The biliary epithelium presents antigens to and activates natural killer T cells

Cholangiocytes express antigen-presenting molecules, but it has been unclear whether they can present antigens. Natural killer T (NKT) cells respond to lipid antigens presented by the major histocompatibility complex class I-like molecule CD1d and are abundant in the liver. We investigated whether cholangiocytes express CD1d and present lipid antigens to NKT cells and how CD1d expression varies in healthy and diseased bile ducts. Murine and human cholangiocyte cell lines as well as human primary cholangiocytes expressed CD1d as determined by flow cytometry and western blotting. Murine cholangiocyte cell lines were able to present both exogenous and endogenous lipid antigens to invariant and noninvariant NKT cell hybridomas and primary NKT cells in a CD1d-dependent manner. A human cholangiocyte cell line, cholangiocarcinoma cell lines, and human primary cholangiocytes also presented exogenous CD1d-restricted antigens to invariant NKT cell clones. CD1d expression was down-regulated in the biliary epithelium of patients with late primary sclerosing cholangitis, primary biliary cirrhosis, and alcoholic cirrhosis compared to healthy controls.

CONCLUSIONS

Cholangiocytes express CD1d and present antigens to NKT cells and CD1d expression is down-regulated in diseased biliary epithelium, findings which show that the biliary epithelium can activate an important lymphocyte subset of the liver. This is a potentially important immune pathway in the biliary system, which may be capable of regulating inflammation in the context of biliary disease.

Oligomerized, filamentous surface presentation of RANTES/CCL5 on vascular endothelial cells

Vascular endothelial cells present luminal chemokines that arrest rolling leukocytes by activating integrins. It appears that several chemokines must form higher-order oligomers to elicit proper in vivo effects, as mutants restricted to forming dimers have lost the ability to recruit leukocytes to sites of inflammation. Here, we show for the first time that the chemokine RANTES/CCL5 binds to the surface of human endothelial cells in a regular filamentous pattern. Furthermore, the filaments bound to the surface in a heparan sulfate-dependent manner. By electron microscopy we observed labeling for RANTES on membrane projections as well as on the remaining plasma membrane. Mutant constructs of RANTES restricted either in binding to heparin, or in forming dimers or tetramers, appeared either in a granular, non-filamentous pattern or were not detectable on the cell surface. The RANTES filaments were also present after exposure to flow, suggesting that they can be present in vivo. Taken together with the lacking in vivo or in vitro effects of RANTES mutants, we suggest that the filamentous structures of RANTES may be of physiological importance in leukocyte recruitment.

Expression of the T cell-specific adapter protein in human tissues

T cell-specific adapter protein (TSAd) encoded by the SH2D2A gene is expressed in activated T cells, NK cells and endothelial cells, but its tissue expression has not yet been mapped. Here, we have defined the specificity of two commercially available anti-TSAd monoclonal reagents using peptide arrays. We found them to bind separate epitopes in the C-terminal part of TSAd. We then used immunohistochemistry to examine TSAd expression in various human lymphoid and non-lymphoid tissues. Immunostaining of adjacent tissue sections revealed that a substantial fraction of CD3-positive cells in normal lymphoid and non-lymphoid tissues expressed TSAd. In particular, essentially all intra-epithelial T cells appeared to coexpress TSAd. In addition, TSAd expression was observed in endothelial cells of dermal microvessels, while it was not detected in endothelial cells of the other tested tissues. This work provides insight into the expression pattern of TSAd in various healthy human tissues.

Generation and characterization of an immortalized human mesenchymal stromal cell line

