Expression of monocyte chemoattractant protein 1 in macrophage-rich areas of human and rabbit atherosclerotic lesions.

The recruitment of monocyte-macrophages into the artery wall is one of the earliest events in the pathogenesis of atherosclerosis. Monocyte chemoattractant protein 1 (MCP-1) is a potent monocyte chemoattractant secreted by many cells in vitro, including vascular smooth muscle and endothelial cells. To test whether it is expressed in the artery in vivo, we used Northern blot analysis, in situ hybridization, and immunocytochemistry to study the expression of MCP-1 in normal and atherosclerotic human and rabbit arteries. Northern blot analysis showed that MCP-1 mRNA could be isolated from rabbit atherosclerotic lesions but not from the intima media of normal animals. Furthermore, MCP-1 mRNA was extracted from macrophage-derived foam cells isolated from arterial lesions of ballooned cholesterol-fed rabbits, whereas alveolar macrophages isolated simultaneously from the same rabbits did not express MCP-1 mRNA. MCP-1 mRNA was detected by in situ hybridization in macrophage-rich regions of both human and rabbit atherosclerotic lesions. No MCP-1 mRNA was found in sublesional medial smooth muscle cells or in normal arteries. By using immunocytochemistry, MCP-1 protein was demonstrated in human lesions, again only in macrophage-rich regions. Immunostaining of the serial sections with an antiserum against malondialdehyde-modified low density lipoprotein indicated the presence of oxidized low density lipoprotein indicated the presence of oxidized low density lipoprotein and/or other oxidation-specific lipid-protein adducts in the same areas that contained macrophages and MCP-1. We conclude that (i) MCP-1 is strongly expressed in a small subset of cells in macrophage-rich regions of human and rabbit atherosclerotic lesions and (ii) MCP-1 may, therefore, play an important role in the ongoing recruitment of monocyte-macrophages into developing lesions in vivo.     

Elevated expression of monocyte chemoattractant protein 1 by vascular smooth muscle cells in hypercholesterolemic primates.

Atherosclerosis is marked by an overt inflammatory infiltrate, with enhanced recruitment of monocytes/macrophages observed in both human and experimental atherosclerosis. We previously determined that monocyte chemoattractant protein 1 (MCP-1) accounts for virtually all of the chemotactic activity produced by vascular (aortic) smooth muscle cells in culture. We now report that arteries from a primate model of atherosclerosis with dietary-induced hypercholesterolemia exhibit increased levels of MCP-1 mRNA expression in vivo, whereas their normal counterparts demonstrate minimal MCP-1 expression. Furthermore, immunohistochemistry and in situ hybridization clearly indicate that the expression of MCP-1 protein and mRNA is in the smooth muscle cells of the medial layer of the artery and in monocyte-like and smooth muscle-like cells found in the overlying intimal lesion. These studies indicate that one of the responses to dietary hypercholesterolemia is the expression of MCP-1 by vascular smooth muscle cells. This expression, when augmented with other cellular and molecular factors, could significantly contribute to the recruitment of monocytes/macrophages to the vessel wall.     

Induction of monocyte- and T-cell-attracting chemokines in the lung during the generation of idiopathic pneumonia syndrome following allogeneic murine bone marrow transplantation

Idiopathic pneumonia syndrome (IPS) is a significant complication following bone marrow transplantation (BMT). We have developed a murine model in which severe IPS is induced by pre-BMT conditioning and allogeneic T cells and is characterized by the recruitment of host monocytes and donor T cells into the lung by day 7 post-BMT. Chemokines regulate cellular recruitment and the migration of cells into inflammatory lesions. In this study, we examined the profiles of chemokines produced locally in the lung (parenchyma and bronchoalveolar lavage fluid) and systemically (serum) during the generation of IPS in the peri-BMT period. Protein and messenger RNA (mRNA) levels of CC chemokines (monocyte/lymphocyte attractants), especially monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1alpha, RANTES (regulated upon activation normal T-cell expressed and secreted), and C10, were preferentially induced in the lung by day 7 postallogeneic BMT. In addition, there was an increase in mRNA for IP-10 (a monocyte and Th1-cell chemoattractant). The CXC chemokines MIP-2 and KC, known neutrophil attractants, were moderately elevated. For the most part, these increases in chemokines were dependent on the coinfusion of allogeneic T cells with the BM inoculum. Ribonuclease protection assay and in situ hybridization analyses post-BMT showed that the lung was a major producer of MCP-1, a potent inducer of monocyte chemotaxis. Increases in MCP-1 levels in the lung preceded host APC influx whereas MIP-1alpha levels accompanied donor T-cell infiltration. In summary, we have shown that monocyte- and T-cell-attracting chemokines are associated with monocyte and T-cell recruitment during IPS.     

