Effects of adherence, activation and distinct serum proteins on the in vitro human monocyte maturation process

C-Reactive Protein Signaling Pathways in Tumor Progression

Many cancers arise from sites of chronic inflammation, which creates an inflammatory microenvironment surrounding the tumor. Inflammatory substances secreted by cells in the inflammatory environment can induce the proliferation and survival of cancer cells, thereby promoting cancer metastasis and angiogenesis. Therefore, it is important to identify the role of inflammatory factors in cancer progression. This review summarizes the signaling pathways and roles of C-reactive protein (CRP) in various cancer types, including breast, liver, renal, and pancreatic cancer, and the tumor microenvironment. Mounting evidence suggests the role of CRP in breast cancer, particularly in triple-negative breast cancer (TNBC), which is typically associated with a worse prognosis. Increased CRP in the inflammatory environment contributes to enhanced invasiveness and tumor formation in TNBC cells. CRP promotes endothelial cell formation and angiogenesis and contributes to the initiation and progression of atherosclerosis. In pancreatic and kidney cancers, CRP contributes to tumor progression. In liver cancer, CRP regulates inflammatory responses and lipid metabolism. CRP modulates the activity of various signaling molecules in macrophages and monocytes present in the tumor microenvironment, contributing to tumor development, the immune response, and inflammation. In the present review, we overviewed the role of CRP signaling pathways and the association between inflammation and cancer in various types of cancer. Identifying the interactions between CRP signaling pathways and other inflammatory mediators in cancer progression is crucial for understanding the complex relationship between inflammation and cancer.

Temporal Analysis Reveals the Transient Differential Expression of Transcription Factors That Underlie the Trans-Differentiation of Human Monocytes to Macrophages

The activation of monocytes and their trans-differentiation into macrophages are critical processes of the immune response. Prior work has characterized the differences in the expression between monocytes and macrophages, but the transitional process between these cells is poorly detailed. Here, we analyzed the temporal changes of the transcriptome during trans-differentiation of primary human monocytes into M0 macrophages. We find changes with many transcription factors throughout the process, the vast majority of which exhibit a maximally different expression at the intermediate stages. A few factors, including AP-1, were previously known to play a role in immunological transitions, but most were not. Thus, these findings indicate that this trans-differentiation requires the dynamic expression of many transcription factors not previously discussed in immunology, and provide a foundation for the delineation of the molecular mechanisms associated with healthy or pathological responses that involve this transition.

C-reactive protein (CRP) induces chemokine secretion via CD11b/ICAM-1 interaction in human adherent monocytes

Several studies support C-reactive protein (CRP) as a systemic cardiovascular risk factor. The recent detection of CRP in arterial intima suggests a dual activity in atherosclerosis as a circulating and tissue mediator on vascular and immune cells. In the present paper, we focused on the inflammatory effects of CRP on human monocytes, which were isolated by Ficoll-Percoll gradients and cultured in adherence to polystyrene, endothelial cell monolayer, or in suspension. Chemokine levels, adhesion molecule, and chemokine receptor expression were detected by ELISA, flow cytometry, and real-time RT-PCR. Migration assays were performed in a Boyden chamber. Stimulation with CRP induced release of CCL2, CCL3, and CCL4 in adherent monocytes through the binding to CD32a, CD32b, and CD64, whereas no effect was observed in suspension culture. This was associated with CRP-induced up-regulation of adhesion molecules membrane-activated complex 1 (Mac-1) and ICAM-1 on adherent monocytes. Blockade of Mac-1/ICAM-1 interaction inhibited the CRP-induced chemokine secretion. In addition, CRP reduced mRNA and surface expression of corresponding chemokine receptors CCR1, CCR2, and CCR5 in adherent monocytes. This effect was a result of chemokine secretion, as coincubation with neutralizing anti-CCL2, anti-CCL3, and anti-CCL4 antibodies reversed the effect of CRP. Accordingly, a reduced migration of CRP-treated monocytes to CCL2 and CCL3 was observed. In conclusion, our data suggest an in vitro model to study CRP activities in adherent and suspension human monocytes. CRP-mediated induction of adhesion molecules and a decrease of chemokine receptors on adherent monocytes might contribute to the retention of monocytes within atherosclerotic lesions and recruitment of other circulating cells.

NAIP and Ipaf control Legionella pneumophila replication in human cells

In mice, different alleles of the mNAIP5 (murine neuronal apoptosis inhibitory protein-5)/mBirc1e gene determine whether macrophages restrict or support intracellular replication of Legionella pneumophila, and whether a mouse is resistant or (moderately) susceptible to Legionella infection. In the resistant mice strains, the nucleotide-binding oligomerization domain (Nod)-like receptor (NLR) family member mNAIP5/mBirc1e, as well as the NLR protein mIpaf (murine ICE protease-activating factor), are involved in recognition of Legionella flagellin and in restriction of bacterial replication. Human macrophages and lung epithelial cells support L. pneumophila growth, and humans can develop severe pneumonia (Legionnaires disease) after Legionella infection. The role of human orthologs to mNAIP5/mBirc1e and mIpaf in this bacterial infection has not been elucidated. Herein we demonstrate that flagellin-deficient L. pneumophila replicate more efficiently in human THP-1 macrophages, primary monocyte-derived macrophages, and alveolar macrophages, and in A549 lung epithelial cells compared with wild-type bacteria. Additionally, we note expression of the mNAIP5 ortholog hNAIP in all cell types examined, and expression of hIpaf in human macrophages. Gene silencing of hNAIP or hIpaf in macrophages or of hNAIP in lung epithelial cells leads to an enhanced bacterial growth, and overexpression of both molecules strongly reduces Legionella replication. In contrast to experiments with wild-type L. pneumophila, hNAIP or hIpaf knock-down affects the (enhanced) replication of flagellin-deficient Legionella only marginally. In conclusion, hNAIP and hIpaf mediate innate intracellular defense against flagellated Legionella in human cells.

