A Treatment-Decision Score for HIV-Infected Children With Suspected Tuberculosis.

BACKGROUND: Diagnosis of tuberculosis should be improved in children infected with HIV to reduce mortality. We developed prediction scores to guide antituberculosis treatment decision in HIV-infected children with suspected tuberculosis. METHODS: HIV-infected children with suspected tuberculosis enrolled in Burkina Faso, Cambodia, Cameroon, and Vietnam (ANRS 12229 PAANTHER 01 Study), underwent clinical assessment, chest radiography, Quantiferon Gold In-Tube (QFT), abdominal ultrasonography, and sample collection for microbiology, including Xpert MTB/RIF (Xpert). We developed 4 tuberculosis diagnostic models using logistic regression: (1) all predictors included, (2) QFT excluded, (3) ultrasonography excluded, and (4) QFT and ultrasonography excluded. We internally validated the models using resampling. We built a score on the basis of the model with the best area under the receiver operating characteristic curve and parsimony. RESULTS: A total of 438 children were enrolled in the study; 251 (57.3%) had tuberculosis, including 55 (12.6%) with culture- or Xpert-confirmed tuberculosis. The final 4 models included Xpert, fever lasting >2 weeks, unremitting cough, hemoptysis and weight loss in the past 4 weeks, contact with a patient with smear-positive tuberculosis, tachycardia, miliary tuberculosis, alveolar opacities, and lymph nodes on the chest radiograph, together with abdominal lymph nodes on the ultrasound and QFT results. The areas under the receiver operating characteristic curves were 0.866, 0.861, 0.850, and 0.846, for models 1, 2, 3, and 4, respectively. The score developed on model 2 had a sensitivity of 88.6% and a specificity of 61.2% for a tuberculosis diagnosis. CONCLUSIONS: Our score had a good diagnostic performance. Used in an algorithm, it should enable prompt treatment decision in children with suspected tuberculosis and a high mortality risk, thus contributing to significant public health benefits.

Ex vivo conditioning with IL-12 protects tumor-infiltrating CD8+ T cells from negative regulation by local IFN-γ.

Optimal ex vivo expansion protocols for adoptive cell therapy (ACT) must yield T cells able to effectively home to tumors and survive the inhospitable conditions of the tumor microenvironment (TME), while simultaneously exerting persistent anti-tumor effector functions. Our previous work has shown that ex vivo activation in the presence of IL-12 can induce optimal expansion of murine CD8+ T cells, thus resulting in significant tumor regression after ACT mostly via sustained secretion of IFN-γ. In this report, we further elucidate the mechanism of this potency, showing that IL-12 additionally counteracts the negative regulatory effects of autocrine IFN-γ. IL-12 not only downregulates PD-1 expression by T cells, thus minimizing the effects of IFN-γ-induced PD-L1 upregulation by tumor stromal cells, but also inhibits IFNγR2 expression, thereby protecting T cells from IFN-γ-induced cell death. Thus, the enhanced anti-tumor activity of CD8+ T cells expanded ex vivo in the presence of IL-12 is due not only to the ability of IL-12-stimulated cells to secrete sustained levels of IFN-γ, but also to the additional capacity of IL-12 to counter the negative regulatory effects of autocrine IFN-γ.

IFN-γR2 is strongly expressed on endothelial cells of gingival tissues from patients with chronic periodontitis.

OBJECTIVE: Chronic periodontitis (CP) is characterized by gingival inflammation and bone destruction. It has been reported that interferon-gamma (IFN-γ) levels are high in CP patients; however, the IFN-γ receptor (IFN-γR) has not been studied in gingival tissue from these patients. To evaluate IFN-γ levels and IFN-γR expression in gingival tissue biopsies from chronic periodontitis patients compared with healthy subjects (HS). MATERIAL AND METHODS: Gingival tissues were obtained from all study subjects, CP (n = 18) and healthy subjects (HS) (n = 12). A tissue section of each study subject was embedded in paraffin blocks to determine the expression of IFN-γ R (IFN-γR1 and IFN-γR2) through immunohistochemistry. Another section of the tissue was homogenized and IFN-γ was measured by the ELISA technique. RESULTS: No significant differences were found in the IFN-γR1 expression within the cell layers of the gingival tissue of the study groups. When analyzing the IFN-γR2 expression it was found that IFN-γR2 is strongly expressed in the endothelial cells of CP patients when compared to HS (p<0.05). IFN-γ concentrations in the gingival tissue were significantly higher in CP patients than in HS. No significant correlation between IFN-γ levels and the expression of IFN-γR1 and IFN-γR2 was found. However, a positive correlation between IFN-γ levels and clinical parameters [probing depth (PD) and clinical attachment level (CAL)] was found. CONCLUSION: The study of IFN-γR expression in gingival tissue samples from patients with CP showed an increase only in the IFN-γR2 chain in endothelial cells when compared to HS.

