The liver is the largest solid organ in the body and is critical for metabolic and immune functions. However, little is known about the cells that make up the human liver and its immune microenvironment. Here we report a map of the cellular landscape of the human liver using single-cell RNA sequencing. We provide the transcriptional profiles of 8444 parenchymal and non-parenchymal cells obtained from the fractionation of fresh hepatic tissue from five human livers. Using gene expression patterns, flow cytometry, and immunohistochemical examinations, we identify 20 discrete cell populations of hepatocytes, endothelial cells, cholangiocytes, hepatic stellate cells, B cells, conventional and non-conventional T cells, NK-like cells, and distinct intrahepatic monocyte/macrophage populations. Together, our study presents a comprehensive view of the human liver at single-cell resolution that outlines the characteristics of resident cells in the liver, and in particular provides a map of the human hepatic immune microenvironment.

Mice with targeted deletion of fibrinogen‐like protein 2 (fgl2) spontaneously developed autoimmune glomerulonephritis with increasing age, as did wild‐type recipients reconstituted with fgl2−/− bone marrow. These data implicate FGL2 as an important immunoregulatory molecule and led us to identify the underlying mechanisms. Deficiency of FGL2, produced by CD4+CD25+ regulatory T cells (Treg), resulted in increased T cell proliferation to lectins and alloantigens, T helper 1 (Th1) polarization, and increased numbers of antibody‐producing B cells following immunization with T‐independent antigens. Dendritic cells (DC) were more abundant in fgl2−/− mice and had increased expression of CD80 and MHCII following LPS stimulation. Treg cells were also more abundant in fgl2−/− mice, but their suppressive activity was significantly impaired. Antibody to FGL2 completely inhibited Treg cell activity in vitro. FGL2 inhibited DC maturation and induced apoptosis of B cells through binding to the low affinity FcγRIIB receptor. Collectively, these data suggest that FGL2 contributes to Treg cell activity and inhibits the development of autoimmune disease. This work was supported in part by grants from the Heart and Stroke Foundation of Canada and the Canadian Institutes for Health Research.

A significant challenge to delivering therapeutic doses of nanoparticles to targeted disease sites is the fact that most nanoparticles become trapped in the liver. Liver-resident macrophages, or Kupffer cells, are key cells in the hepatic sequestration of nanoparticles. However, the precise role that the macrophage phenotype plays in nanoparticle uptake is unknown. Here, we show that the human macrophage phenotype modulates hard nanoparticle uptake. Using gold nanoparticles, we examined uptake by human monocyte-derived macrophages that had been driven to a "regulatory" M2 phenotype or an "inflammatory" M1 phenotype and found that M2-type macrophages preferentially take up nanoparticles, with a clear hierarchy among the subtypes (M2c > M2 > M2a > M2b > M1). We also found that stimuli such as LPS/IFN-γ rather than with more "regulatory" stimuli such as TGF-β/IL-10 reduce per cell macrophage nanoparticle uptake by an average of 40%. Primary human Kupffer cells were found to display heterogeneous expression of M1 and M2 markers, and Kupffer cells expressing higher levels of M2 markers (CD163) take up significantly more nanoparticles than Kupffer cells expressing lower levels of surface CD163. Our results demonstrate that hepatic inflammatory microenvironments should be considered when studying liver sequestration of nanoparticles, and that modifying the hepatic microenvironment might offer a tool for enhancing or decreasing this sequestration. Our findings also suggest that models examining the nanoparticle/macrophage interaction should include studies with primary tissue macrophages.

