High CD8+ T Cell Activation Marks a Less Differentiated HIV-1 Specific CD8+ T Cell Response that Is Not Altered by Suppression of Viral Replication

Background

The relationship of elevated T cell activation to altered T cell differentiation profiles, each defining features of HIV-1 infection, has not been extensively explored. We hypothesized that anti-retroviral suppression of T cell activation levels would lead to alterations in the T cell differentiation of total and HIV-1 specific CD8+ T cell responses among recently HIV-1 infected adults.

Methodology/Principal Findings

We performed a longitudinal study simultaneously measuring T cell activation and maturation markers on both total and antigen-specific T cells in recently infected adults: prior to treatment; after the initiation of HAART; and after treatment was halted. Prior to treatment, HIV-1 Gag–specific CD8+ T cells were predominantly of a highly activated, intermediate memory (CD27+CD28−) phenotype, while CMV pp65-specific CD8+ T cells showed a late memory (CD27−CD28−), low activation phenotype. Participants with the highest fraction of late memory (CD27−CD28−) HIV-1-specific CD8+ T cells had higher CD4+ T cell counts (rho = +0.74, p = 0.004). In turn, those with the highest fraction of intermediate memory (CD27+ CD28−) HIV-1 specific CD8+ T cells had high total CD8+ T cell activation (rho = +0.68, p = 0.01), indicating poorer long-term clinical outcomes. The HIV-1 specific T cell differentiation profile was not readily altered by suppression of T cell activation following HAART treatment.

Conclusions/Significance

A more differentiated, less activated HIV-1 specific CD8+ T cell response may be clinically protective. Anti-retroviral treatment initiated two to four months after infection lowered T cell activation but had no effect on the differentiation profile of the HIV-1-specific response. Intervention during the first month of acute infection may be required to shift the differentiation phenotype of HIV-1 specific responses to a more clinically favorable profile.     

Bovine Mammary Gene Expression Profiling during the Onset of Lactation

Background

Lactogenesis includes two stages. Stage I begins a few weeks before parturition. Stage II is initiated around the time of parturition and extends for several days afterwards.

Methodology/Principal Findings

To better understand the molecular events underlying these changes, genome-wide gene expression profiling was conducted using digital gene expression (DGE) on bovine mammary tissue at three time points (on approximately day 35 before parturition (−35 d), day 7 before parturition (−7 d) and day 3 after parturition (+3 d)). Approximately 6.2 million (M), 5.8 million (M) and 6.1 million (M) 21-nt cDNA tags were sequenced in the three cDNA libraries (−35 d, −7 d and +3 d), respectively. After aligning to the reference sequences, the three cDNA libraries included 8,662, 8,363 and 8,359 genes, respectively. With a fold change cutoff criteria of ≥2 or ≤−2 and a false discovery rate (FDR) of ≤0.001, a total of 812 genes were significantly differentially expressed at −7 d compared with −35 d (stage I). Gene ontology analysis showed that those significantly differentially expressed genes were mainly associated with cell cycle, lipid metabolism, immune response and biological adhesion. A total of 1,189 genes were significantly differentially expressed at +3 d compared with −7 d (stage II), and these genes were mainly associated with the immune response and cell cycle. Moreover, there were 1,672 genes significantly differentially expressed at +3 d compared with −35 d. Gene ontology analysis showed that the main differentially expressed genes were those associated with metabolic processes.

Conclusions

The results suggest that the mammary gland begins to lactate not only by a gain of function but also by a broad suppression of function to effectively push most of the cell''s resources towards lactation.     

Jak3 Is Involved in Dendritic Cell Maturation and CCR7-Dependent Migration

Background

CCR7-mediated signalling is important for dendritic cell maturation and homing to the lymph nodes. We have previously demonstrated that Jak3 participates in the signalling pathway of CCR7 in T lymphocytes.

