Exploring biomarkers associated with deteriorating vascular health using a targeted proteomics chip: The SABPA study.

ABSTRACT: In this observational study, by the use of a multiplex proteomic platform, we aimed to explore associations between 92 targeted proteins involved in cardiovascular disease and/or inflammation, and phenotypes of deteriorating vascular health, with regards to ethnicity.Proteomic profiling (92 proteins) was carried out in 362 participants from the Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA) study of black and white African school teachers (mean age 44.7 ±â€Š9.9 years, 51.9% women, 44.5% Black Africans, 9.9% with known cardiovascular disease). Three proteins with <15% of samples below detectable limits were excluded from analyses. Associations between multiple proteins and prevalence of hypertension as well as vascular health [Carotid intima-media thickness (cIMT) and pulse wave velocity (PWV)] measures were explored using Bonferroni-corrected regression models.Bonferroni-corrected significant associations between 89 proteins and vascular health markers were further adjusted for clinically relevant co-variates. Hypertension was associated with growth differentiation factor 15 (GDF-15) and C-X-C motif chemokine 16 (CXCL16). cIMT was associated with carboxypeptidase A1 (CPA1), C-C motif chemokine 15 (CCL15), chitinase-3-like protein 1 (CHI3L1), scavenger receptor cysteine-rich type 1 protein M130 (CD163) and osteoprotegerin, whereas PWV was associated with GDF15, E-selectin, CPA1, fatty acid-binding protein 4 (FABP4), CXCL16, carboxypeptidase B (CPB1), and tissue-type plasminogen activator. Upon entering ethnicity into the models, the associations between PWV and CPA1, CPB1, GDF-15, FABP4, CXCL16, and between cIMT and CCL-15, remained significant.Using a multiplex proteomic approach, we linked phenotypes of vascular health with several proteins. Novel associations were found between hypertension, PWV or cIMT and proteins linked to inflammatory response, chemotaxis, coagulation or proteolysis. Further, we could reveal whether the associations were ethnicity-dependent or not.

Renal Morphology in Coronavirus Disease: A Literature Review.

Renal biopsy is useful to better understand the histological pattern of a lesion (glomerular, tubulointerstitial, and vascular) and the pathogenesis that leads to kidney failure. The potential impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the kidneys is still undetermined, and a variety of lesions are seen in the kidney tissue of coronavirus disease patients. This review is based on the morphological findings of patients described in case reports and a series of published cases. A search was conducted on MEDLINE and PubMed of case reports and case series of lesions in the presence of non-critical infection by SARS-CoV-2 published until 15/09/2020. We highlight the potential of the virus directly influencing the damage or the innate and adaptive immune response activating cytokine and procoagulant cascades, in addition to the genetic component triggering glomerular diseases, mainly collapsing focal segmental glomerulosclerosis, tubulointerstitial, and even vascular diseases. Kidney lesions caused by SARS-CoV-2 are frequent and have an impact on morbidity and mortality; thus, studies are needed to assess the morphological kidney changes and their mechanisms and may help define their spectrum and immediate or long-term impact.

A possible role for HLA-G in development of uteroplacental acute atherosis in preeclampsia.

HLA-G, a non-classical HLA molecule expressed by extravillous trophoblasts, plays a role in the maternal immune tolerance towards fetal cells. HLA-G expression is regulated by genetic polymorphisms in the 3' untranslated region (3'UTR). Low levels of HLA-G in the maternal circulation and placental tissue are linked to preeclampsia. Our objective was to investigate whether variants of the 3'UTR of the HLA-G gene in mother and fetus are associated with acute atherosis, a pregnancy specific arterial lesion of the decidua basalis that is prevalent in preeclampsia. Paired maternal and fetal DNA samples from 83 normotensive and 83 preeclamptic pregnancies were analyzed. We sequenced the part of the HLA-G 3'UTR containing a 14-bp insertion/deletion region and seven single nucleotide polymorphisms (SNPs). Associations with acute atherosis were tested by logistic regression. The frequency of heterozygosity for the 14-bp polymorphism (Ins/Del) and the +3142 SNP (C/G) variant in the fetus are associated with acute atherosis in preeclampsia (66.7 % vs. 39.6 %, p = 0.039, and 69.0 % vs. 43.4 %, p = 0.024). Furthermore, the fetal UTR-3 haplotype, which encompasses the 14-bp deletion and the +3142G variant, is associated with acute atherosis in preeclampsia (15 % vs. 3.8 %, p = 0.016). In conclusion, HLA-G polymorphisms in the fetus are associated with acute atherosis. We hypothesize that these polymorphisms lead to altered HLA-G expression in the decidua basalis, affecting local feto-maternal immune tolerance and development of acute atherosis.