Clinical significance of MCP-1 levels in BALF and serum in patients with interstitial lung diseases.

It has previously been reported that the expression of monocyte chemoattractant protein-1 (MCP-1) in the lung tissues of patients with idiopathic pulmonary fibrosis (IPF) was different from that in the tissues of patients with other interstitial lung diseases (ILDs). The aim of this study was to determine whether this difference reflects the amount of MCP-1 in the bronchoalveolar lavage fluid (BALF) or serum of patients with ILD, and whether such a correlation, if it exists, is clinically useful. MCP-1 concentrations in the BALF and sera were evaluated in 86 patients with ILDs including IPF, acute interstitial pneumonia, interstitial pneumonia with collagen vascular disease (IP-CVD), chronic interstitial pneumonia (CIP), bronchiolitis obliterans-organizing pneumonia, sarcoidosis, hypersensitivity pneumonitis, and in 10 normal healthy volunteers who were controls (NC). BALF MCP-1 levels were significantly elevated in the IPF, IP-CVD, CIP and sarcoidosis groups compared with the NC group. The level in the IPF group was significantly higher than that in any other patient group. Serum MCP-1 levels in the IPF, IP-CVD, CIP and sarcoidosis groups were significantly higher than the NC group. No statistical difference was found in serum MCP-1 levels between the IPF, IP-CVD and CIP groups. BALF MCP-1 levels were significantly higher than serum MCP-1 levels in the IPF group and lower than in the IP-CVD and CIP groups. Serum MCP-1 levels correlated with the clinical course of ILD treated with corticosteroid therapy. These results show that measurement of monocyte chemoattractant protein-1 levels in both bronchoalveolar lavage fluid and serum may be helpful in discriminating idiopathic pulmonary fibrosis from other types of interstitial lung disease and that monitoring of serum monocyte chemoattractant protein-1 may be useful for predicting the clinical course of interstitial lung diseases.     

Regulation of monocyte chemoattractant protein 1 by cytokines and oxygen free radicals in rat hepatic fat-storing cells

BACKGROUND & AIMS: Monocyte chemoattractant protein 1 (MCP-1) is a potent monocyte/macrophage chemoattractant expressed by fat-storing cells (FSCs) in rat models of liver injury. This study investigated the mechanism of this activation of hepatic MCP-1 expression. METHODS: The regulation of MCP-1 messenger RNA (mRNA) expression and protein synthesis was examined in FSC lines derived from CCl4-induced cirrhotic rat liver (cirrhotic FSCs) and normal rat liver (normal FSCs). RESULTS: Northern blot hybridization analysis revealed low levels of MCP-1 mRNA in cultured cirrhotic FSCs that increased markedly after treatment with tumor necrosis factor alpha, interleukin 1 alpha, or transforming growth factor beta 1. All three cytokines increased the synthesis and secretion of MCP-1 protein. Oxygen free radical production also increased MCP-1 mRNA levels. These increases in MCP-1 mRNA were blocked by dexamethasone. In normal FSCs, levels of MCP-1 mRNA and secreted protein were increased in response to cytokines or oxygen free radical production, but the magnitude and duration of this increase was less than in cirrhotic FSCs. CONCLUSIONS: In liver injury, monocyte/macrophage recruitment and activation from FSC production of MCP-1 may be stimulated by cytokines and oxygen free radicals. During chronic liver injury leading to cirrhosis, FSCs may become hypersensitive to these stimuli, further fueling the inflammatory response. (Gastroenterology 1996 Jun;110(6):1870-7)     

Elevated bronchoalveolar concentrations of MCP-1 in patients with pulmonary alveolar proteinosis.