A role for BLyS in the activation of innate immune cells

B-lymphocyte stimulator (BLyS) is a member of the tumor necrosis factor (TNF) ligand superfamily. Although BLyS costimulates adaptive immune cells, the ability of BLyS to stimulate innate immune cells has not been described. Here, we show that BLyS strongly induces human monocyte survival, and activation as measured by proinflammatory cytokine secretion and up-regulation of costimulatory molecule expression. In addition, monocytes cultured with BLyS differentiated into macrophage-like cells. Regarding BLyS receptor(s) expression, freshly isolated monocytes bound low levels of exogenous BLyS and expressed primarily intracellular TACI, and cell surface TACI levels increased following monocyte activation. Of interest, bone marrow monocytes from some multiple myeloma patients expressed significant levels of cell surface TACI at isolation. Our findings indicate that BLyS plays a role in activating innate immune cells. Moreover, this study may explain more clearly why high BLyS production is often correlated with certain inflammatory autoimmune diseases and B-lymphocyte malignancies.

Differential production of cytokines, reactive oxygen and nitrogen by bovine macrophages and dendritic cells stimulated with Toll-like receptor agonists

Toll-like receptors (TLR) have been described as partially sharing signalling pathways but showing unique ligand specificity and tissue distribution. Here, the response of bovine macrophages (Mphi) and dendritic cells (DC), both derived from monocytes, was compared by exposing them to the TLR-specific ligands lipopolysaccharide, poly(I:C)-double-stranded RNA, and CpG-DNA, as well as inactivated Gram-negative and Gram-positive bacteria, shown to bind to TLR. The production of NO, superoxide anion, interleukin-10 (IL-10), IL-12 and tumour necrosis factor (TNF) was determined. Compared to monocytes, Mphi expressed more TLR2 and similar levels of TLR4 mRNA transcripts, as analysed by quantitative polymerase chain reaction, whereas DC expressed reduced amounts. Although both DC and Mphi recognized the TLR ligands, dramatic differences were seen in their reaction pattern to them. Both cell types responded with the production of TNF, but DC produced more IL-12, whereas Mphi produced more IL-10, regardless of the TLR agonist used. Co-stimulation with interferon-gamma influenced the amount of cytokine production, but did not alter the cell type-specific response pattern. Compared to Mphi, DC produced > 10 times less NO upon triggering with TLR ligands. In addition, DC produced superoxide anion to opsonized and non-opsonized zymosan, but not to phorbol 12-myristate 13-acetate, a response pattern confirmed for human Mphi and DC, respectively. Different protein kinase C isoforms and extracellular signal-regulated kinase patterns were detected in cell lysates of resting and stimulated Mphi and DC. Collectively, our results point to profound differences in pathogen-derived signal-response coupling occurring commensurate with distinct functions carried out by Mphi or DC.

Strenuous resistive breathing induces plasma cytokines: role of antioxidants and monocytes

Inspiratory resistive breathing increases plasma cytokines, yet the stimulus (or stimuli) and source(s) remain unknown. We tested the role of reactive oxygen species as stimuli and of monocytes as sources of resistive breathing-induced cytokines. Six healthy subjects performed two resistive breathing sessions at 75% of maximum inspiratory pressure before and after a combination of antioxidants (vitamin E 200 mg, vitamin A 50,000 IU, and vitamin C 1,000 mg per day for 60 days, allopurinol 600 mg/day for 15 days, and N-acetylcysteine 2 g/day for 3 days before the second session). Blood was drawn before, at the end, and at 30 and 120 minutes after resistive breathing. Before antioxidants, plasma cytokine levels (determined by enzyme-linked immunosorbent assay) increased secondary to resistive breathing (tumor necrosis factor-alpha and interleukin [IL]-6 by twofold and IL-1beta by threefold). After antioxidants, plasma IL-1beta became undetectable. The tumor necrosis factor-alpha response to resistive breathing was abolished, and the IL-6 response was significantly blunted. Intracellular cytokine detection (by flow cytometry) showed no change in either the percentage of monocytes producing the cytokines or their mean fluorescence intensity both before and after antioxidants. We conclude that oxidative stress is a major stimulus for the resistive breathing-induced cytokine production and that monocytes play no role in this process.