Expanding Phenotype of Schimke Immuno-Osseous Dysplasia: Congenital Anomalies of the Kidneys and of the Urinary Tract and Alteration of NK Cells.

Schimke immuno-osseous dysplasia (SIOD) is a rare multisystemic disorder with a variable clinical expressivity caused by biallelic variants in SMARCAL1. A phenotype-genotype correlation has been attempted and variable expressivity of biallelic SMARCAL1 variants may be associated with environmental and genetic disturbances of gene expression. We describe two siblings born from consanguineous parents with a diagnosis of SIOD revealed by whole exome sequencing (WES). Results: A homozygous missense variant in the SMARCAL1 gene (c.1682G>A; p.Arg561His) was identified in both patients. Despite carrying the same variant, the two patients showed substantial renal and immunological phenotypic differences. We describe features not previously associated with SIOD-both patients had congenital anomalies of the kidneys and of the urinary tract and one of them succumbed to a classical type congenital mesoblastic nephroma. We performed an extensive characterization of the immunophenotype showing combined immunodeficiency characterized by a profound lymphopenia, lack of thymic output, defective IL-7Rα expression, and disturbed B plasma cells differentiation and immunoglobulin production in addition to an altered NK-cell phenotype and function. Conclusions: Overall, our results contribute to extending the phenotypic spectrum of features associated with SMARCAL1 mutations and to better characterizing the underlying immunologic disorder with critical implications for therapeutic and management strategies.

Impact of Local Alloimmunity and Recipient Cells in Transplant Arteriosclerosis.

RATIONALE: Transplant arteriosclerosis is the major limitation to long-term survival of solid organ transplantation. Although both immune and nonimmune cells have been suggested to contribute to this process, the complex cellular heterogeneity within the grafts, and the underlying mechanisms regulating the disease progression remain largely uncharacterized. OBJECTIVE: We aimed to delineate the cellular heterogeneity within the allografts, and to explore possible mechanisms underlying this process. METHODS AND RESULTS: Here, we reported the transcriptional profiling of 11 868 cells in a mouse model of transplant arteriosclerosis by single-cell RNA sequencing. Unbiased clustering analyses identified 21 cell clusters at different stages of diseases, and focused analysis revealed several previously unknown subpopulations enriched in the allografts. Interestingly, we found evidence of the local formation of tertiary lymphoid tissues and suggested a possible local modulation of alloimmune responses within the grafts. Intercellular communication analyses uncovered a potential role of several ligands and receptors, including Ccl21a and Cxcr3, in regulating lymphatic endothelial cell-induced early chemotaxis and infiltration of immune cells. In vivo mouse experiments confirmed the therapeutic potential of CCL21 and CXCR3 neutralizing antibodies in transplant arteriosclerosis. Combinational use of genetic lineage tracing and single-cell techniques further indicate the infiltration of host-derived c-Kit+ stem cells as heterogeneous populations in the allografts. Finally, we compared the immune response between mouse allograft and atherosclerosis models in single-cell RNA-seq analysis. By analyzing susceptibility genes of disease traits, we also identified several cell clusters expressing genes associated with disease risk. CONCLUSIONS: Our study provides a transcriptional and cellular landscape of transplant arteriosclerosis, which could be fundamental to understanding the initiation and progression of this disease. CCL21/CXCR3 was also identified as important regulators of immune response and may serve as potential therapeutic targets in disease treatment.

Vascular Endothelial Cells and Innate Immunity.

In addition to the roles of endothelial cells (ECs) in physiological processes, ECs actively participate in both innate and adaptive immune responses. We previously reported that, in comparison to macrophages, a prototypic innate immune cell type, ECs have many innate immune functions that macrophages carry out, including cytokine secretion, phagocytic function, antigen presentation, pathogen-associated molecular patterns-, and danger-associated molecular patterns-sensing, proinflammatory, immune-enhancing, anti-inflammatory, immunosuppression, migration, heterogeneity, and plasticity. In this highlight, we introduce recent advances published in both ATVB and many other journals: (1) several significant characters classify ECs as novel immune cells not only in infections and allograft transplantation but also in metabolic diseases; (2) several new receptor systems including conditional danger-associated molecular pattern receptors, nonpattern receptors, and homeostasis associated molecular patterns receptors contribute to innate immune functions of ECs; (3) immunometabolism and innate immune memory determine the innate immune functions of ECs; (4) a great induction of the immune checkpoint receptors in ECs during inflammations suggests the immune tolerogenic functions of ECs; and (5) association of immune checkpoint inhibitors with cardiovascular adverse events and cardio-oncology indicates the potential contributions of ECs as innate immune cells.