Human mesenchymal stromal cells (hMSCs) show great potential for clinical and experimental use due to their capacity to self-renew and differentiate into multiple mesenchymal lineages. However, disadvantages of primary cultures of hMSCs are the limited in vitro lifespan, and the variable properties of cells from different donors and over time in culture. In this article, we describe the generation of a telomerase-immortalized nontumorigenic human bone marrow-derived stromal mesenchymal cell line, and its detailed characterization after long-term culturing (up to 155 population doublings). The resulting cell line, iMSC#3, maintained a fibroblast-like phenotype comparable to early passages of primary hMSCs, and showed no major differences from hMSCs regarding surface marker expression. Furthermore, iMSC#3 had a normal karyotype, and high-resolution array comparative genomic hybridization confirmed normal copy numbers. The gene expression profiles of immortalized and primary hMSCs were also similar, whereas the corresponding DNA methylation profiles were more diverse. The cells also had proliferation characteristics comparable to primary hMSCs and maintained the capacity to differentiate into osteoblasts and adipocytes. A detailed characterization of the mRNA and microRNA transcriptomes during adipocyte differentiation also showed that the iMSC#3 recapitulates this process at the molecular level. In summary, the immortalized mesenchymal cells represent a valuable model system that can be used for studies of candidate genes and their role in differentiation or oncogenic transformation, and basic studies of mesenchymal biology.

Indirect CD4+ T-cell-mediated elimination of MHC II(NEG) tumor cells is spatially restricted and fails to prevent escape of antigen-negative cells

Tumor-specific Th1 cells can activate tumor-infiltrating macrophages that eliminate MHC class II negative (MHC II(NEG)) tumor cells. Activated M1-like macrophages lack antigen (Ag) receptors, and are presumably unable to discriminate and thus kill both Ag-positive (Ag(POS)) and Ag-negative (Ag(NEG)) tumor cells (bystander killing). The lack of specificity of macrophage-mediated cytotoxicity might be of clinical importance as it could provide a means of avoiding tumor escape. Here, we have tested this idea using mixed populations of Ag(POS) and Ag(NEG) tumor cells in a TCR-transgenic model in which CD4(+) T cells recognize a secreted tumor-specific antigen. Surprisingly, while Ag(POS) tumor cells were recognized and rejected, Ag(NEG) cells grew unimpeded and formed tumors. We further demonstrated that macrophage-mediated cytotoxicity was spatially restricted to areas dominated by Ag(POS) tumor cells, sparing Ag(NEG) tumor cells in the vicinity. As a consequence, macrophage tumoricidal activity did not confer bystander killing in vivo. The present results offer novel insight into the mechanisms of indirect Th1-mediated elimination of MHC II(NEG) tumor cells.

Cellular expression of the alarmin IL-33 in acute skin inflammation (P6337)

Background: IL-33, a recently described member of the IL-1-family, is an important player in a variety of inflammatory settings and is thought to be released from damaged or necrotic cells. Little work has so far been published on the cellular expression and regulation of IL-33 in inflammatory lesions. Results: In normal mouse skin IL-33 showed a nuclear expression in non-proliferating keratinocytes (Ki67-) and periglandular myoepithelial cells. After injection with Staphylococcus aureus (6h i.d.) we observed that nuclear IL-33 disappeared from keratinocytes in the center of the lesion and instead appeared in fibroblasts at the periphery. The keratinocyte layer remained intact and expressed nuclear HMGB1, revealing no evidence of overt necrosis at this time point, thus indicating possible secretion. Wound lesions of the ear showed a similar picture at the margins. At later time points IL-33 reappeared in keratinocytes, initially in a hyperproliferative, multilayer structure in which IL33 and Ki-67 remained minimally co-localized. Similarly, in cultured human keratinocytes there was constitutive expression of nuclear IL-33 in non-proliferating cells and in contrast to endothelial cells, expression levels appeared unaffected by cell density or pro-inflammatory activation (TNF-a or IL1b) Conclusion: The regulation of IL-33 in keratinocytes appears to involve molecular signals different from the regulation seen in vascular endothelial cells and deserves further investigation.

CD4+ T cell-mediated protection against tumors: no bystander killing (P2114)

Background: MHC class II-restricted CD4+ T cells reactive against the Id peptide of MHC class II-negative MOPC315 murine myeloma cells can protect mice against injected tumors. This protection occurs via indirect recognition of secreted tumor-specific antigen, presented on MHC class II-molecules of tumor-infiltrating CD11b+ cells. Activated Id-specific Th1 cells produce IFNγ that activate macrophages which become cytotoxic to tumor cells. We wanted to assay the ability of such CD4+/M1 macrophage mediated protection to prevent the outgrowth of antigen-loss tumor variants. Methods: Id-specific TCR-transgenic SCID mice were challenged with a mixed population of Id-secreting and non-secreting MOPC315 cells, differentially labeled with fluorescent proteins. Tumor growth was monitored by in vivo imaging. Tumor-infiltrating macrophages were assayed for their ability to inhibit tumor growth. Results: In the presence of a large excess of antigen-secreting tumor cells, outgrowth of antigen loss-variants occurred with no evidence of bystander killing. A predominance of alternatively activated macrophages was seen in areas dominated by antigen loss-variants, whereas classic activation was the dominant phenotype in areas populated by regressing Id-secreting tumor cells. In vitro, growth of antigen loss-variants was completely inhibited by the provision of the tumor-specific antigen. This data suggests strict spatial requirements of antigen for effective macrophage-mediated protection.