Human autologous monocytes and monocyte-derived macrophages in co-culture with carcinoma F-spheroids secrete IL-6 by a non-CD14-dependent pathway

The secretion of interleukin (IL)-1 beta, IL-6 and tumour necrosis factor (TNF)-alpha were compared when freshly isolated autologous monocytes or monocytederived macrophages (MDMs) were co-cultured in vitro with autologous fragment (F)-spheroids established from a series of head and neck squamous cell carcinoma (HNSCC) patients. F-spheroids were generated from the malignant tumour (M-spheroids) or from benign mucosa (B-spheroids) from which the tumour originated control. If monocytes maturated towards MDMs before co-culture, the IL-6 secretion declined dependent on the extent of the MDM maturation by both M- and B-spheroid stimulation. When MDMs maturated in continuous co-culture, a steady-state secretion of IL-6 continued for several days but diminished when the culture medium was changed every 24 h. No co-culture-induced IL-1 beta or TNF-alpha was determined. Both the cytokine secretion and the mRNA gene expression revealed a different monocyte/MDM activation when co-culture and lipopolysaccharide (LPS)-stimulation were compared. Addition of anti-CD14 (10 microg/ml) decreased monocyte LPS-stimulated, but increased monocyte co-culture stimulated IL-6 secretion. In conclusion, M- and B-spheroids similarly stimulated monocytes and to a lesser extent MDMs. MDMs that maturated with F-spheroids present, retained responsiveness at the monocyte level. Co-culture-induced monocyte stimulation, as measured by IL-6 secretion, was not dependent on activation via the CD14 molecule.

Adherence-dependent calcium signaling in monocytes: induction of a CD14-high phenotype, stimulus-responsive subpopulation

Isolation of monocytes by plastic adherence alters cell morphology and function. In order to study the effects of cell isolation procedures and subsequent culture on monocyte function, we examined cytoplasmic calcium concentration changes (delta[Ca2+]in) in human monocytes isolated by either negative (magnetic bead) or positive (plastic adherence) selection then stimulated with formyl-Met-Leu-Phe (fMLP), either immediately after isolation, or after 48 h in culture. We have previously shown that fresh adherence-isolated monocytes respond to fMLP with small delta[Ca2+]in and oxidative burst responses, exhibiting larger responses following 48 h of incubation. We now demonstrate that fresh monocytes, prevented from adhering by negative selection, exhibit an even smaller fMLP-induced delta[Ca2+]in, which does not increase during 48 h in culture if cells are kept nonadherent, in Teflon. Calcium responses of adherent, fresh monocytes do not increase if cells are subsequently placed into suspension and maintained nonadherent, but increase if nonadherent cells are permitted to adhere to plastic. Furthermore, augmented fMLP-[Ca2+]in and oxidative burst responses in plastic-adherent cells are restricted to a CD14-high phenotype subpopulation. The CD14-high phenotype also describes a subpopulation of cells that responds to CD4 crosslinking with a rapid delta[Ca2+]in. Induction of a subpopulation of CD14-high expressing cells by adherence may explain in part maturation-induced response changes observed in macrophage but not in monocyte in vitro systems.

Vitreous body affects activation and maturation of monocytes into macrophages

BACKGROUND

Macrophages play an important role in several ocular diseases. Because macrophages localized in ocular tissues may be derived from blood monocytes, the effect of vitreous [containing transforming growth factor-beta 2 (TGF-beta 2) and hyaluronic acid] on blood monocytes, maturating in the tissue to macrophages, was determined.

METHODS

Human monocytes were cultured with and without vitreous in RPMI 1640 medium containing human AB serum. As a parameter of activation the release of interleukin-6 was measured by the B9 bioassay; as an indication of maturation, the content of acid phosphatase and the increase in cell size were assessed.

RESULTS

Monocytes in vitreous-containing medium grew more slowly than did control monocytes. Monocytes cultured in 10% vitreous released 51% less, and in 20% vitreous 73% less, interleukin-6 than control monocytes. Vitreous at 20% significantly (P = 0.0075) reduced the amount of acid phosphatase by 80% over a 4-day culture period. This reduction was partially eliminated with neutralizing antibodies to TGF-beta (P = 0.0014). Furthermore, human recombinant TGF-beta 2 increased the activity of acid phosphatase in monocytes at 1.25 ng/ml and reduced it (P < 0.0001) at higher concentrations (5-10 ng/ml). Hyaluronic acid showed an effect additive to that of TGF-beta in further diminishing the amount of acid phosphatase (P = 0.026).

CONCLUSION

Vitreous exerts a regulatory effect on monocyte activation and maturation by its content of TGF-beta and possibly hyaluronic acid and may, thus, modify the inflammatory or immune response in the eye.

Induction of nitric oxide synthase in bovine mononuclear phagocytes is differentiation stage-dependent

Bovine monocytes and monocyte-derived macrophages (MDM) activated by various means were assessed for induction of inducible nitric oxide synthase (iNOS), using the Griess assay, Northern blotting and reverse transcription/polymerase chain reaction (RT-PCR). Interferon-gamma (IFN-gamma) induced little, if any, iNOS expression and NO production in MDM, although these cells responded to IFN-gamma in other regards. In contrasts, MDM produced copious amounts of NO when stimulated with LPS or Salmonella dublin, and this was paralleled by high steady state levels of iNOS mRNA. Heat-killed Listeria monocytogenes induced more iNOS mRNA and nitrite than IFN-gamma, but much less than L. mono-cytogenes and IFN-gamma combined. Monocytes differed from M phi with respect to iNOS induction and nitrite production in several regards: (i) LPS and S. dublin induced only low levels of iNOS mRNA and nitrite in monocytes, although cells responded to these stimuli in various other ways: (ii) IFN-gamma alone induced in monocytes iNOS mRNA generation and NO formation, although to a low and variable degree; (iii) upon maximal stimulation (e.g. by L. monocytogenes and IFN-gamma combined), monocytes produced much less nitrite than MDM, and mRNA levels were lower. Regulation of macrophage iNOS varies considerably between species. We provide the first evidence in any species that the steady state levels of iNOS mRNA and NO generation in monocytes and macrophages activated by various means depend on the stage of mononuclear phagocyte differentiation.