Methodology and Principal Findings

Here, we used Jak3^−/− mice to analyze the role of Jak3 in CCR7-mediated dendritic cells migration and function. First, we found no differences in the generation of DCs from Jak3^−/− bone marrow progenitors, when compared to wild type cells. However, phenotypic analysis of the bone marrow derived DCs obtained from Jak3^−/− mice showed reduced expression of co-stimulatory molecules compared to wild type (Jak3^+/+). In addition, when we analyzed the migration of Jak3^−/− and Jak3^+/+ mature DCs in response to CCL19 and CCL21 chemokines, we found that the absence of Jak3 results in impaired chemotactic responses both in vitro and in vivo. Moreover, lymphocyte proliferation and contact hypersensitivity experiments showed that DC-mediated T lymphocyte activation is reduced in the absence of Jak3.

Conclusion/Significance

Altogether, our data provide strong evidence that Jak3 is important for DC maturation, migration and function, through a CCR7-mediated signalling pathway.     

Heterosexual and Homosexual Partners Practising Unprotected Sex May Develop Allogeneic Immunity and to a Lesser Extent Tolerance

Background

Epidemiological studies suggest that allogeneic immunity may inhibit HIV-1 transmission from mother to baby and is less frequent in multiparous than uniparous women. Alloimmune responses may also be elicited during unprotected heterosexual intercourse, which is associated ex vivo with resistance to HIV infection.

Methodology/Principal Findings

The investigation was carried out in well-defined heterosexual and homosexual monogamous partners, practising unprotected sex and a heterosexual cohort practising protected sex. Allogeneic CD4⁺ and CD8⁺ T cell proliferative responses were elicited by stimulating PBMC with the partners'' irradiated monocytes and compared with 3^rd party unrelated monocytes, using the CFSE method. Significant increase in allogeneic proliferative responses was found in the CD4⁺ and CD8⁺ T cells to the partners'' irradiated monocytes, as compared with 3^rd party unrelated monocytes (p≤0.001). However, a significant decrease in proliferative responses, especially of CD8⁺ T cells to the partners'' compared with 3^rd party monocytes was consistent with tolerization, in both the heterosexual and homosexual partners (p<0.01). Examination of CD4⁺CD25⁺FoxP3⁺ regulatory T cells by flow cytometry revealed a significantly greater proportion of these cells in the homosexual than heterosexual partners practising unprotected sex (p<0.05). Ex vivo studies of infectivity of PBMC with HIV-1 showed significantly greater inhibition of infectivity of PBMC from heterosexual subjects practising unprotected compared with those practising protected sex (p = 0.02).

Conclusions/Significance

Both heterosexual and homosexual monogamous partners practising unprotected sex develop allogeneic CD4⁺ and CD8⁺ T cell proliferative responses to the partners'' unmatched cells and a minority may be tolerized. However, a greater proportion of homosexual rather than heterosexual partners developed CD4⁺CD25FoxP3⁺ regulatory T cells. These results, in addition to finding greater inhibition of HIV-1 infectivity in PBMC ex vivo in heterosexual partners practising unprotected, compared with those practising protected sex, suggest that allogeneic immunity may play a significant role in the immuno-pathogenesis of HIV-1 infection.     

Thymic Alterations in GM2 Gangliosidoses Model Mice

Background

Sandhoff disease is a lysosomal storage disorder characterized by the absence of β-hexosaminidase and storage of GM2 ganglioside and related glycolipids. We have previously found that the progressive neurologic disease induced in Hexb ^−/− mice, an animal model for Sandhoff disease, is associated with the production of pathogenic anti-glycolipid autoantibodies.

Methodology/Principal Findings

In our current study, we report on the alterations in the thymus during the development of mild to severe progressive neurologic disease. The thymus from Hexb ^−/− mice of greater than 15 weeks of age showed a marked decrease in the percentage of immature CD4⁺/CD8⁺ T cells and a significantly increased number of CD4⁺/CD8⁻ T cells. During involution, the levels of both apoptotic thymic cells and IgG deposits to T cells were found to have increased, whilst swollen macrophages were prominently observed, particularly in the cortex. We employed cDNA microarray analysis to monitor gene expression during the involution process and found that genes associated with the immune responses were upregulated, particularly those expressed in macrophages. CXCL13 was one of these upregulated genes and is expressed specifically in the thymus. B1 cells were also found to have increased in the thy mus. It is significant that these alterations in the thymus were reduced in FcRγ additionally disrupted Hexb ^−/− mice.