The alarmin IL-33 is a notch target in quiescent endothelial cells

The molecular mechanisms that drive expression of the alarmin interleukin-33 (IL-33) in endothelial cells are unknown. Because nuclear IL-33 is a marker of endothelial cell quiescence (corroborated in this study by coexpression of cyclin-dependent kinase inhibitor p27(Kip1)), we hypothesized that Notch signaling might be involved in regulating IL-33 expression. Activation of Notch1 by immobilized Notch ligands was sufficient to induce nuclear IL-33 expression in cultured endothelial cells. Conversely, IL-33 expression was inhibited by the γ-secretase inhibitor DAPT or by inhibiting the function of Dll4, Jagged1, Notch1, or the canonical Notch transcription factor RBP-Jκ. Insensitivity to cycloheximide indicated that IL-33 was a direct target of Notch signaling, well in line with the identification of several conserved RBP-Jκ binding sites in the IL33 gene. The in vivo expression of Dll4 but not of Jagged1 was well correlated with expression of IL-33 in quiescent vessels, and subcutaneous injection of DAPT in healthy skin reduced IL-33 expression, indicating that Notch signaling was involved. On the other hand, loss of IL-33 during angiogenesis occurred despite sustained Dll4 and Notch1 expression, suggesting that other signals may override the IL-33-driving signal in this context. Taken together, our data demonstrate that endothelial nuclear IL-33 is induced by Notch and that Dll4 may be the dominant ligand responsible for this signaling in vivo.

Statins affect the presentation of endothelial chemokines by targeting to multivesicular bodies

Background

In addition to lowering cholesterol, statins are thought to beneficially modulate inflammation. Several chemokines including CXCL1/growth-related oncogene (GRO)-α, CXCL8/interleukin (IL)-8 and CCL2/monocyte chemoattractant protein (MCP)-1 are important in the pathogenesis of atherosclerosis and can be influenced by statin-treatment. Recently, we observed that atorvastatin­treatment alters the intracellular content and subcellular distribution of GRO-α in cultured human umbilical vein endothelial cells (HUVECs). The objective of this study was to investigate the mechanisms involved in this phenomenon.

Methodology/ Principal Findings

The effect of atorvastatin on secretion levels and subcellular distribution of GRO-α, IL-8 and MCP-1 in HUVECs activated by interleukin (IL)-1β were evaluated by ELISA, confocal microscopy and immunoelectron microscopy. Atorvastatin increased the intracellular contents of GRO-α, IL-8, and MCP-1 and induced colocalization with E-selectin in multivesicular bodies. This effect was prevented by adding the isoprenylation substrate GGPP, but not the cholesterol precursor squalene, indicating that atorvastatin exerts these effects by inhibiting isoprenylation rather than depleting the cells of cholesterol.

Conclusions/ Significance

Atorvastatin targets inflammatory chemokines to the endocytic pathway and multivesicular bodies and may contribute to explain the anti-inflammatory effect of statins at the level of endothelial cell function.