Retinal pigment epithelial cell proliferation: potentiation by monocytes and serum

BACKGROUND

The development of proliferative vitreoretinopathy (PVR) results often from a breakdown of the blood-retina barrier and the intraocular accumulation of serum proteins and leukocytes, particularly monocytes, that then come into contact with retinal pigment epithelial (RPE) cells. To examine the effect of these two factors on RPE proliferation, which is characteristic of PVR, we used a coculture system of blood monocytes and human RPE cells.

METHODS

RPE cells were incubated with a variable number of monocytes at different serum concentrations and assayed for proliferation by [3H]-thymidine incorporation and cell counting. To assess cell-cell communication. RPE cells were labeled with 2', 7' -bis(carboxyethyl)-5(and 6) carboxyfluorescein acetoxy-methyl ester, and the dye transfer to monocytes was analyzed using an UV microscope.

RESULTS

Monocytes (P < 0.0004) and serum (P < 0.0001), each on its own, significantly stimulated RPE cell growth, and these two variables were interrelated (P < 0.0001), showing a potentiating synergism. In serum-free medium, monocytes increased proliferation to just above control levels, whereas the same number of monocytes in 5% serum increased the [3H]-thymidine incorporation 3.8 times. This effect was greatly reduced by prevention of direct cell contact by means of placement of a well insert, which also lessened the monocyte-induced proliferation in both serum-free and serum-containing medium. Furthermore, the transfer of the intracellular dye from RPE cells to cocultured monocytes indicates that RPE cells transferred parts of their cytoplasm to monocytes.

CONCLUSION

These observations underline the importance of protein leakage through a damaged blood-ocular barrier and of direct contact of monocytes/macrophages with RPE cells, as well as their reciprocal potentiating effect on RPE cell proliferation. Thus, early stabilization of the blood-ocular barrier, which would preclude or reduce protein leakage and invasion of inflammatory cells into the eye, could be a target for pharmacologic prevention of PVR.

Susceptibility of human monocytes to HIV type 1 infection in vitro is not dependent on their level of CD4 expression

Monocytes from HIV-seronegative persons were analyzed for CD4 expression and susceptibility to infection with HIV-1 on the day of isolation and following 1, 2, and 7 days in culture. Although surface CD4 was readily detected on freshly isolated monocytes, these cells were relatively resistant to infection. After 1 to 2 days in culture, when surface expression of CD4 had decreased over 90% to near background levels, cells became susceptible to infection with HIV-1. CD4 expression on monocytes cultured for 7 days was more than four times higher than that on freshly isolated cells, and the cultured cells were fully permissive to infection. These observations suggest that the differing susceptibility of monocytes and monocyte-derived macrophages to infection with HIV-1 is not simply proportional to the level of surface CD4 expression.

A system for assessment of monokine gene expression using human whole blood

Monocyte derived cytokines (monokines) are important mediators in inflammatory diseases and cancer. Control of monokine expression is also a major therapeutic target in autoimmune inflammation. Whole blood cultures permit examination of monokine expression under conditions which emulate the in-vivo environment whilst avoiding many of the artefacts associated with monocyte separation and culture. Here we describe a system for measuring interleukin-1 beta, interleukin-1 alpha, interleukin-6 and tumour necrosis factor-alpha mRNA in stimulated human whole blood ex-vivo, which can be applied to specimens from treated patients. Oligodeoxyribonucleotide probes are designed to allow standardisation of hybridisation and washing procedures. Washing and reprobing of membranes in appropriate sequence permits measurement of each monokine mRNA and mRNA for glyceraldehyde-3-phosphate dehydrogenase in only 7 ml of lipopolysaccharide-stimulated human blood. The method has been used successfully in studies of dexamethasone and methotrexate action on lipopolysaccharide stimulated IL-beta gene expression.

Monocyte differentiation and accessory function: different effects on the proliferative responses of an autoreactive T cell clone as compared to alloreactive or antigen-specific T cell lines and primary mixed lymphocyte cultures

An autoreactive T cell clone derived from a patient with reactive arthritis, two alloreactive T cell lines, two antigen-specific T cell lines and allogeneic resting T cells were analyzed for their responses to monocytes and macrophages derived from monocytes by in vitro differentiation. The autoreactive T cell clone strongly proliferated in response to fresh monocytes and to macrophages derived from a 7 day culture, but only poorly to monocytes cultured for 2 days. In contrast, alloreactive and antigen-specific T cell lines proliferated to all stimulatory cells equally well. Finally, primary mixed lymphocyte reactions could be stimulated by both fresh and 2-day cultured monocytes, but not by in vitro derived macrophages. The impaired response of the autoreactive T cell clone to 2-day cultured monocytes could not be attributed to reduced expression of several well-defined surface molecules nor to induction of nonresponsiveness. Neither allogeneic monocytes nor cytokines (IL-1, IL-2, IL-4, IL-6) could correct the defective response of the autoreactive T cell clone. However, preculture of monocytes in the presence of interferon-gamma, IL-1, IL-4 or IL-6 retained their stimulatory capacity. Our interpretation of the selectively impaired response of the autoreactive T cell clone is that it most likely recognizes a differentiation-dependent monocyte/macrophage-specific peptide.

