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PubMed1998

In vitro-differentiated embryonic stem cell macrophages: a model system for studying atherosclerosis-associated macrophage functions.

Monocytes/macrophages (Mo) appear to play a critical role in the initiation and progression of atherosclerotic lesions. In this study, we characterized in vitro-differentiated embryonic stem (ES) cell macrophages as a model system for studying atherosclerosis-associated Mo functions. Using immunofluorescence staining and Western analysis, we demonstrate that ES Mo express typical macrophage cell surface markers, as well as the known receptors for modified forms of low density lipoprotein (LDL), including the Mo scavenger receptors (SR-A type I and type II), CD36, and CD68. Differentiated ES Mo specifically bind and degrade 125I-labeled acetylated LDL with high affinity, and their incubation with acetylated LDL (15 microg/mL) for 48 hours produces characteristic "foamy" Mo, as visualized by oil red O staining. ES Mo also express matrix-degrading metalloproteinases (MMP-3, MMP-9), which have been implicated in collagen breakdown in the fibrous cap of atherosclerotic plaques, and secrete cytokines (tumor necrosis factor-alpha, interleukin-6) in response to inflammatory stimuli. Transfection experiments, using a green fluorescent protein reporter gene, driven by the myeloid-specific promoter, CD11b, demonstrated that ES Mo can also be used to study macrophage-restricted gene expression in vitro. Taken together, these data demonstrate that ES Mo exhibit many properties typical of arterial lesion macrophages. Its ease of genetic manipulation makes it an attractive system for investigations of macrophage functions in vitro.

Antigens, CD↗
PubMed2002

Increased macrophage inflammatory protein-1alpha and macrophage inflammatory protein-1beta levels in bronchoalveolar lavage fluid of patients affected by different stages of pulmonary sarcoidosis.

Macrophage inflammatory protein (MIP)-1alpha and MIP-1beta are two CC chemokines that induce lymphocyte migration. MIP-1alpha preferentially mediates chemotaxis of CD8 rather than CD4 lymphocytes, whereas the reverse is true for MIP-1beta. Both these chemokines recognize CCR5 as a cellular receptor in T lymphocytes and alveolar macrophages. We measured the concentrations of MIP-1alpha and MIP-1beta in bronchoalveolar lavage fluid (BALF) of 30 subjects affected by different stages of pulmonary sarcoidosis and 18 healthy normal subjects. We also evaluated the expression of CCR5 in alveolar macrophages and lymphocytes. The BALF concentrations of MIP-1alpha were significantly increased only in Stage II and III sarcoidosis. On the contrary, the concentrations of MIP-1beta were significantly increased at all stages. A striking increase of CCR5 expression was observed in both lymphocytes and macrophages of all patients, along with a trend to decreased positivity from Stage I to III of the disease. The MIP-1beta concentrations correlated with the number of total (r = 0.65, p = 0.0001) and both CD4 (r = 0.64, p = 0.0001) and CD8 (r = 0.62, p = 0.0001) lymphocytes; on the contrary, the MIP-1alpha concentrations correlated only with CD8 lymphocytes (r = 0.45, p = 0.002). Finally, significant negative correlations were observed between the neutrophil percentage and CCR5 expression in alveolar macrophages (r = -0.53, p = 0.005) and lymphocytes (r = -0.43, p = 0.01). Our results help to explain the mechanism of CD4 and CD8 recruitment and the possible involvement of CC chemokines in the fibrotic progression of sarcoidosis.

Adult↗
PubMed1996

Interleukin 13 inhibits macrophage inflammatory protein-1 alpha production from human alveolar macrophages and monocytes.