Conclusions/Significance

These results suggest that the FcRγ chain may render the usually poorly immunogenic thymus into an organ prone to autoimmune responses, including the chemotaxis of B1 cells toward CXCL13.     

NK Cell Terminal Differentiation: Correlated Stepwise Decrease of NKG2A and Acquisition of KIRs

Background

Terminal differentiation of NK cells is crucial in maintaining broad responsiveness to pathogens and discriminating normal cells from cells in distress. Although it is well established that KIRs, in conjunction with NKG2A, play a major role in the NK cell education that determines whether cells will end up competent or hyporesponsive, the events underlying the differentiation are still debated.

Methodology/Principal Findings

A combination of complementary approaches to assess the kinetics of the appearance of each subset during development allowed us to obtain new insights into these terminal stages of differentiation, characterising their gene expression profiles at a pan-genomic level, their distinct surface receptor patterns and their prototypic effector functions. The present study supports the hypothesis that CD56^dim cells derive from the CD56^bright subset and suggests that NK cell responsiveness is determined by persistent inhibitory signals received during their education. We report here the inverse correlation of NKG2A expression with KIR expression and explore whether this correlation bestows functional competence on NK cells. We show that CD56^dimNKG2A⁻KIR⁺ cells display the most differentiated phenotype associated to their unique ability to respond against HLA-E+ target cells. Importantly, after IL-12 + IL-18 stimulation, reacquisition of NKG2A strongly correlates with IFN-γ production in CD56^dimNKG2A⁻ NK cells.

Conclusions/Significance

Together, these findings call for the reclassification of mature human NK cells into distinct subsets and support a new model, in which the NK cell differentiation and functional fate are based on a stepwise decrease of NKG2A and acquisition of KIRs.     

Gene profile of myeloid-derived suppressive cells from the bone marrow of lysosomal acid lipase knock-out mice

Background

Lysosomal acid lipase (LAL) controls development and homeostasis of myeloid lineage cells. Loss of the lysosomal acid lipase (LAL) function leads to expansion of myeloid-derived suppressive cells (MDSCs) that cause myeloproliferative neoplasm.

Methodology/Principal Findings

Affymetrix GeneChip microarray analysis identified detailed intrinsic defects in Ly6G⁺ myeloid lineage cells of LAL knock-out (lal−/−) mice. Ingenuity Pathway Analysis revealed activation of the mammalian target of rapamycin (mTOR) signaling, which functions as a nutrient/energy/redox sensor, and controls cell growth, cell cycle entry, cell survival, and cell motility. Loss of the LAL function led to major alteration of large GTPase and small GTPase signal transduction pathways. lal−/− Ly6G⁺ myeloid cells in the bone marrow showed substantial increase of cell proliferation in association with up-regulation of cyclin and cyclin-dependent kinase (cdk) genes. The epigenetic microenvironment was significantly changed due to the increased expression of multiple histone cluster genes, centromere protein genes and chromosome modification genes. Gene expression of bioenergetic pathways, including glycolysis, aerobic glycolysis, mitochondrial oxidative phosphorylation, and respiratory chain proteins, was also increased, while the mitochondrial function was impaired in lal−/− Ly6G⁺ myeloid cells. The concentration of reactive oxygen species (ROS) was significantly increased accompanied by up-regulation of nitric oxide/ROS production genes in these cells.

Conclusions/Significance

This comprehensive gene profile study for the first time identifies and defines important gene pathways involved in the myeloid lineage cells towards MDSCs using lal−/− mouse model.     