Effects of purinergic agents on human mononuclear phagocytes are differentiation dependent. Implications for atherogenesis

The differentiation-dependent expression of purinergic receptors for metabolically stable analogues of adenosine and ATP was studied in human mononuclear phagocytes (MNPs). Ligands of these receptors are able to modulate cellular cholesterol metabolism. In addition, the intracellular signal transduction pathways of the purinergic receptor system were examined. ATP gamma S, the metabolic stable analogue of ATP, was used as a P2 ligand, and 2-p-(2-carboxyethyl)phenylethylamino-5'-N-ethylcarboxamido adenosine (CGS 21680) and 5'-(N-ethylcarboxamido)adenosine (NECA) were used as P1 ligands in binding studies. Binding of [35S]ATP gamma S to MNPs at 4 degrees C revealed saturable low-affinity binding sites with a Kd of 868 +/- 52 nmol/L and Bmax of 7.3 +/- 0.4 pmol per 10(6) cells in 1-day cultured human MNPs and a Kd of 780 +/- 30 nmol/L and Bmax of 14.0 +/- 0.8 pmol per 10(6) cells in 7-day cultured human MNPs. The characterization of the P1 receptors on 1- and 7-day cultured human MNPs showed that they are expressed only on 7-day cultured human MNPs. The specific binding curve of the adenosine A2 receptor agonist [3H]CGS 21680 was biphasic, with a Kd1 of 33 +/- 15 nmol/L and a Kd2 of 90 +/- 10 nmol/L and with Bmax1 of 0.19 +/- 0.06 pmol per 10(6) cells and Bmax2 of 0.41 +/- 0.09 pmol per 10(6) cells, whereas NECA did not exhibit specific binding. The typical agonists for probing A1 receptor subtypes did not bind to 1- and 7-day cultured human MNPs, indicating that only A2 receptors are expressed on 7-day cultured human MNPs. ATP gamma S enhanced [Ca2+]i in 1- and 7-day cultured human MNPs in a concentration-dependent manner, whereas the P1 ligands, adenosine and CGS 21680, induced Ca2+ flux only in 7-day cultured MNPs. All three drugs increased intracellular cAMP levels in 7-day cultured human MNPs at a concentration of 10(-5) mol/L, whereas no effect was observed in 1-day cultured human MNPs. The uptake of fluorescently labeled acetylated low-density lipoprotein (LDL) in 7-day cultured human MNPs was inhibited by adenosine, CGS 21680, ATP, and ATP gamma S. No significant influence of these compounds was measured on the uptake of LDL, acetylated LDL, and high-density lipoprotein, in 1-day cultured MNPs. Our investigations indicate that the expression of P2y and A2 receptors is increased during differentiation of blood monocytes to macrophages.(ABSTRACT TRUNCATED AT 400 WORDS)

Arachidonic acid metabolism of rat peritoneal macrophages after passive sensitization and allergen challenge

The aim of our work was to evaluate the effect of passive sensitization of rat peritoneal macrophages (treatment of cells by an anti-ovalbumin IgE-rich serum) on arachidonic acid (AA) metabolism and the impact of specific antigen (ovalbumin) on this process. Compared to a control treatment without serum, the atopic serum and a serum without IgE, used on [3H]AA-labeled macrophages, increased cyclooxygenase and lipoxygenase eicosanoid production. Sera, used prior to [3H]AA incorporation, induced a decrease of 3H-labeled membrane phospholipids and an increase of lipoxygenase metabolites in the [3H]AA incorporation medium. To establish if the serum-induced catabolism of AA differed according to whether it was externally added to the culture medium or incorporated into membrane phospholipids, we studied the eicosanoid secretion of [3H]AA-prelabeled macrophages, treated by the serum and incubated with [14C]AA. It was confirmed that phospholipid-incorporated AA was catabolised following the cyclooxygenase and lipoxygenase pathways and external AA preferentially following the lipoxygenase pathway. The allergen increased the eicosanoid formation of passively sensitized macrophages but not that of cells treated by the serum without IgE. Our data suggest that changes occurring in passive sensitization, on AA mobilization from membrane phospholipids and on AA catabolism, induced by the serum, are independent of IgE and must be taken into consideration on interpreting the allergen effect.

Longitudinal evaluation of peripheral blood monocyte secretory function in periodontitis-resistant and periodontitis-susceptible patients

The purpose of this investigation was to evaluate lipopolysaccharide (LPS)-stimulated monocyte secretory responses longitudinally in patients with generalized severe chronic adult periodontitis (periodontitis-susceptible) and controls with gingivitis (periodontitis-resistant). In addition, the expression of constitutive (Leu-M3) and LPS-inducible (Mo3e) antigens on monocytes isolated from these two groups was examined. Monocyte secretory function was assessed longitudinally; the effect of periodontal therapy in the susceptible patients was examined by comparing monocyte function before and after their treatment. Peripheral blood monocytes were isolated by counterflow centrifugal elutriation and treated with control medium or media containing 1 microgram/ml of Salmonella typhimurium LPS or Prevotella intermedia LPS with or without human recombinant interferon (IFN)-gamma pretreatment. Prostaglandin E2, F2 alpha and thromboxane B2 were quantified in culture samples by gas chromatography-mass spectrometry (GC-MS) and interleukin-1 beta was quantified by enzyme-linked immunosorbent assay. Leu-M3 and Mo3e antigen expression was assessed by FACScan. Three major findings were made. First, LPS-stimulated IL-1 beta release by monocytes from susceptible patients was depressed relative to that in resistant patients at the initial donation. After periodontal therapy, there was virtually identical IL-1 beta release in LPS-stimulated cultures from both groups. However, in susceptible patients IL-beta release was diminished after periodontal therapy in cultures pretreated with IFN-gamma. Second, there was a significant drift in monocyte secretion of prostaglandin E2 in samples from the resistant patients between the first two donations and the third donation. PGE2 release did not differ between groups at the initial donation, although there was a depression in PGE2 release in the susceptible group at the final donation when IFN-gamma was followed by S. typhimurium LPS.(ABSTRACT TRUNCATED AT 250 WORDS)