Pulmonary alveolar proteinosis (PAP) is a rare disease of unknown aetiology characterized by accumulations of lipoproteinaceous material within the alveoli. The alveolar macrophages become increasingly foamy, and are thought to have a role in the pathogenesis of PAP. However, the mechanisms of macrophage recruitment are unclear. In the bronchoalveolar lavage fluid (BALF) of four patients with PAP and 20 normal control subjects, the following were examined: the monocyte chemotactic activity due to the chemokine monocyte chemoattractant protein (MCP)-1 with the use of a chemotactic chamber assay, the levels of MCP-1 by enzyme-linked immunosorbent assay, and the MCP-1 expression on lavage cells by immunocytochemistry and in situ hybridization. The monocyte chemotactic activity in the BALF of the PAP patients was markedly elevated, and the activity was completely absorbed by treatment with anti-MCP-1. The MCP-1 levels in the BALF were surprisingly high in the PAP group (25,100+/-472 pg x mL(-1)), whereas low levels of MCP-1 were detected in the normal control subjects (mean: never smokers 4.8; smokers 10.4 pg x mL(-1)). MCP-1 protein and messenger ribonucleic acid were expressed by macrophages from the PAP patients, and the expression was reduced according to foaming of the cells; there were monocyte-like macrophages with strong expression, small foamy cells with moderate expression, large foamy cells with a faint expression of MCP-1, and ghost cells with no expression. However, the increase of macrophage number in the PAP BALF was relatively small. These data suggest that monocyte chemoattractant protein(-1) expression by alveolar macrophages represents an amplification mechanism for the recruitment of additional macrophages to the alveoli in pulmonary alveolar proteinosis. It is possible that an ingestion of an excess of alveolar materials in pulmonary alveolar proteinosis may impair the macrophage function and the survival, resulting in the lack of a prominent increase in the macrophage number in bronchoalveolar lavage fluid.     

Idiopathic Pulmonary Fibrosis is Associated with Circulating Antiepithelial Antibodies

Purpose

Idiopathic pulmonary fibrosis (IPF) is a restrictive fibrotic lung disease of uncertain etiology. Alveolar epithelial injury may be one of the inciting triggers in the pathogenesis of this disorder. We hypothesized that circulating antibodies to alveolar epithelial and endothelial cells may be involved in the pathogenesis of IPF.

Methods

Antibodies to alveolar epithelial and endothelial cells were analyzed by indirect immunofluorescence using alveolar epithelial cells (A549) and human umbilical vein endothelial cells respectively. IgG and IgM antibodies in patients’ serum were evaluated. Patterns of immunofluorescence, including membranous, cytoplasmic, and nuclear staining, were analyzed by fluorescence microscopy. The severity of immunofluorescence was divided into mild, moderate, and severe categories. Fifty-six patients (IPF?=?28, non-IPF ILD?=?9, non-ILD control?=?19) were evaluated for antiepithelial antibodies, and 28 patients (IPF?=?12, non-IPF ILD?=?3, non-ILD control?=?13) were studied for antiendothelial antibodies.

Results

Compared with control subjects, serum from IPF patients displayed significantly higher IgG binding to alveolar epithelial cells (P?=?0.041) with a membranous pattern of immunofluorescence. However, there was no significant difference in immunofluorescence with IgG on endothelial cells (P?=?0.165). In terms of IgM antibodies, there was no differential fluorescence observed for either epithelial or endothelial cells.

Conclusions

There is evidence of increased IgG antibodies directed against alveolar epithelium in IPF. These antibodies may play a significant role in the pathogenesis of this fibrotic disorder. The findings of this study suggest further evaluation of the role of immune mediated alveolar epithelial injury in IPF.     

Alveolar JE/MCP-1 and endotoxin synergize to provoke lung cytokine upregulation, sequential neutrophil and monocyte influx, and vascular leakage in mice

