observed between tuberculous pleural macrophages and blood monocytes. With the cooperation of these accessory cells, pleural fluid T lymphocytes in patients with tuberculous pleurisy showed a significant level of interleukin 2 (IL-2) activity in the presence of PPD. Tuberculous pleural fluid macrophages promoted greater IL-2 production than blood monocytes from either tuberculous pleural fluid or blood T lymphocytes despite relative equivalence in measured IL-1 production. Combination of tuberculous pleural fluid macrophages and pleural fluid T lymphocytes was the most effective for increasing IL-2 activity when compared with other combinations. These results suggest that tuberculous pleural fluid macrophages and T lymphocytes may contribute to the immunopathogenesis of tuberculosis at a local site of disease.     

Acid phosphatase activity in mononuclear phagocytes and the U937 cell line: monocyte-derived macrophages express tartrate-resistant acid phosphatase

Tartrate-resistant acid phosphatase (TRAcP) is used as a marker for osteoclasts, which are believed to be derived from phagocytic cells or phagocyte stem cell precursors. To further investigate the relationship between monocytic phagocytes and osteoclasts, acid phosphatase (AcP) activity was measured by three different techniques in human peripheral blood monocytes, monocyte-derived macrophages, and the U937 cell line. We found that cytochemistry and gel electrophoresis led to similar results, but that the colorimetric assay was inconsistent. Normal human peripheral monocytes expressed both tartrate-sensitive and -resistant AcP. In culture these cells formed polykaryons and expressed TRAcP activity that was further identified as an isoenzyme associated with bone tissue. In contrast, the U937 cells did not express TRAcP activity as measured by gel electrophoresis. Both U937 cells and monocytes possess material that interferes with interpretation of the colorimetric assay of AcP. The presence of TRAcP in monocyte-derived macrophages further supports the relationship between phagocytic cells and bone osteoclasts.     

Human monocytes are severely impaired in base and DNA double-strand break repair that renders them vulnerable to oxidative stress

Monocytes are key players in the immune system. Crossing the blood barrier, they infiltrate tissues and differentiate into (i) macrophages that fight off pathogens and (ii) dendritic cells (DCs) that activate the immune response. A hallmark of monocyte/macrophage activation is the generation of reactive oxygen species (ROS) as a defense against invading microorganisms. How monocytes, macrophages, and DCs in particular respond to ROS is largely unknown. Here we studied the sensitivity of primary human monocytes isolated from peripheral blood and compared them with macrophages and DCs derived from them by cytokine maturation following DNA damage induced by ROS. We show that monocytes are hypersensitive to ROS, undergoing excessive apoptosis. These cells exhibited a high yield of ROS-induced DNA single- and double-strand breaks and activation of the ATR-Chk1-ATM-Chk2-p53 pathway that led to Fas and caspase-8, -3, and -7 activation, whereas macrophages and DCs derived from them were protected. Monocytes are also hypersensitive to ionizing radiation and oxidized low-density lipoprotein. The remarkable sensitivity of monocytes to oxidative stress is caused by a lack of expression of the DNA repair proteins XRCC1, ligase IIIα, poly(ADP-ribose) polymerase-1, and catalytic subunit of DNA-dependent protein kinase (DNA-PK(cs)), causing a severe DNA repair defect that impacts base excision repair and double-strand break repair by nonhomologous end-joining. During maturation of monocytes into macrophages and DCs triggered by the cytokines GM-CSF and IL-4, these proteins become up-regulated, making macrophages and DCs repair-competent and ROS-resistant. We propose that impaired DNA repair in monocytes plays a role in the regulation of the monocyte/macrophage/DC system following ROS exposure.     

Enhanced lipoprotein lipase secretion and foam cell formation by macrophages of patients with growth hormone deficiency: possible contribution to increased risk of atherogenesis?