The Ability to Generate Senescent Progeny as a Mechanism Underlying Breast Cancer Cell Heterogeneity

Background

Breast cancer is a remarkably heterogeneous disease. Luminal, basal-like, “normal-like”, and ERBB2+ subgroups were identified and were shown to have different prognoses. The mechanisms underlying this heterogeneity are poorly understood. In our study, we explored the role of cellular differentiation and senescence as a potential cause of heterogeneity.

Methodology/Principal Findings

A panel of breast cancer cell lines, isogenic clones, and breast tumors were used. Based on their ability to generate senescent progeny under low-density clonogenic conditions, we classified breast cancer cell lines as senescent cell progenitor (SCP) and immortal cell progenitor (ICP) subtypes. All SCP cell lines expressed estrogen receptor (ER). Loss of ER expression combined with the accumulation of p21^Cip1 correlated with senescence in these cell lines. p21^Cip1 knockdown, estrogen-mediated ER activation or ectopic ER overexpression protected cells against senescence. In contrast, tamoxifen triggered a robust senescence response. As ER expression has been linked to luminal differentiation, we compared the differentiation status of SCP and ICP cell lines using stem/progenitor, luminal, and myoepithelial markers. The SCP cells produced CD24+ or ER+ luminal-like and ASMA+ myoepithelial-like progeny, in addition to CD44+ stem/progenitor-like cells. In contrast, ICP cell lines acted as differentiation-defective stem/progenitor cells. Some ICP cell lines generated only CD44+/CD24-/ER-/ASMA- progenitor/stem-like cells, and others also produced CD24+/ER- luminal-like, but not ASMA+ myoepithelial-like cells. Furthermore, gene expression profiles clustered SCP cell lines with luminal A and “normal-like” tumors, and ICP cell lines with luminal B and basal-like tumors. The ICP cells displayed higher tumorigenicity in immunodeficient mice.

Conclusions/Significance

Luminal A and “normal-like” breast cancer cell lines were able to generate luminal-like and myoepithelial-like progeny undergoing senescence arrest. In contrast, luminal B/basal-like cell lines acted as stem/progenitor cells with defective differentiation capacities. Our findings suggest that the malignancy of breast tumors is directly correlated with stem/progenitor phenotypes and poor differentiation potential.     

Amelioration of streptozotocin-induced diabetes in mice with cells derived from human marrow stromal cells

Background

Pluri-potent bone marrow stromal cells (MSCs) provide an attractive opportunity to generate unlimited glucose-responsive insulin-producing cells for the treatment of diabetes. We explored the potential for human MSCs (hMSCs) to be differentiated into glucose-responsive cells through a non-viral genetic reprogramming approach.

Methods and Findings

Two hMSC lines were transfected with three genes: PDX-1, NeuroD1 and Ngn3 without subsequent selection, followed by differentiation induction in vitro and transplantation into diabetic mice. Human MSCs expressed mRNAs of the archetypal stem cell markers: Sox2, Oct4, Nanog and CD34, and the endocrine cell markers: PDX-1, NeuroD1, Ngn3, and Nkx6.1. Following gene transfection and differentiation induction, hMSCs expressed insulin in vitro, but were not glucose regulated. After transplantation, hMSCs differentiated further and ∼12.5% of the grafted cells expressed insulin. The graft bearing kidneys contained mRNA of insulin and other key genes required for the functions of beta cells. Mice transplanted with manipulated hMSCs showed reduced blood glucose levels (from 18.9+/−0.75 to 7.63+/−1.63 mM). 13 of the 16 mice became normoglycaemic (6.9+/−0.64 mM), despite the failure to detect the expression of SUR1, a K⁺-ATP channel component required for regulation of insulin secretion.

Conclusions

Our data confirm that hMSCs can be induced to express insulin sufficient to reduce blood glucose in a diabetic mouse model. Our triple gene approach has created cells that seem less glucose responsive in vitro but which become more efficient after transplantation. The maturation process requires further study, particularly the in vivo factors influencing the differentiation, in order to scale up for clinical purposes.     