IFN-γR2 is strongly expressed on endothelial cells of gingival tissues from patients with chronic periodontitis

Abstract Chronic periodontitis (CP) is characterized by gingival inflammation and bone destruction. It has been reported that interferon-gamma (IFN-γ) levels are high in CP patients; however, the IFN-γ receptor (IFN-γR) has not been studied in gingival tissue from these patients. Objective: To evaluate IFN-γ levels and IFN-γR expression in gingival tissue biopsies from chronic periodontitis patients compared with healthy subjects (HS). Material and Methods: Gingival tissues were obtained from all study subjects, CP (n = 18) and healthy subjects (HS) (n = 12). A tissue section of each study subject was embedded in paraffin blocks to determine the expression of IFN-γ R (IFN-γR1 and IFN-γR2) through immunohistochemistry. Another section of the tissue was homogenized and IFN-γ was measured by the ELISA technique. Results: No significant differences were found in the IFN-γR1 expression within the cell layers of the gingival tissue of the study groups. When analyzing the IFN-γR2 expression it was found that IFN-γR2 is strongly expressed in the endothelial cells of CP patients when compared to HS (p<0.05). IFN-γ concentrations in the gingival tissue were significantly higher in CP patients than in HS. No significant correlation between IFN-γ levels and the expression of IFN-γR1 and IFN-γR2 was found. However, a positive correlation between IFN-γ levels and clinical parameters [probing depth (PD) and clinical attachment level (CAL)] was found. Conclusion: The study of IFN-γR expression in gingival tissue samples from patients with CP showed an increase only in the IFN-γR2 chain in endothelial cells when compared to HS.

Improving the spectral analysis of Fluorescence Resonance Energy Transfer in live cells: application to interferon receptors and Janus kinases.

The observed Fluorescence Resonance Energy Transfer (FRET) between fluorescently labeled proteins varies in cells. To understand how this variation affects our interpretation of how proteins interact in cells, we developed a protocol that mathematically separates donor-independent and donor-dependent excitations of acceptor, determines the electromagnetic interaction of donors and acceptors, and quantifies the efficiency of the interaction of donors and acceptors. By analyzing large populations of cells, we found that misbalanced or insufficient expression of acceptor or donor as well as their inefficient or reversible interaction influenced FRET efficiency in vivo. Use of red-shifted donors and acceptors gave spectra with less endogenous fluorescence but produced lower FRET efficiency, possibly caused by reduced quenching of red-shifted fluorophores in cells. Additionally, cryptic interactions between jellyfish FPs artefactually increased the apparent FRET efficiency. Our protocol can distinguish specific and nonspecific protein interactions even within highly constrained environments as plasma membranes. Overall, accurate FRET estimations in cells or within complex environments can be obtained by a combination of proper data analysis, study of sufficient numbers of cells, and use of properly empirically developed fluorescent proteins.

Th17 cells in multiple sclerosis express higher levels of JAK2, which increases their surface expression of IFN-γR2.

IFN-ß inhibits the expansion of Th17 cells in active multiple sclerosis (AMS), and this might contribute to improve the clinical symptoms. The effectiveness of this inhibition, however, requires intact IFN-γ signaling in T cells. In this study, we report that both mRNA and cell surface expression of the signaling chain of the IFN-γ receptor (IFN-γR2) and its cognate tyrosine kinase JAK2 are enhanced in peripheral blood Th17 cells and clones from patients with AMS compared with those with inactive multiple sclerosis (IMS) or healthy subjects (HS). IFN-γ decreased the frequency of Th17 peripheral cells and proliferation of Th17 clones from AMS patients. Stimulation of PBMCs from HS in Th17-polarizing conditions resulted in the enhancement of JAK2 expression and accumulation of cell surface IFN-γR2. The role of JAK2 in the modulation of IFN-γR2 was demonstrated as its transduction prevented rapid internalization and degradation of IFN-γR2 in JAK2-deficient γ2A cells. In conclusion, these data identify JAK2 as a critical factor that stabilizes IFN-γR2 surface expression in Th17 cells from AMS patients, making them sensitive to IFN-γ. These data may have clinical implications for a better use of IFNs in multiple sclerosis and possibly other inflammatory diseases.