Interleukin 13 (IL-13) is a recently described protein secreted by activated T cells and is a potent in vitro modulator of human monocyte and B-cell functions. IL-13 shares some biologic properties as well as structural similarities with IL-4. Macrophage-inflammatory protein 1 alpha (MIP-1 alpha) is a product of activated monocytes and macrophages and an important activator of T cells, monocytes, and macrophages. We determined the effect of human recombinant IL-13 on lipopolysaccharide (LPS)- and IL-1 beta-induced MIP-1 alpha mRNA and protein expression from peripheral blood monocytes (PBM) and alveolar macrophages (AM). In PBM, basal MIP-1 alpha protein was 20 +/- 7 pM and increased following LPS and IL-1 beta to 1,520 +/- 193 (P < 0.001) and 233 +/- 50 (P < 0.003) pM. IL-13 (25 ng/ml) reduced these values by 55 +/- 10% [not significant (NS)], 43 +/- 9% (P < 0.03), and 44 +/- 15% (NS), respectively. LPS- and IL-1 beta-induced MIP-1 alpha mRNA expression was reduced by 43 +/- 5% (P < 0.01) and 41 +/- 4% (NS). In AM, IL-13 reduced LPS-induced MIP-1 alpha protein release of 2,030 +/- 242 pM by 32 +/- 8% (P < 0.05) and MIP-1 alpha mRNA by 27 +/- 1% (NS). For both PBM and AM, the inhibitory effect of IL-13 on MIP-1 alpha protein was maximal at 24 h, was dose dependent with a maximal effect at 100 ng/ml, and was similar to, although slightly less potent than, that seen with IL-4. In PBM, the inhibitory effect of IL-13 required de novo protein synthesis and was not due to enhanced mRNA decay. Thus, IL-13 has inhibitory effects on the transcription of MIP-1 alpha from monocytes and macrophages, and as is the case with IL-4 and IL-10, may be an important mediator for suppressing inflammatory responses.

Blotting, Northern↗
PubMed2001

Alveolar macrophage deficiency in osteopetrotic mice deficient in macrophage colony-stimulating factor is spontaneously corrected with age and associated with matrix metalloproteinase expression and emphysema.

Macrophage colony-stimulating factor (M-CSF) is one of several hematologic growth factors capable of regulating the survival, proliferation, and differentiation of macrophages, but its role in modulation of the accumulation and function of alveolar macrophages (AMs) in vivo is not well defined. Osteopetrotic (Op/Op) mice have no detectable M-CSF and show variable tissue-specific reductions in macrophage numbers. It was hypothesized that AMs would be decreased in number and have altered function in Op/Op mice because of the absence of M-CSF. Lung macrophages identified by Mac-3 staining in lung sections were decreased in number in 20-day-old Op/Op mice (P <.001) but not Op/Op mice older than 4 months (P =.68) compared with findings in age-matched littermate controls. The numbers of AMs recovered by bronchoalveolar lavage (BAL) were also reduced in young but not adult Op/Op mice compared with controls. Expression of interleukin-3 (IL-3) was increased in the lungs of Op/Op mice compared with controls as determined by quantification of IL-3 cytokine levels (P =.04), bioactivity (P =.02), and messenger RNA transcript levels. AMs of Op/Op mice spontaneously released higher levels of matrix metalloproteinases (MMPs) than AMs of controls as determined by immunohistochemical staining of AMs and zymographic assessment of BAL fluid and AM lysates. Consistent with an increased release of MMP, Op/Op mice had abnormal elastin deposition and spontaneously developed emphysema in the absence of molecular or cellular evidence of lung inflammation. These data show that the AM deficiency observed in young Op/Op mice is spontaneously corrected with age and is associated with increased lung levels of IL-3, spontaneous MMP expression by AMs, and destruction of lung tissue.

Age Factors↗
PubMed2001

Paracrine interactions of chondrocytes and macrophages in cartilage degradation: articular chondrocytes provide factors that activate macrophage-derived pro-gelatinase B (pro-MMP-9).

Cells of the monocyte/macrophage lineage are involved in the development of inflammatory joint diseases such as rheumatoid arthritis. This disease is characterized by cartilage degradation and synovial membrane inflammation with a progressive loss of joint function. The pathological processes are still not well understood. Therefore it would be interesting to develop a suitable experimental in vitro model system for defined studies of monocyte/macrophage and chondrocyte interactions at the molecular level. For that purpose we cocultured chondrocytes from adult human articular cartilage with human monocytes and macrophages for defined periods of time in agarose without addition of serum. We performed zymographic and western blot analysis of culture medium, completed by quantitative RT-PCR of each chondrocyte, monocyte and macrophage RNA, respectively. The reliability of the newly established coculture systems is confirmed by causing a clear decrease of intact aggrecan in the coculture medium plus concurrent appearance of additional smaller fragments and a reduction of chondrocyte aggrecan and collagen II gene expression in the presence of monocytes. In culture medium from cocultures we detected active forms of the matrix metalloproteinases MMP-1, MMP-3 and MMP-9 accompanied by induction of gene expression of MMP-1, membrane type 1 MMP (MT1-MMP) and tissue inhibitor of metalloproteinase 2 (TIMP-2) in chondrocytes. No gene expression of MMP-9 was detectable in chondrocytes, the enzyme was solely expressed in monocytes and macrophages and was downregulated in the presence of chondrocytes. Our results suggest that MMP-9 protein in coculture medium originated from monocytes and macrophages but activation required chondrocyte-derived factors. Because addition of plasmin, a partial activator of pro-MMP-3 and pro-MMP-1, enhanced the activation of pro-MMP-9 and pro-MMP-1 in cocultures but not in monocultured macrophages, and the presence of MMP-3 inhibitor II prevented pro-MMP-9 activation, we assumed a stepwise activation process of pro-MMP-9 that is dependent on the presence of at least MMP-3 and possibly also MMP-1.