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Fibrinogen-like protein 2 (FGL2) is a multifunctional protein, which has been implicated in the pathogenesis of allograft and xenograft rejection. Previously, FGL2 was shown to inhibit maturation of BM-derived DC and T-cell proliferation. The mechanism of the immunosuppressive activity of FGL2 remains poorly elucidated. Here, we focus on identification of FGL2-specific receptor(s) and their ability to modulate APC activity and allograft survival. Using flow cytometry and surface plasmon resonance analysis, we show that FGL2 binds specifically to Fc gamma receptor (FccR)IIB and FccRIII receptors, which are expressed on the surface of APC, including B lymphocytes, macrophages and DC. Antibody to FccRIIB and FccRIII, or deficiency of these receptors, abrogated FGL2 binding. IntroductionFibrinogen-like protein 2 (FGL2), also known as fibroleukin, was first cloned from cytotoxic T lymphocytes and was classified as a member of the fibrinogen superfamily due to its homology (36%) with fibrinogen b and g chains [1]. Predicted as a type II transmembrane glycoprotein [2], cell membraneassociated FGL2 was shown to exhibit novel prothrombinase activity when associated with cell membranes/phospholipid vesicles [3,4], which has been implicated in the pathogenesis of à These authors contributed equally to this study.Correspondence: Dr. Gary Levy e-mail: glfgl2@attglobal.net DOI 10.1002/eji.200838338 Eur. J. Immunol. 2008. 38: 3114- [7]. The procoagulant activity was shown to depend on the serine 89 at the linear N terminal domain of FGL2 [4].The C terminal globular portion of FGL2 lacks the prothrombinase activity and contains a classical fibrinogen-related domain (FRED), which has been suggested to possess immunomodulatory activity based on several lines of evidence. First, other fibrinogen superfamily members including fibrinogen [8] Results Recombinant FcFGL2 protein binds to APCRecombinant FcFGL2 was generated and purified as described in the Materials and methods. The molecular size of the recombinant proteins was examined by SDS-PAGE, silver staining and Western blotting. FcFGL2 had a molecular weight of approximately 440 kDa under non-reducing conditions, which was confirmed by gel filtration (data not shown), and 110 kDa under reducing conditions (Fig. 1A). These data suggested that FcFGL2 exists as a tetramer, consistent with previous reports [13,21]. The Fc tag had a molecular size of 64 kDa under non-reducing conditions and 33 kDa under reducing conditions, suggesting that Fc is dimeric. Biotinylated FcFGL2 bound to the RAW264.7 cells (mouse macrophage cell lines), BMDC, the B-cell line A20 (which expresses only one Fcg receptor, FcgRIIB), thioglycolate-elicited peritoneal exudates cells (495% macrophages) from C57BL/6J mice, but FcFGL2 did not bind to the B-cell line A20IIA1.6, which does not express FcgRIIB (Fig. 1B) [22]. EL4 cells (a mouse T-cell line) did not bind FcFGL2 (data not shown). As expected, the Fc tag protein alone failed to bind to any of these cells and thus, Fc provided an appropriate negativ...

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We synthesized and analyzed 19 compounds of 3'- (meta-) and 4'- (para-) substituted 2-[(R-phenyl)amine]-1,4-naphthalenediones (PANs) R = p-MeO, p-Me, p-Bu, p-Hex, p-Et, m-Me, m-Et, H, p-Cl, p-Br, m-F, m-Cl, p-COCH(3), m-CN, m-NO(2), m-COOH, and p-COOH. Despite the fact that the nitrogen atom, which binds the quinone with the meta- and para-substituted ring, interferes with the direct conjugation between both rings, the UV-vis spectra of these compounds show the existence of an intramolecular electronic transfer from the respective aniline to the p-naphthoquinone moiety. In accordance with this donor-acceptor character, the cyclic voltammograms of these compounds exhibit two, one-electron reduction waves corresponding to the formation of radical-anion and dianion, where the half-wave potential values vary linearly with the Hammett constants (sigma(x)). The analysis of the different voltammetric parameters (e.g., voltammetric function, anodic/cathodic peak currents ratio, and the separation between the anodic and cathodic potential peaks) show that with the exception of the carboxylic PAN derivatives, all compounds present the same reduction pathway. We investigated the molecular and electronic structures of these compounds using the semiempirical PM3 method and, within the framework of the Density Functional Theory, using the Becke 3LYP hybrid functional with a double zeta split valence basis set. Our theoretical calculations predict that, with the exception of the p-nitro compound, all the compounds are planar molecules where the conjugation degree of the nitrogen lone pair with the quinone system depends on the position and magnitude of the electronic effect of the substituent in the aniline ring. The Laplacians of the critical points (nabla(2)rho), for the C-O bonds, show that the first reduction wave corresponds to the carbonyl group in alpha-position to the aniline, and that the second one-electron transfer is due to the C(4)-O(2) carbonyl reduction. Thus, the higher reaction constant value (rho) obtained for the second one-electron transfer is due to the fact that the displacement of the nonshared electrons of the amino nitrogen merely modifies the electron density of C(4)-O(2) bond. The positive correlation between the LUMO energy values calculated for these compounds and the E(1/2) potentials corresponding to the C(1)-O(1) carbonyl reduction show that the electron addition takes place at the lowest unoccupied molecular orbital, supporting the fact that this wave is also prone to the substituent effect.

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