Mfn2 inhibits chronic rejection of the rat abdominal aorta by regulating TGF-ß1 levels.

OBJECTIVES: The various forms of chronic rejection share a common histological appearance termed allograft arteriosclerosis. In the early stages thereof, apoptosis of vascular smooth muscle cells (VSMC) is obviously reduced, associated with vascular intimal thickening. High-level expression of the HSG/Mfn2 gene promotes apoptosis of rat VSMC. However, the role and mechanism of Mfn2 in inhibition of chronic allograft rejection have not been described. METHODS: In the present study, we transfected transplanted abdominal aortas of donor Lewis rats with an Mfn2-encoding or control lentivirus. And then We transplanted the donor aortas to the corresponding aortal positions in recipient rats. Transplanted aortas were collected on days 30, 60, and 90 and Masson stained to measure intimal thicknesses. Immunohistochemistry would be used to confirm TGF-ß1, Mfn2 and TGF-ß-R2 expression in different groups. RESULTS: Our results confirm that high-level expression of Mfn2 lowers the expression of TGF-ß1, reduces the intimal thickness of transplanted rat abdominal aorta, and retards the process of chronic rejection. CONCLUSION: Mfn2 influences TGF-ß/smad pathway and may function as potential chronic rejection inhibitor.

The Selective RNA Polymerase I Inhibitor CX-5461 Mitigates Neointimal Remodeling in a Modified Model of Rat Aortic Transplantation.

BACKGROUND: Transplant vasculopathy is a major cause of chronic rejection of transplanted organs. In the present study, we examined the effects of CX-5461, a novel selective inhibitor of RNA polymerase I, on development of transplant vasculopathy using a modified model of rat aortic transplantation. METHODS: The thoracic aortas from Fischer rats were transplanted into the abdominal cavity of Lewis rats. CX-5461 was mixed in pluronic gel and administered via perivascular release. RESULTS: Treatment with CX-5461 mitigated the development of neointimal hyperplasia and vascular inflammation. This effect was likely to be attributable in part to inhibition of macrophage-dependent innate immunity reactions. Specifically, CX-5461 exhibited potent inhibitory effects on macrophage migration and lipopolysaccharide-induced activation. Treatment with CX-5461 also prevented macrophage differentiation and maturation from primary bone marrow cells. In macrophages, CX-5461 did not alter the total amount of p53 protein, but significantly increased p53 phosphorylation, which was involved in regulating cytokine-stimulated macrophage proliferation. CONCLUSIONS: In conclusion, our results suggest that pharmacological inhibition of RNA polymerase I may be a novel strategy to treat transplantation-induced arterial remodeling.

Resveratrol alleviates lysophosphatidylcholine-induced damage and inflammation in vascular endothelial cells.

The role of resveratrol (trans-3,5,4'-trihydroxystilbene; RES) in lysophosphatidylcholine (LPC)­induced injury and inflammation in endothelial cells (regarded as an early event in arteriosclerosis) is unclear. The present study investigated whether RES reduces lactate dehydrogenase (LDH) activity and secretion of inflammatory cytokines such asinterleukin­6 and tumor necrosis factor­α, via the Toll­like receptor (TLR)­4/myeloid differentiation primary response gene 88 (MyD88)/nuclear factor (NF)­κB signal transduction pathway in LPC­induced damage and inflammation in human umbilical vein endothelial­12 (HUVE­12) cells. Using an ELISA and western blotting, the present study investigated the effects of RES on LDH activity and cytokine secretion. The effects of TLR­4 short hairpin (sh)RNA and TLR­4 cDNA transfection on NF­κB activation during LPC­induced damage and inflammation was also investigated in HUVE­12 cells. The results demonstrated that RES significantly inhibited the effect of LPC on enzyme activity, pro­inflammatory cytokine secretion, and expression of TLR­4, MyD88 and NF­κBp65 expression. In addition, RES and TLR­4 shRNA transfection suppressed LPC­induced injury and inflammation by blocking the TLR­4/MyD88/NF­κB signaling pathway Conversely, transfection with TLR­4 cDNA enhanced LPC­induced injury and inflammation, which abrogated the protective effects of RES. These data suggested that RES significantly suppressed LPC­induced damage and inflammation, via suppression of the TLR­4/MyD88/NF­κB signaling pathway, which may provide a new mechanistic evidence for the treatment of arteriosclerosis by RES.