Adult↗
PubMed1994

Laminin promotes proliferation of bone marrow-derived macrophages and macrophage cell lines.

We examined the effect of laminin on DNA synthesis or cell growth of bone marrow-derived macrophages (BMM) and five macrophage cell lines including two factor-dependent macrophage cell lines (BDM-1 and BDM-1W3) and three factor-independent ones (BAM3, J774.1, and P388D1). Laminin stimulated the M-CSF-dependent proliferation of BMM and BDM-1 cells in a dose-dependent manner, but it had no effect on the proliferation of BDM-1W3 cells. This stimulatory effect was modified by increasing the concentration of fetal calf serum in the culture medium. Laminin also stimulated the proliferation of BAM3 and J774.1 cells, whereas it could not stimulate that of P388D1 cells. Taken together, these results suggest that the differences in the response of these macrophage cell lines to the presence of laminin may be derived from the difference in the state of maturation of these cells. Although laminin acted as a potent mitogenic factor when it was added to the culture medium, the stimulation was two- to threefold lower when dishes were coated with equivalent amounts of laminin. When BDM-1 cells were cultured with laminin, they underwent drastic morphological changes. A monoclonal antibody that recognizes the integrin alpha 6 subunit only partially inhibited the mitogenic effect of laminin. The results in this report suggest that laminin may participate in the regulation of macrophage populations in vivo.

Amino Acid Sequence↗
PubMed2001

Macrophage response to Mycobacterium tuberculosis during HIV infection: relationships between macrophage activation and apoptosis.

Human macrophages represent the first line of defense for the containment of Mycobacterium tuberculosis infection. After phagocytosis, macrophages express activation surface markers and produce proinflammatory cytokines and chemokines whose main role is to control pathogen spreading by recruiting peripheral lymphocytes and monocytes at the site of inflammation. However, in the case of a concomitant human immunodeficiency virus (HIV) infection, these signals strongly enhance the susceptibility to viral infection both at the viral entry and replication levels. Under these conditions, viral expansion extends beyond tissue macrophages to T cells and vice-versa, according to the emerging viral phenotype. In absence of an efficient immune response, Mycobacterium tuberculosis can replicate in macrophages in an uncontrolled fashion culminating in macrophage death by apoptosis. As a consequence, a more severe form of immunedepression, involving both innate and specific immune responses, could be responsible for both ematogenous mycobacterial dissemination and extrapulmonary form of tuberculosis in HIV-infected patients.

Apoptosis↗
PubMed2002

Activation of the stem cell-derived tyrosine kinase/RON receptor tyrosine kinase by macrophage-stimulating protein results in the induction of arginase activity in murine peritoneal macrophages.

Regulation of macrophage activities in response to inflammatory stimuli must be finely tuned to promote an effective immune response while, at the same time, preventing damage to the host. Our lab and others have previously shown that macrophage-stimulating protein (MSP), through activation of its receptor RON, negatively regulates NO production in response to IFN-gamma and LPS by inhibiting the expression of inducible NO synthase (iNOS). Furthermore, activated macrophages from mice harboring targeted mutations in RON produce increased levels of NO both in vitro and in vivo, rendering them more susceptible to LPS-induced endotoxic shock. In this study, we demonstrate that stimulation of murine peritoneal macrophages with MSP results in the RON-dependent up-regulation of arginase, an enzyme associated with alternative activation that competes with iNOS for the substrate L-arginine, the products of which are involved in cell proliferation and matrix synthesis. Expression of other genes associated with alternative activation, including scavenger receptor A and IL-1R antagonist, is also up-regulated in MSP-stimulated murine macrophages. Stimulation of cells with IFN-gamma and LPS blocks the ability of MSP to induce arginase activity. However, pretreatment of cells with MSP results in the up-regulation of arginase and inhibits their ability to produce NO in response to IFN-gamma and LPS, even in the presence of excess substrate, suggesting that the inhibition of NO by MSP occurs primarily through its ability to regulate iNOS expression.