Down-regulation and release of CD14 on human monocytes by IL-4 depends on the presence of serum or GM-CSF

IL-4 induces down-regulation of CD14 expression on human monocytes only when the cells are cultured with serum. In serum-free cultures we failed to down-regulate CD14 by IL-4. Instead of serum, GM-CSF was required as a co-factor to restore the regulatory effect of IL-4 on CD14-expression. After 4 days of culture human monocytes were quantitatively CD14-negative as determined by flow-cytometry. On day 6, high amounts of CD14 molecules were detected in the SUP of these cultures, whereas intracellular immunofluorescence staining revealed no detectable CD14 in cytokine-treated monocytes. Thus, CD14 is lost by down-regulation (as shown by others) as well as by delivery into the medium. We previously hypothesized that dendritic cells may originate from monocytes. Our present finding support that one of the key markers, distinguishing monocytes/macrophages from dendritic cells, can be lost upon physiological stimuli.

Macrophage heterogeneity and differentiation: defined serum-free culture conditions induce different types of macrophages in vitro

Macrophages (MAC) are important effector cells of the immune system. They arise from circulating blood monocytes (MO), which undergo further maturation upon leaving the vasculature and migrating into the various tissues and body cavities. A similar differentiation process can be followed in vitro when monocytes are cultured in the presence of serum. In this study, different factors and serum proteins, either alone or in combination, were tested for their ability to promote the survival and/or maturation of blood MO in the absence of serum. Elutriation-purified MO cultured for 8 days on hydrophobic teflon foils in the presence of 5% human serum differentiated into large, well-spread MAC, whereas in the absence of serum, MO rapidly died. The serum-induced maturation of MAC was accompanied by a strong expression of CD16, CD14 and MAX antigens. Secretion of TNF-alpha and neopterin increased about 10-fold as compared with freshly isolated MO. The replacement of serum by either M-CSF (100 ng/ml) or immunoglobulin (0.5-5 mg/ml) had a marked effect on MO survival (about 50% of serum-cultured MO), but cells were smaller, less spread out and had low expression of CD16, CD14 and MAX antigens. Their functional competence in terms of TNF-alpha and neopterin release was reduced to 10-20% as compared with MAC cultured in the presence of serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake, distribution and fate of bacterial lipopolysaccharides in monocytes and macrophages: an ultrastructural and functional correlation

Bacterial lipopolysaccharides (LPS), which are important components of the cell wall of gram-negative bacteria, induce a number of host responses both beneficial and harmful. The present review elucidates the uptake, distribution and functions of LPS in mononuclear phagocytes in an attempt to gain an insight into the mechanisms which control the pathogenesis of LPS mediated septic shock. The unique feature of LPS bilayer structure, the tagged LPS and antibodies to LPS provide means for studying binding, uptake, fate and subcellular distribution of LPS in tissues and cells. LPS bind to monocytes and macrophages by specific interaction via receptors such as scavenger receptors, CD14 and CD18 and by non-specific interactions, and enter the cells via receptor-mediated endocytosis, absorptive pinocytosis, phagocytosis, and diffusion. The ingested LPS are localized in pinocytic vesicles, phagocytic vacuoles, cytoplasm, mitochondria, rough endoplasmic reticulum, Golgi apparatus, and nucleus. The interactions of LPS with monocytes and macrophages trigger a broad spectrum of cellular responses, including production of important bioactive factors or mediators, such as IL-1, TNF, interferons, prostaglandins, and macrophage-derived growth factor, which are implicated in the pathogenesis of septic shock and wound healing. However, there is no conclusive evidence indicating that production of the mediators can only be induced through specific interactions.

Tumour-cytolytic human monocyte-derived macrophages: a simple and efficient method for the generation and long-term cultivation as non-adherent cells in a serum-free medium

We report a simple and efficient culture procedure for the generation of tumour-cytolytic human monocyte-derived macrophages (MAC). In this method, normal human peripheral blood mononuclear cells, isolated using a conventional Ficoll-Hypaque density gradient procedure, are cultured as a heterogenous leukocyte population in Teflon or other hydrophobic cultureware, in a commercially available serum-free culture medium (M-SFM) that has been formulated specifically for the cultivation and ex vivo stimulation of human monocytes and MAC, and in the absence of exogenous mitogens, antigens, cytokines or other stimulants. This procedure features a negative-selection technique that takes advantage of the differential survival of blood leukocytes. Using the prescribed in vitro conditions, lymphocytes survived relatively poorly, whereas monocytes differentiated in the absence of exogenous stimulants into mature tumour-cytolytic MAC. The MAC were present as non-adherent, single cells that expressed good viability (greater than 95%) for a prolonged period (greater than 60 days). When compared to conventional procedures for generating MAC, the prescribed technique is thought to offer several important advantages in that it: (a) eliminates the tedious and cumbersome monocyte isolation procedures, thus providing a significant savings not only in time and money but also in eliminating repetitive cell manipulations that have often been associated with damage to monocyte morphology and/or function; (b) reduces the loss of monocyte subsets that are not recovered during specific isolation procedures; (c) facilitates harvesting a single cell, non-adherent suspension of immunocompetent MAC suitable for various examinations including analyses defining MAC morphology, cytochemistry, phenotype and function; and (d) eliminates variability and artifacts associated with different sera that are utilised frequently as medium supplements. The utility of the prescribed method is illustrated by the results of ongoing studies in which scanning electron microscopy and confocal laser scanning microscopy are being used to define MAC function in different immunological reactions, and examples of these observations are presented herein.