The C-C chemokine monocyte chemotactic protein 1 (JE/MCP-1) is a key cytokine for lung monocyte recruitment, and may be detected in high levels in the alveolar space in lung injury. We hypothesized that alveolar JE/MCP-1 might synergize with endotoxin in this compartment to elicit lung inflammatory events. Intratracheal instillation of JE/MCP-1 into BALB/c mice did not provoke increased bronchoalveolar lavage tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), and macrophage inflammatory protein 2 (MIP-2) levels, but elicited monocyte recruitment into this compartment. Intratracheal Escherichia coli endotoxin provoked elevated lavage TNF-alpha, IL-6, and MIP-2 levels, peaking after 6 h in parallel with increased alveolar neutrophil numbers, in the absence of vascular leakage. Mice receiving both endotoxin and JE/ MCP-1 showed drastically increased lavage TNF-alpha, IL-6, and MIP-2 levels, 22-fold higher lavage neutrophil numbers, and lung vascular leakage. Moreover, an 8-fold increased alveolar accumulation of monocytes, peaking at 48 h together with expansion of the resident alveolar macrophage pool, was noted. Intraperitoneal instead of alveolar deposition of MCP-1 or endotoxin failed to reproduce the synergistic response, and the same was true for employment of RANTES instead of MCP-1. Blockade of neutrophil recruitment by anti-CD18 did not affect the intra-alveolar cytokine response to MCP-1 plus endotoxin. Together, JE/MCP-1 and endotoxin, when coappearing in the alveolar compartment at low dosage, elicit an early phase of lung inflammatory injury with increased cytokine synthesis and neutrophil recruitment, and a late phase of enhanced monocyte traffic and expansion of the alveolar macrophage pool.     

Inhibition of apelin expression switches endothelial cells from proliferative to mature state in pathological retinal angiogenesis

The recruitment of mural cells such as pericytes to patent vessels with an endothelial lumen is a key factor for the maturation of blood vessels and the prevention of hemorrhage in pathological angiogenesis. To date, our understanding of the specific trigger underlying the transition from cell growth to the maturation phase remains incomplete. Since rapid endothelial cell growth causes pericyte loss, we hypothesized that suppression of endothelial growth factors would both promote pericyte recruitment, in addition to inhibiting pathological angiogenesis. Here, we demonstrate that targeted knockdown of apelin in endothelial cells using siRNA induced the expression of monocyte chemoattractant protein-1 (MCP-1) through activation of Smad3, via suppression of the PI3K/Akt pathway. The conditioned medium of endothelial cells treated with apelin siRNA enhanced the migration of vascular smooth muscle cells, through MCP-1 and its receptor pathway. Moreover, in vivo delivery of siRNA targeting apelin, which causes exuberant endothelial cell proliferation and pathological angiogenesis through its receptor APJ, led to increased pericyte coverage and suppressed pathological angiogenesis in an oxygen-induced retinopathy model. These data demonstrate that apelin is not only a potent endothelial growth factor, but also restricts pericyte recruitment, establishing a new connection between endothelial cell proliferation signaling and a trigger of mural recruitment.     

Inflammatory-activated microvascular endothelial cells regulate interleukin-8 and monocyte chemoattractant protein-1 expression of A549 cells in a paracrine fashion

Increased levels of interleukin (IL)-8 and monocyte chemoattractant protein (MCP)-1 have been found in bronchoalveolar lavage fluid of acute respiratory distress syndrome (ARDS) patients. The authors investigated whether inflammatory-activated microvascular pulmonary endothelial cells (HMVECL) regulate expression of IL-8 and MCP-1 in the alveolar epithelial cell line A549 and studied the effects of hypoxia (5% O(2)) and hyperoxia (85% O(2)). The authors observed significant up-regulation of IL-8 and MCP-1 expression in A549 cells that was independent from the IL-1 receptor pathway but was modified by oxygen tension. These data show that the pulmonary microvascular endothelium is able to regulate epithelial cell chemokine expression in a paracrine fashion.     

三种细胞因子表达在特发性肺纤维化中的作用

目的 观察血小板衍生的生长因子（ＰＤＧＦ）、ＡＡ、ＢＢ及转化生长因子（ＴＧＦ）β在特发性肺间质纤维化（ＩＰＦ）支气管灌洗细胞及开胞肺活检标本的蛋白及基因表达，探索其在ＩＰＦ发病中的作用。方法 用免疫组化方法检测７例ＩＰＦ患支气管灌洗细胞ＰＤＧＦ，ＴＧＦ－β蛋白和基因的表达。结果 在肺间质纤维化患支气管灌洗细胞中，ＰＤＧＦ－ＡＡ，ＰＤＧＦ－ＢＢ〉ＴＧＦ－β均定位于肺泡巨噬细胞。三种不同的细胞因子     

Modulation of atherogenesis by chemokines

Migration of leukocytes into the vasculature-which involves the concerted effort of many molecules, including chemokines-is a requisite step for atherogenesis. The three chemokines that have been implicated most strongly in atherogenesis are monocyte chemoattractant protein 1 (MCP-1), interleukin 8 (IL-8)/growth-regulated oncogene alpha (Gro-alpha), and fractalkine. Although all three chemokines appear to impact atherogenesis by attenuating monocyte/macrophage accumulation in the lesion, the precise mechanism of action of each of the chemokines, as well as their interactive role in atherosclerosis, have not been elucidated. This review focuses on the latest findings that describe the individual roles of MCP-1, IL-8/Gro-alpha, and fractalkine on macrophage recruitment in atherosclerosis. Furthermore, based on present knowledge of the participation of these three chemokines and their receptors in monocyte/macrophage recruitment, a possible interactive role of these chemokines in atherogenesis is explored.     