Animals↗
PubMed2004

Macrophage-stimulating protein, the ligand for the stem cell-derived tyrosine kinase/RON receptor tyrosine kinase, inhibits IL-12 production by primary peritoneal macrophages stimulated with IFN-gamma and lipopolysaccharide.

IL-12, produced by APCs during the initial stages of an immune response, plays a pivotal role in the induction of IFN-gamma by NK and gammadeltaT cells and in driving the differentiation of Th1 cells, thus providing a critical link between innate and acquired immunity. Due to the unique position occupied by IL-12 in the regulation of immunity, many mechanisms have evolved to modulate IL-12 production. We have shown previously that macrophage-stimulating protein (MSP), the ligand for the stem cell-derived tyrosine kinase/recepteur d'origine nantais (RON) receptor, inhibits NO production by macrophages in response to IFN-gamma and enhances the expression of arginase. Mice lacking RON exhibit increased inflammation in a delayed-type hypersensitivity reaction and increased susceptibility to endotoxic shock. In this study we demonstrate that pretreatment of macrophages with MSP before IFN-gamma and LPS results in the complete inhibition of IL-12 production due to suppression of p40 expression. This response is mediated by the RON receptor, and splenocytes from RON(-/-) animals produce increased levels of IFN-gamma. MSP pretreatment of macrophages resulted in decreased tyrosine phosphorylation of Stat-1 and decreased expression of IFN consensus sequence binding protein in response to inflammatory cytokines. In addition to IL-12, the expression of IL-15 and IL-18, cytokines that are also dependent on IFN consensus sequence binding protein activation, is inhibited by pretreatment with MSP before IFN-gamma and LPS. We also show that the ability of MSP to inhibit IL-12 production is independent of IL-10. Taken together, these results suggest that MSP may actively suppress cell-mediated immune responses through its ability to down-regulate IL-12 production and thus inhibit classical activation of macrophages.

Animals↗
PubMedDate not supplied

Expression and regulation of the macrophage inflammatory protein-1 alpha gene by nicotine in rat alveolar macrophages.

Cigarette smoking causes inflammation mainly confined to the airway and lung. Nicotine is one of the primary constituents in cigarette smoke. Alveolar macrophages apparently play a pivotal role in mediating pulmonary inflammation via the production of chemokines. Macrophage inflammatory protein-1 alpha (MIP-1 alpha), a member of CC chemokines, has been shown to contribute to monocyte/macrophage and neutrophil chemotaxis and activation. Our previous work demonstrated that MIP-1 alpha mRNA expression in macrophages is induced by a variety of stimuli. In the present study, we further investigate whether nicotine can regulate the gene expression of MIP-1 alpha in macrophages and determine the mechanism leading to increased expression. A rat alveolar macrophage (RAM) cell line, NR8383, was treated with nicotine at a dose of 3.1, 31, 310 microM, or 3.1 mM. Northern blot analysis showed that the induction of MIP-1 alpha mRNA expression was dose-dependent. To define the time course of the inflammatory response, RAM cells were exposed to 31 microM nicotine, MIP-1 alpha mRNA was induced as early as 1 h after treatment, was maximally expressed at 4 and 6 hours, and reduced by 8 hours. Western blot analysis demonstrated a single band with an estimated molecular weight of 10 kD for MIP-1 alpha which was induced after nicotine treatment, suggesting that expression of MIP-1 alpha mRNA could reflect in protein synthesis. In addition. the increase in MIP-1 alpha mRNA expression induced by nicotine was attenuated by co-treatment with the antioxidant N-acetylcysteine (NAC), at doses of 10 and 20 mM, suggesting that the induction of MIP-1 alpha mRNA is mediated via the generation of reactive oxygen species (ROS). To further investigate transcriptional regulation of the MIP-1 alpha gene expression, RAM cells were exposed to nicotine. MIP-1 alpha mRNA levels were significantly increased in nuclear RNA preparations, indicating that transcriptional activation is involved in increased expression of MIP-1 alpha mRNA. Moreover, we performed RNA decay assay by measuring the half-life of MIP-1 alpha mRNA. Treatment of RAM cells with the transcriptional inhibitor actinomycin D following exposure to nicotine revealed that the half-life of MIP-1 alpha mRNA was markedly increased by nicotine treatment, supporting a role of post-transcriptional stabilization in MIP-1 alpha gene expression. These observations indicate that nicotine can induce MIP-1 alpha mRNA expression and protein synthesis in RAM cells, mediating, at least in part, via the generation of ROS. In addition, the increase in MIP-1 alpha mRNA level involves, both transcriptional activation and post-transcriptional stabilization.