The Alarmin Interleukin-33 is a Notch Target in Quiescent Endothelial Cells (174.6)

The molecular mechanisms that induce and maintain expression of the alarming interleukin-33 (IL-33) in endothelial cells are unknown. Based on the observation that IL-33 is also a marker of endothelial cell quiescence, we hypothesized that the Notch signaling pathway might be involved in regulation of IL-33 expression. Here we show that activation of Notch1 by immobilized Notch ligands was sufficient to induce nuclear IL-33 expression in human umbilical vein endothelial cells (HUVECs). Furthermore, IL-33 expression in confluent HUVECs was inhibited by the γ-secretase inhibitor DAPT or by blocking antibodies to Dll4, Jagged1 or Notch1, as well as by knockdown of the transcription factor RBP-Jκ. In vivo, expression of Dll4 but not Jagged1 was generally observed in all segments of quiescent vessels in healthy organs in both human and rat tissue, and therefore well correlated with expression of IL-33. Moreover, subcutaneous injections of DAPT markedly reduced expression of vascular IL-33, compatible with a role for Notch signaling in driving vascular IL-33 expression in vivo. Taken together, our data demonstrate that the alarmin IL-33 is a target of Notch and serve to further establish Notch signaling in innate immune defense.

Endostatin suppresses IGF-II-mediated signaling and invasion of human extravillous trophoblasts

Endostatin, a biological active fragment of the extracellular matrix protein collagen XVIII, is known to interfere with cellular motility in the context of pathological angiogenesis. However, the physiological role of endostatin remains largely elusive. Recent evidence suggested that the inhibitor is produced in human decidual cells of early pregnancy, indicating that endostatin could be involved in diverse reproductive processes, such as implantation and/or placental differentiation. To gain more insights into the role of endostatin, we here analyzed its effects on trophoblast motility, proliferation, and signaling using purified primary trophoblasts, first-trimester villous explant cultures, and trophoblastic SGHPL-5 cells. In vitro Transwell assays demonstrated that purified endostatin inhibited both basal and IGF-II-induced migration and invasion as well as outgrowth from villous explant cultures. In contrast, basal and IGF-II-stimulated proliferation was unaffected upon addition of the inhibitor. Analyses of IGF-II-associated downstream signaling events showed that endostatin interfered with activation of various signaling kinases such as ERK1/2, protein kinase B (Akt)/mammalian target of rapamycin/p70 S6 kinase, and focal adhesion kinase. Furthermore, virus-mediated, stable gene silencing of Akt1 in SGHPL-5 cells using a micro-RNA-adapted short hairpin RNA-expressing plasmid revealed that endostatin-mediated inhibition of IGF-II-induced Akt phosphorylation was critically dependent on the expression of the particular isoform. In conclusion, the data suggest that endostatin could be a physiological inhibitor of IGF-II-dependent trophoblast cell motility by suppressing focal adhesion kinase/Akt/mammalian target of rapamycin/p70 S6 kinase signaling.

Inflammatory bowel disease-associated interleukin-33 is preferentially expressed in ulceration-associated myofibroblasts

Interleukin-33 (IL-33) is a novel member of the interleukin-1 family that induces mucosal pathology in vivo and may drive fibrosis development and angiogenesis. To address its potential role in inflammatory bowel disease, we explored its tissue expression in biopsy specimens from untreated ulcerative colitis patients, observing a 2.6-fold up-regulation of IL-33 mRNA levels, compared to controls. Immunohistochemical analyses of surgical specimens showed that a prominent source of IL-33 in ulcerative colitis lesions were ulceration-associated myofibroblasts that co-expressed the fibroblast marker heat shock protein 47, platelet-derived growth factor receptor (PDGFR)β, and, in part, the myofibroblast marker α-smooth muscle actin (SMA). In contrast, IL-33-positive myofibroblasts were almost absent near the deep fissures seen in Crohn's disease. A screen of known and putative activators of IL-33 in cultured fibroblasts revealed that the Toll-like receptor-3 agonist poly (I:C) was among the strongest inducers of IL-33 and that it synergized with transforming growth factor-β, a combination also known to boost myofibroblast differentiation. Experimental wound healing in rat skin revealed that the de novo induction of IL-33 in pericytes and the possible activation of scattered, tissue-resident IL-33(+)PDGFRβ(+)αSMA(-) fibroblast-like cells were early events that preceded the later appearance of IL-33(+)PDGFRβ(+)αSMA(+) cells. In conclusion, our data point to a novel role for IL-33 in mucosal healing and wound repair and to an interesting difference between ulcerative colitis and Crohn's disease.

