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Pathogen-and injury-related danger signals as well as cytokines released by immune cells influence the functional differentiation of macrophages in chronic inflammation. Recently, the liver-derived plasma protein, histidine-rich glycoprotein (HRG), was demonstrated, in mouse tumor models, to mediate the transition of alternatively activated (M2) to proinflammatory (M1) macrophages, which limit tumor growth and metastasis. We hypothesized that liver-derived HRG is a critical endogenous modulator of hepatic macrophage functionality and investigated its implications for liver inflammation and fibrosis by comparing C57BL/ 6N wild-type (WT) and Hrg 2/2 mice. In homeostatic conditions, hepatic macrophages were overall reduced and preferentially polarized toward the anti-inflammatory M2 subtype in Hrg 2/2 mice. Upon chronic liver damage induced by CCl 4 or methionine-choline-deficient (MCD) diet, liver injury and fibrosis were attenuated in Hrg 2/2 , compared to WT, mice. Macrophage populations were reduced and skewed toward M2 polarization in injured livers of Hrg 2/2 mice. Moreover, HRGdeficient mice showed significantly enhanced hepatic vascularization by micro-computed tomography and histology, corroborating proangiogenic activities of M2-polarized liver macrophages. Purified HRG protein induced, but HRG-deficient serum prevented, M1 macrophage differentiation in vitro. Accordingly, Hrg 2/2 mice transplanted with Hrg 1/1 bone marrow, but not Hrg 2/2 -transplanted Hrg 1/1 mice, remained protected from experimental steatohepatitis. Consistent with these findings, patients with chronic hepatitis C and nonalcoholic steatohepatitis significantly up-regulated hepatocytic HRG expression, which was associated with M1 polarization of adjacent macrophages. Conclusions: Liver-derived HRG, similar to alarmins, appears to be an endogenous molecular factor promoting polarization of hepatic macrophages toward the M1 phenotype, thereby promoting chronic liver injury and fibrosis progression, but limiting angiogenesis. Therefore, controlling tissue levels of HRG or PGF might be a promising strategy in chronic inflammatory liver diseases. (HEPATOLOGY 2016;63:1310-1324

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Lymphopenia and functional defects in lymphocytes may impact the prognosis in patients with critical illness or sepsis. Therefore, we prospectively analyzed peripheral blood leukocytes from 63 healthy volunteers, 50 non-critically ill standard care (SC) patients with infections, and 105 intensive care unit (ICU) patients (52 with sepsis, 53 without sepsis) using flow cytometry. Compared to healthy volunteers, SC and ICU patients showed significant leukocytosis, especially in sepsis, while lymphocyte numbers were significantly decreased. All major lymphocyte populations (B, T, and natural killer (NK) cells) decreased in ICU patients. However, we observed a relative reduction of T cells, alongside decreased CD8+ T cells, in critically ill patients, independent of sepsis. High absolute T cell counts (>0.36/nL) at ICU admission were associated with a significantly reduced mortality, independent of patient’s age. Moreover, patients that survived ICU treatment showed dynamic changes within 48 h towards restoration of lymphopenia and T cell depletion, while non-surviving patients failed to restore lymphocyte counts. In conclusion, the flow-cytometric analysis of peripheral blood revealed striking changes in circulating lymphocyte subsets in critically ill patients, independent of sepsis. Lymphopenia and T cell depletion at ICU admission were associated with increased mortality, supporting their relevance as predictive biomarkers and potential therapeutic targets in intensive care medicine.