Animals↗
PubMed1990

Regulation of macrophage activation by IL-3. I. IL-3 functions as a macrophage-activating factor with unique properties, inducing Ia and lymphocyte function-associated antigen-1 but not cytotoxicity.

Here we report that IL-3 (also referred to as multi-CSF because of its colony-stimulating activity on a variety of hemopoietic cell lineages) can function as a macrophage-activating factor (MAF). IL-3 was able to regulate the expression of class II MHC Ag and the cellular interaction molecule lymphocyte function-associated Ag-1 on the surface of murine peritoneal exudate cells. The kinetics of IL-3-induced Ia expression appeared to be distinct from that induced by either IFN-gamma, IL-4, or granulocyte-macrophage-CSF. IL-3 was also distinguished from these factors by the finding that it did not induce macrophage tumoricidal activity. In addition to its inherent MAF activities, IL-3 also showed a marked synergy with low doses of LPS (0.05 to 0.5 ng/ml) as well as IFN-gamma in Ia induction. When lymphocyte function-associated Ag-1 expression was evaluated, the effects of these stimuli appeared to be only additive. Although LPS has been shown to inhibit IFN-gamma-induced Ia expression, in our experiments this property of LPS is manifest only when present at doses greater than or equal to 50 ng/ml. At lower concentrations, LPS potentiated both IL-3- and IFN-gamma-induced class II MHC Ag expression. Data presented here also suggest that the synergistic interactions between low doses of LPS and IL-3 are not mediated by known LPS-inducible cytokines of macrophage origin, because rIL-1, TNF-alpha, or IL-6 did not enhance the response to IL-3. Because IL-3 can also participate in the regulation of IL-1 expression, it appears that IL-3 can function as a MAF which selectively regulates the accessory cell characteristics required for Ag presentation, as opposed to the cytolytic functions of the macrophage.

Animals↗
PubMed1989

Impaired macrophage activation in vitamin D3 deficiency: differential in vitro effects of 1,25-dihydroxyvitamin D3 on mouse peritoneal macrophage functions.

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) is known to interact in vitro with mononuclear phagocytes. The purpose of this study was to determine the role of the steroid in macrophage activation in vivo. Peritoneal macrophages from normal and vitamin D3-deficient mice were obtained after i.p. injection of activating or eliciting agents. Cells obtained from vitamin D3-deficient mice exhibited defected capabilities to perform anti-tumor activities (cytostasis and cytolysis) and to form oxygen reduction products (H2O2 and O2-). On the other hand, the level of the lysosomal enzyme acid phosphatase was unaffected by vitamin D3 deficiency. In vitro, incubation of macrophages with 1,25(OH)2D3 enhanced their anti-tumor activities, but did not affect the cells' capacity to produce H2O2 and O2-, or acid phosphatase. Our results suggest that 1,25(OH)2D3 is essential for macrophage activation in vivo. However, in vitro, the hormone is only partially capable of affecting the macrophage functions, probably because of the maturation state of the cells.

Acid Phosphatase↗
PubMed1988

Effects of granulocyte-macrophage colony-stimulating factor and colony-stimulating factor-1 on the proliferation and differentiation of murine alveolar macrophages.