Genome-wide transcription profile of endothelial cells after cardiac transplantation in the rat

Transcriptome analyses of organ transplants have until now usually focused on whole tissue samples containing activation profiles from different cell populations. Here, we enriched endothelial cells from rat cardiac allografts and isografts, establishing their activation profile at baseline and on days 2, 3 and 4 after transplantation. Modulated transcripts were assigned to three categories based on their regulation profile in allografts and isografts. Categories A and B contained the majority of transcripts and showed similar regulation in both graft types, appearing to represent responses to surgical trauma. By contrast, category C contained transcripts that were partly allograft-specific and to a large extent associated with interferon-gamma-responsiveness. Several transcripts were verified by immunohistochemical analysis of graft lesions, among them the matricellular protein periostin, which was one of the most highly upregulated transcripts but has not been associated with transplantation previously. In conclusion, the majority of the differentially expressed genes in graft endothelial cells are affected by the transplantation procedure whereas relatively few are associated with allograft rejection.

The murine IL-8 homologues KC, MIP-2, and LIX are found in endothelial cytoplasmic granules but not in Weibel-Palade bodies

Rapid translocation of P-selectin from WPB to the surface of endothelial cells is crucial for early neutrophil recruitment to acute inflammatory lesions. Likewise, the chemokine CXCL8/IL-8 is sorted to WPB in human endothelial cells, but little is known about its functional importance in lack of a suitable animal model. Here, we explored the distribution of the functional IL-8 homologues CXCL1/KC, CXCL2/MIP-2, and CXCL5-6/LIX in resting and inflamed murine vessels by confocal microscopy and paired immunostaining with markers of WPB, discovering that these chemokines did not localize to WPB but displayed a granular pattern in a subset of vessels in healthy skin compatible with sorting to the type 2 endothelial compartment for regulated secretion. Moreover, all chemokines colocalized with VWF and P-selectin in platelets, suggesting that their storage in platelet alpha-granules might represent an alternative source of rapidly available, neutrophil-recruiting chemokines. In conclusion, WPB appear not to be involved in regulated secretion of chemokines in the mouse, and instead, the possible existence of type 2 granules and the role of platelets in rapid leukocyte adhesion deserve further attention.

Family-with-sequence-similarity-46, member A (Fam46a) gene is expressed in developing tooth buds

OBJECTIVE

In search for possible novel genes that may be involved in tooth development, we analysed the genome-wide transcriptome of developing mandibular tooth germs of mouse during embryonic and early life and selected family-with-sequence-similarity-46, member A (Fam46a) gene for further expression analysis.

METHODS

We applied microarray, quantitative real time polymerase chain reaction and in situ hybridisation methods for the expression study of the mouse Fam46a gene.

RESULTS

We found the family-with-sequence-similarity-46, member A (Fam46a) gene to be highly expressed and further verify its temporo-spatial expression in the mouse tooth.

CONCLUSION

We have shown that Fam46a is expressed in ameloblasts' nuclei of tooth germs and hypothesise that it might act together with morphogenetic factors important for the formation of enamel in mouse tooth.

Molecular requirements for sorting of the chemokine interleukin-8/CXCL8 to endothelial Weibel-Palade bodies

Sorting of proteins to Weibel-Palade bodies (WPB) of endothelial cells allows rapid regulated secretion of leukocyte-recruiting P-selectin and chemokines as well as procoagulant von Willebrand factor (VWF). Here we show by domain swap studies that the exposed aspartic acid in loop 2 (Ser(44)-Asp(45)-Gly(46)) of the CXC chemokine interleukin (IL)-8 is crucial for targeting to WPB. Loop 2 also governs sorting of chemokines to alpha-granules of platelets, but the fingerprint of the loop 2 of these chemokines differs from that of IL-8. On the other hand, loop 2 of IL-8 closely resembles a surface-exposed sequence of the VWF propeptide, the region of VWF that directs sorting of the protein to WPB. We conclude that loop 2 of IL-8 constitutes a critical signal for sorting to WPB and propose a general role for this loop in the sorting of chemokines to compartments of regulated secretion.

Interleukin-33 - cytokine of dual function or novel alarmin?