A20 Haploinsufficiency Aggravates Transplant Arteriosclerosis in Mouse Vascular Allografts: Implications for Clinical Transplantation.

BACKGROUND: Inflammation is central to the pathogenesis of transplant arteriosclerosis (TA). We questioned whether physiologic levels of anti-inflammatory A20 influence TA severity. METHODS: We performed major histocompatibility complex mismatched aorta to carotid artery interposition grafts, using wild type (WT) or A20 heterozygote (HET) C57BL/6 (H-2) donors and BALB/c (H-2) recipients, and conversely BALB/c donors and WT/HET recipients. We analyzed aortic allografts by histology, immunohistochemistry, immunofluorescence, and gene profiling (quantitative real-time reverse-transcriptase polymerase chain reaction). We validated select in vivo A20 targets in human and mouse smooth muscle cell (SMC) cultures. RESULTS: We noted significantly greater intimal hyperplasia in HET versus WT allografts, indicating aggravated TA. Inadequate upregulation of A20 in HET allografts after transplantation was associated with excessive NF-кB activation, gauged by higher levels of IkBα, p65, VCAM-1, ICAM-1, CXCL10, CCL2, TNF, and IL-6 (mostly localized to SMC). Correspondingly, cytokine-induced upregulation of TNF and IL-6 in human and mouse SMC cultures inversely correlated with A20 expression. Aggravated TA in HET versus WT allografts correlated with increased intimal SMC proliferation, and a higher number of infiltrating IFNγ and Granzyme B CD4 T cells and natural killer cells, and lower number of FoxP3 regulatory T cells. A20 haploinsufficiency in allograft recipients did not influence TA. CONCLUSIONS: A20 haploinsufficiency in vascular allografts aggravates lesions of TA by exacerbating inflammation, SMC proliferation, and infiltration of pathogenic T cells. A20 single nucleotide polymorphisms associating with lower A20 expression or function in donors of vascularized allografts may inform risk and severity of TA, highlighting the clinical implications of our findings.

[Current status and future prospects in HMGB1 and receptor researches].

High mobility group box protein1 (HMGB1), a ubiquitous chromatin component, is released by necrotic cells, apoptotic cells, and cells in profound distress. HMGB1 plays a critical role as a proinflammatory mediator. HMGB1 represents an important new target for drug development in a variety of inflammatory disorders, including stroke, brain injury, arteriosclerosis, and cancer. The antibodies against HMGB1 and its receptors ar hopeful candidates for immunotherapeutic strategy for treating patients with these diseases. HMGB1 forms immunostimulatory complexes by interaction with cytokines and other endogenous or exogenous factors. The HMGB1-partner molecule complexes can enhance the immune response induced by the ligand alone. The current status of HMGB1 works is summarized and future prospects will be provided in this review.

Malondialdehyde Epitopes as Targets of Immunity and the Implications for Atherosclerosis.

Accumulating evidence suggests that oxidation-specific epitopes (OSEs) constitute a novel class of damage-associated molecular patterns (DAMPs) generated during high oxidative stress but also in the physiological process of apoptosis. To deal with the potentially harmful consequences of such epitopes, the immune system has developed several mechanisms to protect from OSEs and to orchestrate their clearance, including IgM natural antibodies and both cellular- and membrane-bound receptors. Here, we focus on malondialdehyde (MDA) epitopes as prominent examples of OSEs that trigger both innate and adaptive immune responses. First, we review the mechanisms of MDA generation, the different types of adducts on various biomolecules and provide relevant examples for physiological carriers of MDA such as apoptotic cells, microvesicles, or oxidized low-density lipoproteins. Based on recent insights, we argue that MDA epitopes contribute to the maintenance of homeostatic functions by acting as markers of elevated oxidative stress and tissue damage. We discuss multiple lines of evidence that MDA epitopes are proinflammatory and thus important targets of innate and adaptive immune responses. Finally, we illustrate the relevance of MDA epitopes in human pathologies by describing their capacity to drive inflammatory processes in atherosclerosis and highlighting protective mechanisms of immunity that could be exploited for therapeutic purposes.