Murine alveolar macrophages (AM) were shown to have proliferative ability and to form colonies in vitro. The factors in lung-conditioned medium (CM) and L929-CM which stimulate the proliferation of AM were considered to be granulocyte-macrophage colony-stimulating factor (GM-CSF) and CSF-1, respectively, because recombinant murine (rm)GM-CSF and recombinant human (rh)CSF-1 could replace the activities of lung-CM and L929-CM, respectively. The phenotype of the cells in the colonies formed by AM incubated with rmGM-CSF or lung-CM was AM-like; more than 90% of the cells were stained by anti-asialo GM1 but not by FITC-LPS, and had AM-like morphology. Expression of Mac-1 Ag determined by M1/70HL in these cells as well as original AM was low. However, the phenotype of the cells in the colonies formed by AM incubated with rhCSF-1 or L929-CM was peritoneal macrophage (PM)-like; more than 90% of the cells were stained by FITC-LPS and M1/70HL, but not by anti-asialo GM1, and showed PM-like morphology. The cells in the colonies formed by AM incubated with rmGMCSF changed their phenotype after treatment with rhCSF-1; the percentage of cells stained by anti-asialo GM1 decreased, and that of cells stained by FITC-LPS increased. The cells in the colonies formed by AM incubated with rhCSF-1 never changed their phenotype after incubation with rmGM-CSF. In contrast to AM, more than 90% of the cells in all colonies formed by PM incubated with either rmGM-CSF, rhCSF-1, lung-CM, or L929-CM were stained by FITC-LPS but not by anti-asialo GM1. These results show that although AM and PM can proliferate, AM, in contrast to PM, are bipotential cells that can differentiate into two types of macrophages responding to distinct types of CSF, and that one of the molecular mechanisms controlling macrophage heterogeneity may be based on the type of CSF produced at distinct tissues.

Animals↗
PubMed1987

Interleukin 2 receptors are expressed by alveolar macrophages during pulmonary sarcoidosis and are inducible by lymphokine treatment of normal human lung macrophages, blood monocytes, and monocyte cell lines.

Expression of receptors for IL 2 was believed initially to be restricted to T cells after their activation by IL 1 and antigen. However, recently IL 2 receptors (IL 2R) were demonstrated on activated B cells by using an anti-IL 2R monoclonal antibody (anti-Tac). In this study, we examined the capacity of cultured human alveolar macrophages, blood monocytes, and myelomonocytic (HL-60) or monoblast (U937) cell lines to bind three different anti-IL 2R monoclonal antibodies before or after stimulation with the monocyte-activating agents IFN-gamma, LPS, phorbol ester, or lymphokine-containing conditioned medium. For each of the four cell populations examined, resting unstimulated cells bound little or no anti-IL 2R antibody, as shown independently by quantitative cell binding assay and by immunoperoxidase labeling. By contrast, incubation with recombinant IFN-gamma, conditioned medium, or to a lesser extent, native or recombinant IL 2 itself, resulted in a significant enhancement of anti-IL 2 receptor monoclonal antibody binding by all four populations, whereas LPS, PMA, or IL 1 had no effect. In addition, membrane binding of anti-Tac antibody, similar to that seen after stimulation of normal lung macrophages with IFN-gamma, was detected by using macrophages obtained by bronchoalveolar lavage of five patients with active pulmonary sarcoidosis. These findings are consistent with the expression of a functional IL 2R on activated cells of the monocyte lineage, since anti-Tac binding to IFN-gamma-treated HL-60 cells was inhibited by addition of excess IL-2; specific binding of anti-IL 2 monoclonal antibodies was detected in the presence of exogenous IL 2; and a 50 to 55 kD molecule was immunoprecipitated from both activated lung macrophages and T lymphoblasts by using anti-Tac antibody. We conclude that human mononuclear phagocytes can be induced by lymphokines to express IL 2R, and that such IL 2R+ macrophages can be detected in vivo during inflammation.

Cell Line↗
PubMed1978

[Use of 51Cr-labelled macrophages for the objective evaluation of macrophage migration inhibition].

A possibility of using 51Cr-labeld macrophages migrating from the capillaries and lysed with sodium dodecyl sulfate for objective and quantitative assessment of the results of macrophage migration inhibition (MMI) microassay was demonstrated on the basis of correlation analysis of the experimental data. Migration area and sensitivity of 51Cr-labeled macrophages to the action of the factor of migration inhibition were found not to differ from those of unlabeled macrophages. In the assessment of the absolute macrophage migration values and its reduction under the action of the factor of migration inhibition formed in the H-2 system, and also of the specificity of this reduction there was revealed a high correlation between the migration area and the value of the migrant cell label.

Animals↗
PubMed1979

A sensitive technique for measuring specific macrophage aggregation: a comparison with macrophage migration inhibition, for the detection of lymphokine activity.