Immune-mediated interactions during macrophage development in non-Hodgkin's lymphoma

As part of an investigation of mononuclear phagocytes in malignant lymphoma, measurement of immune-mediated erythrophagocytosis and rosette formation was carried out on cells grown in suspension culture at the monocyte (Day 0) and macrophage (Day 6) stages; the culture medium contained autologous serum. Cells were derived from 10 patients with untreated non-Hodgkin's lymphoma (NHL) and from 12 normal individuals. The results were subjected to Analysis of Variance and demonstrated a significant difference between the two groups with respect to erythrophagocytosis but not to rosette formation. In the NHL group, the proportion of erythrophagocytic cells showed no significant increase between the monocyte and macrophage stages (0.07 to 0.09), in contrast to the marked increase seen in the normal group (0.09 to 0.24). In a pilot investigation to examine the possible role of factors in the serum, cells derived from the NHL patients were cultured with serum from healthy donors; they showed no significant difference in the immune-mediated functions from those grown in autologous serum. Overall, the results provide further quantitative evidence of defective macrophage maturation in NHL, presumably reflecting the compromise of host defence mechanisms.

Long term cultures of human monocytes in vitro. Impact of GM-CSF on survival and differentiation

In vitro differentiation of human monocytes (Mo) provides large amounts of mature and functionally competent macrophages (M phi) which may be used as potentially powerful anticancer agents for adoptive immunotherapy. Granulocyte macrophage-colony stimulating factor (GM-CSF) was evaluated for its ability to influence long term cultures of Mo-derived M phi. Large quantities of Mo isolated by leukapheresis and elutriation were cultured in non-adherent cell culture bags or in plastic flasks with or without GM-CSF. At various stages of differentiation, GM-CSF treated M phi were recovered and assayed for survival, morphology, surface antigens, functional properties and proliferation in comparison with control M phi. In the present paper, we demonstrate that GM-CSF at a concentration of 50 U/ml (5 ng/ml) promotes better cell survival and the differentiation of Mo into M phi displaying certain morphological differences as compared to control M phi such as an increased expression of Max-1 antigen, CR3 and Fc gamma II receptors, higher phagocytic properties and increased capacities of cytotoxicity and TNF secretion when the cells are further activated by IFN-gamma. Furthermore, GM-CSF treated cells exhibit a low-grade proliferation although the nature of the proliferating cells has not been entirely elucidated. We conclude that the GM-CSF treated M phi would be particularly suitable for adoptive immunotherapy.

Negative selection of human monocytes using magnetic particles covered by anti-lymphocyte antibodies

We have developed a standardized procedure for the isolation of monocytes from peripheral blood by negative selection using magnetic polymer particles coated with monoclonal antibodies against T and B lymphocytes. The average purity of the monocyte suspension was 85%, and monocyte recovery was 72% from Ficoll-Hypaque gradient separated mononuclear cells and 32% from whole blood. In a lucigenin enhanced chemiluminescence assay there was no significant difference between cells separated immunomagnetically and those separated on a gradient. Nor did electron microscopy show any significant difference in morphology between such monocytes. Negative selection using magnetic polymer particles is an efficient method for the separation of monocytes with intact morphology and function as measured by chemiluminescence.

Ultrastructural morphometry of human leucocytes in health and disease

In this review, the literature on ultrastructural morphometry of each of the main types of human blood leucocytes has been considered, together with the technical and numerical procedures essential for valid analysis. Quantitative data have been reported for these cell types in health and comparisons have been made with those in disease states. In monocytes, and in macrophages developing from them, subtle ultrastructural differences have been detected and quantitated in malignant lymphoma; as the mononuclear phagocytes were not themselves neoplastic, the changes may have related to defects in host defence. Change in the ultrastructural characteristics of leukaemic monoblasts have also been reported. Lymphocytes and malignant lymphoid cells have been extensively investigated: differences between different types and subsets have been shown to be present in both normal lymphocytes and their malignant counterparts in leukemias and lymphomas. Particular attention has been paid to morphometric assessment of nuclear shape and size in these disorders and to its possible value as a diagnostic tool. Granulocytes have so far been the subject of few morphometric studies, although in hypereosinophilic syndrome, cellular changes have been defined and have thrown light on the abnormal pattern of degranulation. There have also been scattered reports on the cells of acute myelogenous leukaemia. The use of computers and sophisticated statistical packages has greatly facilitated the application of multiple comparison procedures and has permitted discriminant analysis to be carried out where appropriate. This review shows that ultrastructural morphometry of leucocytes will have an increasing application in clinical pathology.