Genetically Dependent ERBB3 Expression Modulates Antigen Presenting Cell Function and Type 1 Diabetes Risk

Type 1 diabetes (T1D) is an autoimmune disease resulting from the complex interaction between multiple susceptibility genes, environmental factors and the immune system. Over 40 T1D susceptibility regions have been suggested by recent genome-wide association studies; however, the specific genes and their role in the disease remain elusive. The objective of this study is to identify the susceptibility gene(s) in the 12q13 region and investigate the functional link to the disease pathogenesis. A total of 19 SNPs in the 12q13 region were analyzed by the TaqMan assay for 1,434 T1D patients and 1,865 controls. Thirteen of the SNPs are associated with T1D (best p = 4×10⁻¹¹), thus providing confirmatory evidence for at least one susceptibility gene in this region. To identify candidate genes, expression of six genes in the region was analyzed by real-time RT-PCR for PBMCs from 192 T1D patients and 192 controls. SNP genotypes in the 12q13 region are the main factors that determine ERBB3 mRNA levels in PBMCs. The protective genotypes for T1D are associated with higher ERBB3 mRNA level (p<10⁻¹⁰). Furthermore, ERBB3 protein is expressed on the surface of CD11c⁺ cells (dendritic cells and monocytes) in peripheral blood after stimulation with LPS, polyI:C or CpG. Subjects with protective genotypes have significantly higher percentages of ERBB3⁺ monocytes and dendritic cells (p = 1.1×10⁻⁹); and the percentages of ERBB3⁺ cells positively correlate with the ability of APC to stimulate T cell proliferation (R² = 0.90, p<0.0001). Our results indicate that ERBB3 plays a critical role in determining APC function and potentially T1D pathogenesis.     

Abnormal Placental Development and Early Embryonic Lethality in EpCAM-Null Mice

Background

EpCAM (CD326) is encoded by the tacstd1 gene and expressed by a variety of normal and malignant epithelial cells and some leukocytes. Results of previous in vitro experiments suggested that EpCAM is an intercellular adhesion molecule. EpCAM has been extensively studied as a potential tumor marker and immunotherapy target, and more recent studies suggest that EpCAM expression may be characteristic of cancer stem cells.

Methodology/Principal Findings

To gain insights into EpCAM function in vivo, we generated EpCAM −/− mice utilizing an embryonic stem cell line with a tacstd1 allele that had been disrupted. Gene trapping resulted in a protein comprised of the N-terminus of EpCAM encoded by 2 exons of the tacstd1 gene fused in frame to βgeo. EpCAM +/− mice were viable and fertile and exhibited no obvious abnormalities. Examination of EpCAM +/− embryos revealed that βgeo was expressed in several epithelial structures including developing ears (otocysts), eyes, branchial arches, gut, apical ectodermal ridges, lungs, pancreas, hair follicles and others. All EpCAM −/− mice died in utero by E12.5, and were small, developmentally delayed, and displayed prominent placental abnormalities. In developing placentas, EpCAM was expressed throughout the labyrinthine layer and by spongiotrophoblasts as well. Placentas of EpCAM −/− embryos were compact, with thin labyrinthine layers lacking prominent vascularity. Parietal trophoblast giant cells were also dramatically reduced in EpCAM −/− placentas.

Conclusion

EpCAM was required for differentiation or survival of parietal trophoblast giant cells, normal development of the placental labyrinth and establishment of a competent maternal-fetal circulation. The findings in EpCAM-reporter mice suggest involvement of this molecule in development of vital organs including the gut, kidneys, pancreas, lungs, eyes, and limbs.     

The Role of MMP7 and Its Cross-Talk with the FAS/FASL System during the Acquisition of Chemoresistance to Oxaliplatin

Background

The efficacy of oxaliplatin in cancer chemotherapy is limited by the development of drug resistance. MMP7 has been related to the loss of tumor cell response to cytotoxic agents although the exact mechanism is not fully understood. Moreover, MMP7 is an independent prognosis factor for survival in patients with colorectal cancer. The aim of the present study was to analyze the role of MMP7 and its cross-talk with the Fas/FasL system during the acquisition of oxaliplatin resistance in colon cancer cells.