A new quantitative method for the measurement of macrophage aggregation, induced by lymphokine preparations, is described. This involves the continuous measurement of the light absorbance of stirred macrophage suspensions. The results have been compared with those obtained by measuring macrophage migration inhibition activity for the detection of lymphokine activity. Separation of crude lymphocyte culture supernatants by Sephadex G-200 shows that the material with aggregating activity is heterogeneous. The greater amount of this activity is not separated from macrophage migration inhibition activity, and has a molecular weight of 35,000--70,000. A comparison has been made with other published methods for measuring macrophage aggregation.

Cell Aggregation↗
PubMed1993

Inside-out integrin signaling in macrophages. Analysis of the role of the alpha 6A beta 1 and alpha 6B beta 1 integrin variants in laminin adhesion by cDNA expression in an alpha 6 integrin-deficient macrophage cell line.

Leukocytes use the alpha 6 beta 1 integrin to adhere to laminin based on mAb inhibition and affinity chromatography studies. This adhesion requires leukocyte stimulation with either PMA or specific cytokines, a process that has been termed "inside-out" integrin signaling. In the present study, the involvement of alpha 6 integrin structural variants in this regulated adhesion was examined using mouse macrophages. The two known alpha 6 structural variants, alpha 6A and alpha 6B, differ only in their cytoplasmic domain sequences. Using reverse transcriptase-polymerase chain reaction, we observed that macrophages express only the alpha 6A structural variant, in contrast to most cell types which express both alpha 6A and alpha 6B variants. The role of this integrin subunit in macrophage adhesion was assessed by cDNA transfection of P388D1 cells. We found that this mouse macrophage cell line does not adhere to laminin even in response to phorbol 12-myristate 13-acetate (PMA) stimulation, though it does adhere normally to fibronectin and tissue culture plastic. Subsequent analysis employing reverse transcriptase-polymerase chain reaction and immunoprecipitation of surface labeled cells revealed that this cell line expresses neither the alpha 6A nor alpha 6B integrin subunits. Stable transfection of either the chick or human alpha 6A cDNAs into P388D1 cells resulted in chimeric alpha 6A beta 1 surface expression. The alpha 6A transfectants exhibited inside-out integrin signaling because PMA stimulation markedly increased their ability to adhere to laminin but it did not increase alpha 6A beta 1 surface expression. Similar results were obtained after transfection of the human alpha 6B cDNA. Analysis of the human transfectants was facilitated by the generation of a monoclonal antibody, 2B7, that is specific for the human alpha 6 integrin subunit. These observations demonstrate that both alpha 6A beta 1 and alpha 6B beta 1 can be regulated by inside-out signaling pathways in macrophages, even though this cell type expresses only alpha 6A beta 1. The data presented also demonstrate clearly that the alpha 6A and alpha 6B cytoplasmic domains do not differ in their ability to be regulated by PMA.

Amino Acid Sequence↗
PubMed1993

Granulocyte-macrophage colony-stimulating factor-induced antibody-dependent cellular cytotoxicity in bone marrow macrophages: application in bone marrow transplantation.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been reported to induce antitumor activity in peripheral blood monocytes. We examined the role of GM-CSF on bone marrow (BM) macrophages in inducing antibody-dependent cellular cytotoxicity (ADCC) against murine and human tumor cells in vitro and in vivo with the aim of applying this approach in an autologous bone marrow transplantation (BMT) setting. GM-CSF induced a potent ADCC in BM macrophages against a murine melanoma in vitro. Treatment with GM-CSF alone or with antibody alone had no effect, whereas therapy with combination of both these agents resulted in a significant reduction in dissemination of melanoma both in a nontransplant as well as in BMT settings, with results being more optimal in the latter setting. Adoptive transfer of BM macrophages harvested from mice undergoing therapy with GM-CSF plus antibody significantly reduced the dissemination of melanoma in secondary recipients but only after irradiation, not in intact mice. GM-CSF also induced significant ADCC in human BM macrophages against a melanoma and a lymphoma in vitro and against a lymphoma implanted in nude mice in vivo. Again, these effects were more optimal after chemotherapy. These data suggest that treatment with GM-CSF plus tumor-specific monoclonal antibodies after BMT may induce an antitumor effect and help eradicate the minimal residual disease.

Animals↗