Background: Circulating levels of soluble urokinase plasminogen activation receptor (suPAR) have been proposed as a prognostic biomarker in patients with critical illness and sepsis. However, the origin of suPAR in sepsis has remained obscure. We investigated the potential cellular sources of suPAR by analyzing membrane-bound urokinase plasminogen activator receptor (uPAR, CD87) and evaluated its clinical relevance in critically ill patients. Methods: We studied 87 critically ill patients (44 with sepsis, 43 without sepsis) from the medical intensive care unit (ICU) in comparison to 48 standard care patients with infections and 27 healthy controls in a prospective single-center noninterventional cohort study. Cellular uPAR expression of different immune cell subsets (by flow cytometry from peripheral blood) and corresponding serum suPAR concentrations were determined upon ICU admission and at day 3. Furthermore, we analyzed the effects of serum from sepsis patients on the activation and uPAR cleavage of primary human neutrophils and macrophages in vitro. Results: In healthy controls, uPAR (CD87) expression was detected on nearly all blood neutrophils and monocytes, but only scarcely on lymphocytes. While uPAR expression on monocytes was maintained in ICU patients, only 58% of neutrophils from critically ill patients expressed uPAR, which was significantly lower than in healthy controls or standard care patients. Concomitantly, serum suPAR levels were significantly increased in ICU patients. We noted a clear inverse correlation between low neutrophilic uPAR and high serum suPAR in standard care and ICU patients, indicating that shedding of uPAR from activated neutrophils represents a main source of suPAR in systemic inflammation. Both low uPAR and high suPAR were closely associated with mortality in critically ill patients. Furthermore, serum from sepsis patients induced uPAR protein expression and subsequent receptor shedding on isolated primary neutrophils, but not on macrophages, in vitro. Conclusions: The inverse correlation between low uPAR surface expression on neutrophils and high serum suPAR in critically ill patients supports that neutrophils are a main source of shed suPAR proteins in systemic inflammation. Furthermore, high suPAR levels and low neutrophilic uPAR expression predict mortality in ICU patients.

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The human immunodeficiency virus (HIV) continues to be a global pandemic and there is an urgent need for innovative treatment. Immune cells represent a major target of virus infection, but are also therapeutic targets. Currently, no antiretroviral therapy targets macrophages, which function as portal of entry and as major long-term deposit of HIV. It has been shown before that human macrophages efficiently internalize gold nanoparticles, a fact which might be used to target them with drug-nanoparticle conjugates. Here, the authors use gold nanocarriers to facilitate delivery of stavudine, a widely used antiretroviral drug, to primary human macrophages. Using an ease-of-use coupling method, a striking potentiation of stavudine intake by macrophages using gold nanocarriers is shown. Further, the carriers induce a specific subtype of proinflammatory activation indicative for antiviral activity of macrophages, which suggests promising novel treatment options for HIV.

Molecular factors driving immune-mediated inflammation in the liver are incompletely understood. The transcription factor, cyclic adenosine monophosphate-responsive element modulator alpha (CREMa) can endorse differentiation of T lymphocytes toward T-helper (Th)17 cells, thereby promoting autoimmunity in systemic lupus erythematosus or lung inflammation. To investigate the role of CREMa in liver disease, we subjected transgenic (Tg) mice overexpressing CREMa under control of the CD2 promoter (crem tg mice), which restrains expression mainly to lymphocytes (T, natural killer [NK], and NKT cells), to acute and chronic liver injury models. Already in steady state, Tg CREMa overexpression broadly reduced hepatic immune cell numbers by decreasing their viability, but did not affect immune cell migration or the fibrogenic response to chronic liver injury. Strikingly, crem tg mice developed more severe immune-mediated hepatitis with a higher mortality rate, compared to wild-type (wt) mice, upon concanavalin A (ConA) administration. Unlike in T cells from spleen, CREMa overexpression did not induce a predominant Th17 response in intrahepatic T cells, given that hepatic crem tg CD4 1 T cells expressed less interleukin (IL)-17 than wt T cells. Reconstitution of Rag1 2/2 mice with Crem 2/2 T cells did not ameliorate ConA hepatitis. Overexpression of CREMa did not influence NK and NKT-cell effector functions either. Interestingly, a subset of monocytic myeloid-derived suppressor cells (MDSCs) also expressed CD2 and CREMa. Crem tg MDSCs isolated from liver expressed reduced inducible nitric oxide synthase and arginase 1 and displayed a reduced T-cell suppressive activity. The adoptive transfer of wt MDSCs was capable of reducing the fulminant immune-mediated liver damage in crem tg mice to wt level. Conclusion: These results suggest compartmental differences of T cell activation pathways between liver and other organs in autoimmunity and define a functional role of CREMa in hepatic monocytic MDSCs for the pathogenesis of immune-mediated liver disease. (HEPATOLOGY 2015;61:990-1002) A utoimmune hepatitis (AIH) has a wide spectrum of clinical presentations, ranging from asymptomatic disease, acute or chronic hepatitis, to fulminant hepatic failure, and is characterized by intrahepatic lymphocyte activation, interface hepatitis, circulating autoantibodies, hypergammaglobulinemia, and a favorable response to immunosuppression. 1In concordance with other autoimmune diseases, AIH is associated with non-organ-specific antibodies (Abs), such as antinuclear Abs, in the context of hepatic