Characteristics of the peripheral T cell immune response of patients at different stages of vascular cognitive impairment.

AIM: To investigate the characteristics of the peripheral T cell immune response of patients at different stages of vascular cognitive impairment (VCI). METHODS: 61 Arterial atherosclerotic cerebral infarct induced VCI patients, including 28 vascular dementia (VaD) cases, 33 no dementia (VCI-ND) cases, and 25 atherosclerotic cerebral infarct patients with normal cognitive function (CI-NC) as controls were enrolled. Peripheral CD8(+)T, CD4(+)CD25(+) Treg, CD4(+)IL-17(+) Th17 cells proportion, and IL-1ß, IL-2, IL-6, IFN-γ levels, and neuropsychological function were assessed. RESULTS: There was no difference in average age, gender ratio, years of education, and risk factors of infarct among the three groups. Peripheral CD4(+)CD25(+) Treg in VCI-ND and VaD groups were significantly lower than that in controls, and CD8(+) T cells were markedly elevated in VaD group. The IL-17(+) Th17 cell proportion did not differ significantly among three groups. IL-6 and IFN-γ expression levels in VaD group were higher than those in other two groups. The VDAS-Cog executive function subscale score was negatively correlated with CD4(+)CD25(+) Treg proportion in VCI patients, and positively correlated with IL-6 levels. CONCLUSION: VCI patients demonstrated a decrease in peripheral CD4(+) Treg proportion and increased IL-6 expression, and both parameters were correlated with the decline of executive functions.

Mouse model of alloimmune-induced vascular rejection and transplant arteriosclerosis.

Vascular rejection that leads to transplant arteriosclerosis (TA) is the leading representation of chronic heart transplant failure. In TA, the immune system of the recipient causes damage of the arterial wall and dysfunction of endothelial cells and smooth muscle cells. This triggers a pathological repair response that is characterized by intimal thickening and luminal occlusion. Understanding the mechanisms by which the immune system causes vasculature rejection and TA may inform the development of novel ways to manage graft failure. Here, we describe a mouse aortic interposition model that can be used to study the pathogenic mechanisms of vascular rejection and TA. The model involves grafting of an aortic segment from a donor animal into an allogeneic recipient. Rejection of the artery segment involves alloimmune reactions and results in arterial changes that resemble vascular rejection. The basic technical approach we describe can be used with different mouse strains and targeted interventions to answer specific questions related to vascular rejection and TA.

Physical exercise reduces transplant arteriosclerosis in a mouse aorta transplantation model.

BACKGROUND: Transplant arteriosclerosis limits long-term outcome after heart transplantation. The underlying mechanism of transplant arteriosclerosis remains alloreactivity, but it is also influenced by nonimmunologic cofactors. Physical exercise has well-established effects on the prevention of native arteriosclerosis. We hypothesized that physical exercise would reduce the development of transplant arteriosclerosis in an allogeneic transplantation setting. METHODS: Segments of the thoracic aorta from C57.Bl6 (H2b) or C3H.HeJ (H2k) mice were transplanted into the abdominal aortas of CBA.Ca mice (H2k), representing a major or minor alloantigen mismatch, respectively. Three days after surgery, recipient mice were assigned to either the control or physical exercise (consisting of 2 × 45 minutes of treadmill training per day) groups. Transplant arteriosclerosis was assessed and quantified by histology on day 28 after vessel transplantation. Endothelial cell integrity and function in histology sections and peripheral blood was assessed. RESULTS: All animals developed transplant arteriosclerosis with more severe luminal occlusion in the major alloantigen mismatch setting. Animals undergoing physical exercise developed significantly less severe transplant arteriosclerosis in both the major (P < .0001) and minor (P < .0001) antigen mismatches than their respective control groups without physical exercise. CD31(+) endothelial cells were present in significantly higher numbers in the grafts and circulating in peripheral blood in the exercise groups compared with their respective control. Above that, we found enhanced endothelial nitric oxide synthase-positive cells in both exercise groups compared with the untreated groups (P = .01 and P = .02, respectively). CONCLUSIONS: Physical exercise has a protective effect against the development of transplant arteriosclerosis. This could be due to enhanced endothelial cell regeneration and function in the graft.

The multiple faces of CCL13 in immunity and inflammation.