Cytokines are thought to exert biological effects through their specific cell surface membrane receptors but increasing evidence suggests that some also function within the nucleus. Here, we review current knowledge of such cytokines, including the novel interleukin (IL)-1 family member IL-33. Its extracellular function has attracted much recent attention as a ligand for the Th2-associated ST2 receptor, but the discoveries of its nuclear functions and modes of secretion are only just beginning to surface. We review the currently available data on IL-33 regulation, nuclear function and release and discuss them in the context of other intranuclear cytokines and the prototype alarmin HMGB1, considering to what extent IL-33 can be seen as a novel member of the alarmin family.

Nuclear interleukin-33 is generally expressed in resting endothelium but rapidly lost upon angiogenic or proinflammatory activation

Interleukin (IL)-33 is a novel member of the IL-1 family of cytokines that promotes Th2 responses in lymphocytes as well as the activation of both mast cells and eosinophils via the ST2 receptor. Additionally, IL-33 has been proposed to act as a chromatin-associated transcriptional regulator in both endothelial cells of high endothelial venules and chronically inflamed vessels. Here we show that nuclear IL-33 is expressed in blood vessels of healthy tissues but down-regulated at the earliest onset of angiogenesis during wound healing; in addition, it is almost undetectable in human tumor vessels. Accordingly, IL-33 is induced when cultured endothelial cells reach confluence and stop proliferating but is lost when these cells begin to migrate. However, IL-33 expression was not induced by inhibiting cell cycle progression in subconfluent cultures and was not prevented by antibody-mediated inhibition of VE-cadherin. Conversely, IL-33 knockdown did not induce detectable changes in either expression levels or the cellular distribution of either VE-cadherin or CD31. However, activation of endothelial cell cultures with either tumor necrosis factor-alpha or vascular endothelial growth factor and subcutaneous injection of these cytokines led to a down-regulation of vascular IL-33, a response consistent with both its rapid down-regulation in wound healing and loss in tumor endothelium. In conclusion, we speculate that the proposed transcriptional repressor function of IL-33 may be involved in the control of endothelial cell activation.

Cytokine secretion depends on Galalpha(1,3)Gal expression in a pig-to-human whole blood model

Transplants from alpha1,3-galactosyltransferase (Gal) gene-knockout pigs to nonhuman primates are largely protected from hyperacute but not acute humoral xenograft rejection. The present study investigates the role of Gal in cytokine responses using a novel pig-to-human whole blood in vitro model, developed for species-specific analysis of porcine and human cytokines. Porcine (n = 7) and human (n = 27) cytokines were measured using ELISA or multiplex technology, respectively. Porcine aortic endothelial cells from control (Gal(+/+)) and Gal-deficient (Gal(-/-)) pigs were incubated with human lepirudin anticoagulated whole blood from healthy donors. E-selectin expression was measured by flow cytometry. The C3 inhibitor compstatin and a C5aR antagonist were used to study the role of complement. Cytokine species specificity was documented, enabling detection of 2 of 7 porcine cytokines and 13 of 27 human cytokines in one single sample. Gal(+/+) porcine aortic endothelial cells incubated with human whole blood showed a marked complement C5b-9 dependent up-regulation of E-selectin and secretion of porcine IL-6 and IL-8. In contrast, Gal(-/-) cells responded with E-selectin and cytokine expression which was so weak that the role of complement could not be determined. Human IL-6, IL-8, IFN-gamma, MIP-1alpha, MIP-1beta, eotaxin, and RANTES were detected in the Gal(+/+) system, but virtually no responses were seen in the Gal(-/-) system (p = 0.03). The increase in human cytokine release was largely complement dependent and, in contrast to the porcine response, mediated through C5a. Species-specific analysis of cytokine release revealed a marked, complement-dependent response when Gal(+/+) pig cells were incubated with human whole blood, compared with Gal(-/-) cells which induced virtually no cytokine release.

A potential role of the CXC chemokine GROalpha in atherosclerosis and plaque destabilization: downregulatory effects of statins

OBJECTIVE

We examined the role of the CXCR2 ligand growth-related oncogene (GRO) alpha in human atherosclerosis.