Evidence that exposure to fibrinogen or to antibodies directed against Mac-1 (CD11b/CD18; CR3) modulates human monocyte effector functions

We have recently shown that the treatment of fibrinogen-coated monocytes (MO) with anti-fibrinogen as well as the exposure of MO to surface-bound fibrinogen (Fg) or to albumin haptenized with the Fg C-gamma-terminal pentadecapeptide, induces on oxidative burst. Using chemiluminescence (CL) for indicating an oxidative burst, and the ingestion of IgG-coated erythrocytes as a test of phagocytosis, we have now studied the impact of Fg on MO effector functions. MO that had been either pretreated with Fg and washed, or that were exposed to surface-adsorbed Fg, exhibited impaired Fc receptor-mediated phagocytosis. A similar impairment was observed when MO were pretreated with activating agents such as phorbol myristate acetate, n-formyl-methionyl-leucyl-phenylalanine (fMLP) or the calcium ionophore A23187. Moreover, following exposure to Fg or IgG, MO exhibited a reduced oxidative burst upon stimulation with a variety of agents. Similarly, MO pretreated or coincubated with anti-Mac-1 exhibited a reduced oxidative burst upon stimulation. Our results raise the possibility that inflammatory mononuclear phagocytes experience a functional modulation upon encountering fibrin by interacting with specific receptors for fibrin(ogen). This type of modulation is analogous to effects induced by the triggering of Fc gamma receptors. MO showed a decreased oxidative burst when either pretreated or coincubated with anti-Mac-1 antibodies, whereas antibodies directed against other MO surface constituents had no, or a weak effect only. This is compatible with the suggestion that Mac-1 acts as a fibrin (ogen) receptor.

Low-affinity interaction of fibrinogen carboxy-gamma terminus with human monocytes induces an oxidative burst and modulates effector functions

The interaction of highly purified, monomeric fibrinogen (Fg) with human monocytes (MO) was investigated. In contrast to commercial Fg, no high-affinity binding of monomeric Fg to MO or mononuclear cells could be demonstrated. MO preincubated with Fg in the presence or absence of Ca++ elicited an oxidative burst when triggered with anti-Fg antibodies. Divalency of the antibody and specificity were required, but an intact Fc portion was not. Surface-adsorbed monomeric Fg also promoted an oxidative burst. Evidence is presented that Fg-MO interaction is mediated by the carboxy-gamma terminus of Fg. MO treated with monomeric Fg or exposed to Fg-coated surfaces show a reduced oxidative burst upon triggering with unrelated stimuli. Thus, MO function may be modulated upon interaction with surface-adsorbed Fg or with fibrin.

Plasma protein adsorbed biomedical polymers: activation of human monocytes and induction of interleukin 1

These studies involved the evaluation of human monocyte/macrophage activation by biomedical polymers coated with human blood proteins. The biomedical polymers were polyethylene, polydimethylsiloxane, woven Dacron fabric, expanded polytetrafluoroethylene, Biomer, and tissue culture treated polystyrene as the control. They were adsorbed with human blood proteins: albumin, fibrinogen, fibronectin, hemoglobin, and gamma globulin. The protein adsorbed polymers were evaluated for their potential to activate the monocyte/macrophage cellular population in vitro as assessed by the induction of the monocyte/macrophage inflammatory mediator, Interleukin 1 (IL1). Suppression of IL1 was observed when protein adsorbed polymers were compared to the appropriate protein adsorbed control. Protein adsorbed polymers, when compared to polymers without protein adsorption, stimulated IL1 production. The data presented in this manuscript show the level of induction and secretion of IL1 was dependent on the biomedical polymer and the protein adsorbed, as well as the requirement of lipopolysaccharide. These results show differential interactions occur between the proteins, monocytes/macrophages, and biomedical polymers which alter activation and induction of IL1.

Disordered development of macrophages in non-Hodgkin's lymphoma

Macrophage development in 20 untreated patients with non-Hodgkin's lymphoma (NHL) has been studied and compared with that in 20 normal subjects. Morphometric measurements were carried out on ultrastructural features of cell, nucleus and mitochondria during 6 days suspension culture of blood monocytes in the presence of autologous serum and lymphocytes. The results were subjected to multivariate and univariate analysis of variance. Statistically significant differences were found between the subject groups with respect to the volumes and surface areas of cell, nucleus and mitochondria, to the excess surface membrane of cell and nucleus (as compared with equivalent spheres) and to the number of mitochondrial profiles per section. It would appear that the patients' cell grew less, showed less elaboration of surface features and had reduced nuclear and mitochondrial development, the latter affecting mitochondrial numbers rather than individual size. The findings provide further evidence that mononuclear phagocytes are deranged in NHL.

Fibrinogen association with human monocytes: evidence for constitutive expression of fibrinogen receptors and for involvement of Mac-1 (CD18, CR3) in the binding

Radiolabeled fibrinogen (Fg) specifically binds to mononuclear leukocytes (MNL) and to purified monocytes, but not to nylon-nonadherent lymphocytes. The association is rapid, Ca++-dependent and reversible. MNL containing Fg-binding monocytes had not been exposed to endotoxin (less than 4 pg/mL) during the isolation and the binding test, and Fg binding was not altered by preincubation of MNL with lipopolysaccharide. The binding of Fg was inhibited by anti-Mac-1 antibodies (OKM1). Antibodies to surface-bound Fg were able to induce luminol-dependent chemiluminescence, indicating that Fg binding sites have receptor function. Emission of a signal depended on MNL exposure to Fg, on specific, divalent antibodies, but not on the antibody Fc portion. These data show that human monocytes constitutively express specific Fg receptors and suggest that Mac-1, a member of the integrin superfamily, is involved in Fg recognition.