CCL13/MCP-4, is a CC family chemokine that is chemoattractant for eosinophils, basophils, monocytes, macrophages, immature dendritic cells, and T cells, and its capable of inducing crucial immuno-modulatory responses through its effects on epithelial, muscular and endothelial cells. Similar to other CC chemokines, CCL13 binds to several chemokine receptors (CCR1, CCR2 and CCR3), allowing it to elicit different effects on its target cells. A number of studies have shown that CCL13 is involved in many chronic inflammatory diseases, in which it functions as a pivotal molecule involved in the selective recruitment of cell lineages to the inflamed tissues and their subsequent activation. Based on these studies, we suggest that blocking the actions of CCL13 can serve as a novel strategy for the generation of agents with anti-inflammatory activity. The main goal of this review is to present the current information about CCL13, its gene and protein structure and the roles of this chemokine during innate/adaptive immune responses in inflammatory diseases.

Prostaglandin E2 potentiates mesenchymal stem cell-induced IL-10+IFN-γ+CD4+ regulatory T cells to control transplant arteriosclerosis.

Mesenchymal stem cells (MSCs) are known for their immunomodulatory functions. We previously demonstrated that bone marrow-derived MSCs effectively control transplant arteriosclerosis (TA) by enhancing IL-10(+) and IFN-γ(+) cells. The objective of this study is to elucidate the mechanism by which MSCs induce IL-10(+)IFN-γ(+)CD4(+) regulatory T type 1 (T(R)1)-like cells. In an MLR system using porcine PBMCs, MSC-induced IL-10(+)IFN-γ(+)CD4(+) cells, which confer resistance to allogeneic proliferation in an IL-10-dependent manner, resemble T(R)1-like cells. Both cyclooxygenase-derived PGE(2) and IDO help to induce T(R)1-like cells by MSCs. MSCs constitutively secrete PGE(2), which is augmented in allogeneic reactions. However, T(R)1-like cells were deficient in PGE(2) and 4-fold less potent than were MSCs in suppressing MLR. PGE(2) mimetic supplements can enhance the immunosuppressive potency of T(R)1-like cells. In a porcine model of allogeneic femoral arterial transplantation, MSC-induced T(R)1-like cells combined with PGE(2), but not either alone, significantly reduced TA at the end of 6 wk (percentage of luminal area stenosis: T(R)1-like cells + PGE(2): 11 ± 10%; PGE(2) alone: 93 ± 8.7%; T(R)1-like cells alone: 88 ± 2.4% versus untreated 94 ± 0.9%, p < 0.001). These findings indicate that PGE(2) helps MSC-induced IL-10(+)IFN-γ(+)CD4(+) T(R)1-like cells inhibit TA. PGE(2) combined with MSC-induced T(R)1-like cells represents a new approach for achieving immune tolerance.

Inflammatory Ly-6C(hi) monocytes play an important role in the development of severe transplant arteriosclerosis in hyperlipidemic recipients.

OBJECTIVE: Transplant arteriosclerosis (TA) restricts long-term survival of heart transplant recipients. Although the role of monocyte/macrophages is well established in native atherosclerosis, it has been studied to a much lesser extent in TA. Plasma cholesterol is the most important non-immunologic risk factor for development of TA but the underlying mechanisms are largely unknown. We hypothesized that monocyte/macrophages might play an important role in the pathogenesis of TA under hyperlipidemic conditions. METHODS: We studied TA in fully mismatched arterial allografts transplanted into hyperlipidemic ApoE(-/-) recipients compared to wild-type controls. The recruitment of distinct monocyte populations into the grafts was tracked by in vivo labelling with fluorescent microspheres. We used antibody-mediated depletion protocols to dissect the relative contribution of T lymphocytes and monocytes to disease development. RESULTS: In the hyperlipidemic environment the progression of TA was highly exacerbated and the inflammatory CD11b(+)CD115(+)Ly-6C(hi) monocytes were preferentially recruited into the neointima. The number of macrophage-derived foam cells present in the grafts strongly correlated with plasma cholesterol and disease severity. Depletion of Ly-6C(hi) monocytes and neutrophils significantly inhibited macrophage accumulation and disease progression. The accelerated monocyte recruitment occurs through a T cell-independent mechanism, as T cell depletion did not influence macrophage accumulation into the grafts. CONCLUSIONS: Our study identifies for the first time the involvement of inflammatory Ly-6C(hi) monocytes into the pathogenesis of TA, particularly in conditions of hyperlipidemia. Targeted therapies modulating the recruitment and activation of these cells could potentially delay coronary allograft vasculopathy and improve long-term survival of heart transplant recipients.