GH deficiency is associated with increased prevalence of atherosclerosis, and recent data indicate a proatherogenic role for macrophage lipoprotein lipase (LPL) in the arterial wall. In this pilot study, we determined LPL expression and foam cell formation in monocyte-derived macrophages of 12 control subjects and nine patients with GH deficiency without GH replacement therapy. LPL mRNA levels, mass, and activity were increased in macrophages of patients with GH deficiency. In these subjects, macrophage LPL activity correlated with body mass index and fat mass. Incubation of patient macrophages with IGF-I for 24 h or differentiation of monocytes isolated from GH-deficient patients into macrophages in the presence of this growth factor decreased the amount of LPL mass. Compared with control cells, macrophages derived from GH-deficient patients took up and stored increased amounts of proatherogenic lipoproteins and were more easily converted to foam cells. In the supernatants of these cells, increased levels of free fatty acids and TNFalpha were also documented. These results demonstrate that macrophages of patients with GH deficiency secrete increased amounts of proatherogenic cytokines and are more susceptible to foam cell formation. These alterations may contribute to the increased cardiovascular risk in patients with GH deficiency.     

Human adipose tissue macrophages are of an anti-inflammatory phenotype but capable of excessive pro-inflammatory mediator production

OBJECTIVE: Obesity is associated with a chronic low-grade inflammation and an increased abundance of macrophages in adipose tissue. Adipose tissue macrophages (ATMs) are assumed to interfere with adipocyte function leading to insulin resistance, thereby contributing to the pathogenesis of type 2 diabetes mellitus. Macrophages exist in separate types of differentiation, but the nature of ATMs is largely unknown. DESIGN AND MEASUREMENTS: Stromal vascular cells (SVCs) and ATMs were isolated from human adipose tissues from different locations. We characterized ATMs phenotypically and functionally by flow cytometry, endocytosis assay and determination of secreted cytokines. For comparison, we used macrophages of the 'classical' (M1) and the 'alternative', anti-inflammatory (M2) type differentiated in vitro from peripheral blood monocytes. RESULTS: Like prototypic M2 macrophages, ATMs expressed considerable amounts of mannose receptor, haemoglobin scavenger receptor CD163 and integrin alphavbeta5. The number of cells expressing these molecules correlated significantly with the donors' body mass indices (BMIs). Notably, SVCs positive for the common monocyte/macrophage marker CD14 contained a considerable fraction of blood monocytes, the abundance of which did not correlate with the BMIs, pointing to the requirement of the surface markers identified here for the identification of ATMs. ATMs showed endocytic activities similar to M2 macrophages and accordingly secreted high amounts of IL-10 and IL-1 receptor antagonist. However, basal and induced secretion of pro-inflammatory mediators TNF-alpha, IL-6, IL-1, MCP-1 and MIP-1alpha was even higher in ATMs than in pro-inflammatory M1 macrophages. CONCLUSION: ATMs comprise a particular macrophage type that is M2-like by surface marker expression, but they are competent to produce extensive amounts of inflammatory cytokines, which could considerably contribute to the development of insulin resistance.     

Vascular endothelium as a regulator of granulopoiesis: production of colony-stimulating activity by cultured human endothelial cells

Colony-stimulating activity is a regulatory factor(s) that promotes differentiation of hemopoietic stem cells to mature granulocytes and macrophages; in man it has been found that blood monocytes, lymphocytes, and tissue macrophages produce it. In an effort to identify other potenitally physiologic tissue sources of colony- stimulating activity, we have studied the capacity of primary cultures of human vascular endothelial cells to produce colony-stimulating activity. Medium conditioned by incubation with endothelial cultures contained activity that promoted granulocyte-macrophage colony formation of nonadherent human and murine marrow cells. Exposure of endothelial cultures to 0.1-5.0 microgram/ml S. typhosa endotoxin for 6- 72 hr enhanced colony-stimulating activity production. Similarly, incubation of endothelial cells with lysates of human blood granulocytes, or cocultivation with intact granulocytes, resulted in increased colony-stimulating activity levels. In 7-14 day cultures, freshly isolated endothelial cells, incorporated into agar underlayers, consistently stimulated more colony formation by nonadherent human marrow cells than comparable numbers of blood monocytes. These data indicate that: (1) cultured human endothelial cells are a potent source of colony-stimulating activity; (2) they respond to endotoxin and granulocytes and their contents by producing increased amounts of CSA; and (3) they produce morea colony-stimulating activity, than human blood monocytes under standardized conditions in vitro. These observations suggest that the vascular endothelium may play a role in the physiologic regulation of granulopoiesis.     