类法尼醇X受体在巨噬细胞中下调单核细胞趋化蛋白1的表达

目的研究小鼠巨噬细胞株ANA-1中类法尼醇X受体的表达情况,并进一步研究类法尼醇X受体天然配体鹅脱氧胆酸在ANA-1中对单核细胞趋化蛋白1表达的影响,以探讨类法尼醇X受体在动脉粥样硬化发生发展中的作用。方法应用逆转录聚合酶链反应检测类法尼醇X受体在ANA-1细胞中的表达,及鹅脱氧胆酸处理后单核细胞趋化蛋白1的转录水平,Westernblot检测类法尼醇X受体的表达及其激活后对自身蛋白表达的调节,以及单核细胞趋化蛋白1蛋白的表达水平。结果类法尼醇X受体在ANA-1中表达,并依赖鹅脱氧胆酸浓度自我上调,鹅脱氧胆酸能显著下调单核细胞趋化蛋白1的表达水平(P<0.05)。结论类法尼醇X受体在小鼠巨噬细胞株ANA-1中组成型表达并呈配体浓度依赖性自我上调,类法尼醇X受体激活后可通过直接或间接方式下调单核细胞趋化蛋白1的表达。     

Molecular pathways of monocyte emigration into the alveolar air space of intact mice.

The adhesive interactions involved in monocyte recruitment to the alveolar space in vivo are only poorly defined. To study these interactions, we used a recently developed mouse model that allowed the separation and quantification of freshly recruited monocytes, resident alveolar macrophages (rAM), neutrophils, and lymphocytes in the bronchoalveolar compartment by fluorescence activated cell sorting technology. In these mice, the combined intratracheal administration of the monocyte chemoattractant JE/monocyte chemotactic protein (MCP)-1 and low dose Escherichia coli lipopolysaccharide (LPS) induces a self-limiting pulmonary inflammatory response, characterized by well-controlled sequelae of both neutrophil and monocyte emigration into the alveolar space. In contrast, challenge with JE/MCP-1 provokes the emigration only of monocytes in the absence of lung inflammation. Using an array of function-blocking monoclonal antibodies (mAb) (anti-CD11a, -CD11b, -CD18, -CD49d, -CD54, and -CD106), we characterized the adhesive interactions underlying the transendothelial and transepithelial leukocyte traffic in intact animals. Alveolar monocyte recruitment elicited by JE/MCP-1 alone was strictly dependent on CD11b/CD18, CD54, and CD49d, and partly dependent on CD11a, but not dependent on CD106. In response to JE/MCP-1 plus E. coli LPS, we observed additional engagement of CD11a and CD106 for enhanced alveolar monocyte transmigration. Comigrating neutrophils were found to primarily utilize CD11b, CD18, and CD54, but not CD49d, CD106, or, surprisingly, CD11a. This contrasted with the effect of CD11a on alveolar challenge with macrophage inflammatory protein (MIP)-1alpha instead of JE/MCP-1. In conclusion, we found that in an intact mouse model allowing detailed phenotyping of leukocyte traffic into the alveolar space, the molecular pathways involved in JE/MCP-1-driven monocyte efflux differed under noninflammatory and inflammatory (presence of LPS) conditions. Moreover, the profile of adhesive interactions underlying the monocyte efflux differed from that characterizing neutrophil trafficking.     