METHODS AND RESULTS

GROalpha levels were examined by enzyme immunoassay, real-time quantitative RT-PCR, and cDNA microarrays. The in vitro effect of statins on GROalpha was examined in endothelial cells and THP-1 macrophages. Our main findings were: (1) GROalpha was among the 10 most differentially expressed transcripts comparing peripheral blood mononuclear cells (PBMCs) from patients with coronary artery disease (CAD) and healthy controls. (2) Both patients with stable (n=41) and particularly those with unstable (n=47) angina had increased plasma levels of GROalpha comparing controls (n=20). (3) We found increased expression of GROalpha within symptomatic carotid plaques, located to macrophages and endothelial cells. (4) GROalpha enhanced the release of matrix metalloproteinases in vascular smooth muscle cells, and increased the binding of acetylated LDL in macrophages. (5) Atorvastatin downregulated GROalpha levels as shown both in vitro in endothelial cells and macrophages and in vivo in PBMCs from CAD patients. (6) The effect on GROalpha in endothelial cells involved increased storage and reduced secretion of GROalpha.

CONCLUSIONS

GROalpha could be involved in atherogenesis and plaque destabilization, potentially contributing to inflammation, matrix degradation, and lipid accumulation within the atherosclerotic lesion.

The HUVEC/Matrigel assay: an in vivo assay of human angiogenesis suitable for drug validation

The future ability to manipulate the growth of new blood vessels (angiogenesis) holds great promise for treating ischemic disease and cancer. Several models of human in vivo angiogenesis have been described, but they seem to depend on transgenic support and have not been validated in a therapeutic context. Here, we describe an in vivo assay that mimics human angiogenesis in which native human umbilical vein-derived endothelial cells are suspended in a liquid laminin/collagen gel (Matrigel), injected into immunodeficient mice, and develop into mature, functional vessels that vascularize the Matrigel plug in the course of 30 d. Moreover, we demonstrate how to target this process therapeutically by sustained delivery of the angiogenesis inhibitor endostatin from subcutaneously implanted microosmotic pumps.

Human complement-activating immunoglobulin (Ig)G3 antibodies are essential for porcine endothelial cell activation

BACKGROUND

Complement-activating naturally occurring anti-porcine endothelial cell antibodies (Abs) are responsible for hyperacute rejection in porcine-to-primate transplantation, whereas the role of complement in acute vascular rejection, characterized by type II endothelial cell activation, is less well understood. We previously demonstrated a correlation between porcine type II endothelial cell activation, as detected by E-selectin expression, and human immunoglobulin (Ig)G3 anti-Gal alpha1-3Gal (Gal) Abs, which was not seen for IgG1, IgG2 or IgG4. The present study was undertaken to investigate whether there is a causal relationship between human anti-porcine IgG3 Abs and porcine endothelial cell activation.

METHODS

IgG3 was isolated employing a Protein A column to 98.3% purity. Porcine endothelial cells were incubated with isolated human IgG3 or the combination of IgG1, IgG2 and IgG4. E-selectin expression and complement activation were investigated by flow cytometry and Western blotting, respectively.

RESULTS

Purified IgG3, in contrast to the other IgG subclasses, induced a substantial increase in E-selectin expression. This activation was accompanied by complement activation as detected by C3 cleavage, and was abolished by heat inactivation or by adding the complement inhibitor FUT-175. Depletion of anti-Gal Abs reduced E-selectin expression by 60%, consistent with the presence of complement-activating anti-porcine non-Gal Abs of the IgG3 subclass.

CONCLUSIONS

Collectively, these data strengthen the hypothesis that human anti-porcine endothelial cell Abs of the IgG3 subclass are essential for endothelial cell activation in porcine-to-human species grafts and demonstrate such activation to be partly independent of Gal epitopes.

Coy decoy with a new ploy: interceptor controls the levels of homeostatic chemokines

A new subfamily of chemokine receptors is emerging that do not signal along classical G-protein-mediated pathways. Instead, these "silent" receptors efficiently internalize their cognate chemokine ligands, hence their suggested name, "chemokine interceptors", for internalizing receptors. Two of these interceptors, DARC and D6, possess intriguing patterns of tissue expression and are believed to be involved in controlling the local levels of proinflammatory chemokines. In this issue of the European Journal of Immunology, the biochemical properties of a third silent chemokine receptor, CCX-CKR, have been characterized and it is suggested that it may act as a scavenger for homeostatic chemokines, pointing to a broad and significant role for this group of chemokine binding molecules in chemokine biology.