Principal Findings

For this purpose we have developed three different oxaliplatin-resistant cell lines (RHT29, RHCT116 p53^+/+, RHCT116 p53^−/−) from the parental HT29, HCT116 p53^+/+ and HCT116 p53^−/− colon cancer cells. MMP7 basal expression was higher in the resistant compared to the parental cell lines. MMP7 was also upregulated by oxaliplatin in both HT29 (p53 mutant) and RHCT116 p53^−/− but not in the RHCT116 p53^+/+. Inhibition of MMP by 1,10-phenantroline monohydrate or siRNA of MMP7 restores cell sensitivity to oxaliplatin-induced apoptosis in both HT29 and RHCT116 p53^−/− but not in the RHCT116 p53^+/+. Some of these effects are caused by alterations in Fas receptor. Fas is upregulated by oxaliplatin in colon cancer cells, however the RHT29 cells treated with oxaliplatin showed a 3.8-fold lower Fas expression at the cell surface than the HT29 cells. Decrease of Fas at the plasma membrane seems to be caused by MMP7 since its inhibition restores Fas levels. Moreover, functional analysis of Fas demonstrates that this receptor was less potent in inducing apoptosis in RHT29 cells and that its activation induces MAPK signaling in resistant cells.

Conclusions

Taking together, these results suggest that MMP7 is related to the acquisition of oxaliplatin-resistance and that its inhibition restores drug sensitivity by increasing Fas receptor. Furthermore, Fas undergoes a change in its functionality in oxaliplatin-resistant cells inducing survival pathways instead of apoptotic signals.     

Sialoadhesin expressed on IFN-induced monocytes binds HIV-1 and enhances infectivity

Background

HIV-1 infection dysregulates the immune system and alters gene expression in circulating monocytes. Differential gene expression analysis of CD14⁺ monocytes from subjects infected with HIV-1 revealed increased expression of sialoadhesin (Sn, CD169, Siglec 1), a cell adhesion molecule first described in a subset of macrophages activated in chronic inflammatory diseases.

Methodology/Principal Findings

We analyzed sialoadhesin expression on CD14⁺ monocytes by flow cytometry and found significantly higher expression in subjects with elevated viral loads compared to subjects with undetectable viral loads. In cultured CD14⁺ monocytes isolated from healthy individuals, sialoadhesin expression was induced by interferon-α and interferon-γ but not tumor necrosis factor-α. Using a stringent binding assay, sialoadhesin-expressing monocytes adsorbed HIV-1 through interaction with the sialic acid residues on the viral envelope glycoprotein gp120. Furthermore, monocytes expressing sialoadhesin facilitated HIV-1 trans infection of permissive cells, which occurred in the absence of monocyte self-infection.

Conclusions/Significance

Increased sialoadhesin expression on CD14⁺ monocytes occurred in response to HIV-1 infection with maximum expression associated with high viral load. We show that interferons induce sialoadhesin in primary CD14⁺ monocytes, which is consistent with an antiviral response during viremia. Our findings suggest that circulating sialoadhesin-expressing monocytes are capable of binding HIV-1 and effectively delivering virus to target cells thereby enhancing the distribution of HIV-1. Sialoadhesin could disseminate HIV-1 to viral reservoirs during monocyte immunosurveillance or migration to sites of inflammation and then facilitate HIV-1 infection of permissive cells.     

Relationships between Levels of Serum IgE,Cell-Bound IgE,and IgE-Receptors on Peripheral Blood Cells in a Pediatric Population

Background

Elevated serum immunoglobulin (Ig) E is a diagnostic marker of immediate-type allergic reactions. We hypothesize that serum IgE does not necessarily reflect total body IgE because in vivo IgE can be bound to cell surface receptors such as FcεRI and FcεRII (CD23). The aim of this study was to analyze the relationships between levels of serum IgE, cell-bound IgE, and IgE-receptors on peripheral blood cells in a pediatric population.