Asbestos exposure induces MCP-1 secretion by pleural mesothelial cells

We showed previously that both crocidolite and chrysotile asbestos inhalation induced a persistent macrophage inflammatory response within the pleural space of the rat. We postulated that the stimulus for pleural macrophage recruitment after asbestos exposure was the induction of monocyte chemoattractant protein-1 (MCP-1) synthesis by pleural mesothelial cells. To test this hypothesis, rat pleural mesothelial cells (RPMC) were cultured with or without chrysotile or crocidolite asbestos fibers (8 micrograms/cm2) in the presence (50 ng/mL) or absence of either tumor necrosis factor-alpha (TNF-alpha) or interleukin-1 beta (IL-1 beta). MCP-1 mRNA expression was assessed by RT-PCR in RPMC cultured for 2 to 24 hours, and MCP-1 protein secretion was measured by ELISA in conditioned medium from 24-hour and 48-hour cultures. Crocidolite and chrysotile fibers induced MCP-1 mRNA expression in RPMC which was maximal after 12 hours in the absence of cytokines, but which peaked after 2 hours when RPMC were challenged with asbestos + TNF-alpha or IL-1 beta. Both types of asbestos also significantly increased MCP-1 protein secretion after 24 and 48 hours (P < .0001), an effect that was potentiated by cytokine stimulation. Rats exposed by inhalation to either chrysotile or crocidolite asbestos fibers also had greater amounts of MCP-1 protein in their pleural lavage fluid than did sham-exposed rats. These findings suggest that MCP-1 secretion by RPMC may have a role in the initiation and/or potentiation of asbestos-induced pleural injury.     

Basic fibroblast growth factor and its receptors in idiopathic pulmonary fibrosis and lymphangioleiomyomatosis

Basic fibroblast growth factor (bFGF) is a potent mitogenic factor for smooth muscle cells, myofibroblasts, and fibroblasts, proliferation of which is a hallmark of idiopathic pulmonary fibrosis (IPF) and lymphangioleiomyomatosis (LAM). Mast cells produce bFGF and have been associated with pulmonary fibrosis. We hypothesize that smooth muscle cell/myofibroblast-like cells will be spatially associated with bFGF-containing mast cells and that bFGF receptors will be expressed on the effector cells in IPF and LAM. We performed quantitative immunohistochemistry for bFGF, mast cell tryptase, smooth muscle actin for smooth muscle cell/myofibroblast-like cells, and fibroblast growth factor receptors (Flg, Bek) and measured collagen and elastic fiber in lung sections from IPF (n = 14), LAM (n = 9), and control lung (n = 10). IPF and LAM lung contained more smooth muscle cell/myofibroblast-like cells than did control lung. bFGF-containing mast cells were abundant both in IPF and LAM and were associated with collagen, elastic fibers, and smooth muscle cell/myofibroblast-like cells in IPF. Flg was expressed on epithelial cells, endothelial cells, smooth muscle cell/myofibroblast-like cells, and macrophages in IPF. In LAM, Flg was expressed on epithelial cells adjacent to smooth muscle cell/myofibroblast-like cell aggregates. Bek was expressed dominantly on smooth muscle cell/myofibroblast-like cells in LAM and on smooth muscle cell/myofibroblast-like cells as well as neutrophils in IPF. These data suggest that mast cell-derived bFGF might exert fibrogenic, proliferative effects on smooth muscle cell/myofibroblast-like cells through its receptors.     

Monocyte chemoattractant protein-1 accelerates atherosclerosis in apolipoprotein E-deficient mice.

The pro-inflammatory chemokine, monocyte chemoattractant protein-1 (MCP-1), plays a fundamental role in monocyte recruitment and has been implicated as a contributing factor to atherosclerosis. The predominant cell types within the vessel wall--endothelial cells, smooth muscle cells, and macrophages--all contribute to overexpression of MCP-1 in atherosclerotic tissue. In this report we assess the role of MCP-1 expression by leukocytes on lesion progression in a murine model susceptible to atherosclerosis. Bone marrow cells from mice overexpressing a murine MCP-1 transgene on a background of apoE-deficiency or from control mice were transplanted into irradiated apoE-knockout mice. After repopulation of apoE-knockout mice with bone marrow containing the MCP-1 transgene, macrophages expressing the MCP-1 transgene were found in several tissues, including the aorta. Qualitative assessment of atherosclerosis in these mice revealed increased lipid staining, a 3-fold (P<0.001) increase in the amount of oxidized lipid, and increased immunostaining for macrophage cell surface markers with anti-F4/80 and anti-CD11b antibodies. There were no differences in plasma lipids, plasma lipoprotein profiles, or body weight between the 2 groups. These results provide the first direct evidence that MCP-1 expression by leukocytes, predominately macrophages, increases the progression of atherosclerosis by increasing both macrophage numbers and oxidized lipid accumulation.