Production of an interleukin-1 inhibitory factor by human alveolar macrophages from normals and allergic asthmatic patients

In order to study the possible role of alveolar macrophages (AMs) in the development of local immune responses, we compared interleukin-1 (IL-1) production by peripheral blood monocytes and AMs from 17 allergic asthmatics and 32 controls. When stimulated by lipopolysaccharide, alveolar macrophages and blood monocytes from controls released IL-1 (127 +/- 74.6 and 178.8 +/- 120 IL-1 units/ml, respectively) in the same amounts as AMs and blood monocytes from allergic asthmatics (148 +/- 47.5 and 160.5 +/- 78.3 IL-1 units/ml, respectively). After stimulation by anti-IgE or the specific allergen, asthmatic blood monocytes released IL-1-like activity (71.8 +/- 46.4 and 45.4 +/- 25.9 IL-1 units/ml, respectively). In contrast, asthmatic AM supernatants contained no detectable IL-1-like activity after stimulation by allergen or anti-IgE. The same pattern was observed with monocytes and AMs from controls after passive cell sensitization with 20% of IgE-rich serum. In a second step, the effect of supernatants of IgE-dependent stimulated AMs was tested on thymocyte proliferation induced by a purified IL-1, permitting the demonstration of an IL-1 inhibitory factor released by the AMs while these supernatants didn't modify the IL-2-dependent proliferation of a CTL-L line. The use of indomethacin and assessment of PGE2 levels in AM supernatants made it possible to discard the role of prostaglandins in this inhibitory effect. Moreover this activity, which is resistant to heat and trypsin treatment, has a molecular mass between 40 and 50 kD and did not correspond to serum proteases, alpha-1-antiproteinase, and arginase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of interleukin 1, macrophage colony-stimulating factor, and factor increasing monocytopoiesis on the production of leukocytes in mice.

The present study was designed to establish that the factor increasing monocytopoiesis (FIM) is a unique factor that differs from interleukin 1 (IL-1) and macrophage colony-stimulating factor (M-CSF) in its effect on the production of granulocytes, lymphocytes, and monocytes in C3H/HeJ mice, which are unresponsive to lipopolysaccharide. [3H]thymidine, together with the cytokine under study, was used as a marker for newly formed cells. The number of each category of labeled leukocytes in the circulation was calculated from the number of leukocytes per microliter of blood, differential counts of the leukocytes, and their labeling indices, as determined by autoradiography. To compare the effect of the various cytokines on the production of leukocytes, the area under the curve (AUC) of the number of each category of leukocytes over a period of 96 h has been calculated. The results show that IL-1 causes, within 2 h, an increase in the number of circulating granulocytes, most probably by recruitment of these cells from the storage pool in the bone marrow and the marginating pool in the blood vessels. This is followed by an increased production of granulocytes; the production of monocytes and lymphocytes is not affected by IL-1. Administration of M-CSF had no significant effect on the production of granulocytes, lymphocytes, or monocytes in vivo. FIM specifically stimulated the production of monocytes and had no effect on the other cell lineages. Because FIM is synthesized and secreted by macrophages upon phagocytosis at the site of an inflammation, this study indicates that FIM is a monokine that acts as a long-range regulator to signal the bone marrow to increase monocyte production during an acute demand for more monocytes and (exudate) macrophages.