Methodology

Whole blood samples from 48 children (26 boys, 22 girls, mean age 10,3±5,4 years) were analyzed by flow cytometry for FcεRI, CD23, and cell-bound IgE on dendritic cells (CD11c+MHC class II+), monocytes (CD14+), basophils (CD123+MHC class II-) and neutrophils (myeloperoxidase+). Total serum IgE was measured by ELISA and converted into z-units to account for age-dependent normal ranges. Correlations were calculated using Spearman rank correlation test.

Principal Findings

Dendritic cells, monocytes, basophils, and neutrophils expressed the high affinity IgE-receptor FcεRI. Dendritic cells and monocytes also expressed the low affinity receptor CD23. The majority of IgE-receptor positive cells carried IgE on their surface. Expression of both IgE receptors was tightly correlated with cell-bound IgE. In general, cell-bound IgE on FcεRI+ cells correlated well with serum IgE. However, some patients carried high amounts of cell-bound IgE despite low total serum IgE levels.

Conclusion/Significance

In pediatric patients, levels of age-adjusted serum IgE, cell-bound IgE, and FcεRI correlate. Even in the absence of elevated levels of serum IgE, cell-bound IgE can be detected on peripheral blood cells in a subgroup of patients.     

Functional Contribution of Elevated Circulating and Hepatic Non-Classical CD14+CD16+ Monocytes to Inflammation and Human Liver Fibrosis

Background

Monocyte-derived macrophages critically perpetuate inflammatory responses after liver injury as a prerequisite for organ fibrosis. Experimental murine models identified an essential role for the CCR2-dependent infiltration of classical Gr1/Ly6C⁺ monocytes in hepatic fibrosis. Moreover, the monocyte-related chemokine receptors CCR1 and CCR5 were recently recognized as important fibrosis modulators in mice. In humans, monocytes consist of classical CD14⁺CD16⁻ and non-classical CD14⁺CD16⁺ cells. We aimed at investigating the relevance of monocyte subpopulations for human liver fibrosis, and hypothesized that ‘non-classical’ monocytes critically exert inflammatory as well as profibrogenic functions in patients during liver disease progression.

Methodology/Principal Findings

We analyzed circulating monocyte subsets from freshly drawn blood samples of 226 patients with chronic liver disease (CLD) and 184 healthy controls by FACS analysis. Circulating monocytes were significantly expanded in CLD-patients compared to controls with a marked increase of the non-classical CD14⁺CD16⁺ subset that showed an activated phenotype in patients and correlated with proinflammatory cytokines and clinical progression. Correspondingly, CD14⁺CD16⁺ macrophages massively accumulated in fibrotic/cirrhotic livers, as evidenced by immunofluorescence and FACS. Ligands of monocyte-related chemokine receptors CCR2, CCR1 and CCR5 were expressed at higher levels in fibrotic and cirrhotic livers, while CCL3 and CCL4 were also systemically elevated in CLD-patients. Isolated monocyte/macrophage subpopulations were functionally characterized regarding cytokine/chemokine expression and interactions with primary human hepatic stellate cells (HSC) in vitro. CD14⁺CD16⁺ monocytes released abundant proinflammatory cytokines. Furthermore, CD14⁺CD16⁺, but not CD14⁺CD16⁻ monocytes could directly activate collagen-producing HSC.

Conclusions/Significance

Our data demonstrate the expansion of CD14⁺CD16⁺ monocytes in the circulation and liver of CLD-patients upon disease progression and suggest their functional contribution to the perpetuation of intrahepatic inflammation and profibrogenic HSC activation in liver cirrhosis. The modulation of monocyte-subset recruitment into the liver via chemokines/chemokine receptors and their subsequent differentiation may represent promising approaches for therapeutic interventions in human liver fibrosis.