The hydroxy-naphthoquinone lapachol arrests mycobacterial growth and immunomodulates host macrophages.

The present study reports the anti-mycobacterial activity of 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone (lapachol) as well as its influence on macrophage functions. Lapachol (L) did not induce apoptosis/necrosis of THP-1 macrophages at ≤32 µg/mL. Mycobacterium avium liquid growth was arrested by ≥32 µg/mL and intra-macrophage proliferation by ≥16 µg/mL lapachol. The main immuno-modulatory effects of lapachol observed were an up-regulation of interferon-γ-receptor 1 (IFN-γR1) and major histocompatibility complex class II (MHCII) surface expression, and a marked inhibition of IL-10 secretion. Lapachol did not affect resting, IFN-γ- or toll-like receptor 2 (TLR2)-induced levels of oxygen and nitrogen metabolism key proteins nor the TLR2-mediated secretion of TNF-α, nor induced either oxidative or endoplasmic reticulum (ER) stress. Lapachol inhibited the surface expression of the co-stimulatory molecule CD86 but not that of CD80 and CD83. The results obtained indicate that the substituted naphthoquinone lapachol exhibits an anti-mycobacterial activity that is more efficient intra- than extra-cellularly, and exerts immuno-modulatory effects some of which may enhance the capacity of the host cell to control mycobacterial growth. The immune-modulatory action of lapachol could contribute to its more efficient intra-macrophage anti-mycobacterial activity.

Urinary evaluation of the balance between the soluble interferon-gamma receptor (IFN-gammaR1) and the interleukin-4 receptor (IL-4Ralpha) in children with vesicoureteral reflux.

We planned to investigate the urinary soluble cytokine receptor profile in patients with vesico-ureteric reflux (VUR). The urine levels of soluble interferon-gamma receptor R1 (sIFN-gammaR) and soluble interleukin-4 receptor alpha (sIL-4R) were measured using an ELISA technique. The urine levels of sIFN-gammaR in the patients with VUR were significantly higher than those in the healthy controls (p < 0.001). On the other hand, although the urine sIL-4R levels in the patients with VUR were also higher than those in the controls, there were no significant differences between them. The urinary soluble receptor levels did not correlate with the clinical severity of VUR. These results suggest that there may be an immunological basis to VUR complicatedly.

Activation of the interferon-gamma signaling pathway in systemic lupus erythematosus peripheral blood mononuclear cells.

OBJECTIVE: To investigate interferon-gamma (IFNgamma) signaling in peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE) by analyzing IFNgamma receptor (IFNgammaR) expression, STAT-1 expression and phosphorylation, and the regulation of IFNgamma-inducible genes. METHODS: Fluorocytometry was used to investigate expression of STAT-1, pSTAT-1, CD95, HLA-DR, class I major histocompatibility complex (MHC), IFNgamma-inducible 10-kd protein (IP-10), monokine induced by IFNgamma (Mig), and IFNgammaR in PBMCs from SLE patients and healthy individuals. STAT-1 phosphorylation was determined by fluorocytometry and Western blotting after stimulation with IFNalpha or IFNgamma. Quantitative polymerase chain reaction was used to assess messenger RNA (mRNA) expression of the IFNgamma-inducible genes IP-10 and Mig shortly after preparation or after stimulation with IFNgamma in monocytes. RESULTS: STAT-1 expression was increased in PBMCs from SLE patients and correlated significantly with disease activity and with the IFN-inducible expression of CD95 and HLA-DR. STAT-1 expression also showed a trend toward association with class I MHC expression. In addition, the expression of other IFNgamma-inducible genes, such as IP-10 or Mig, was increased in SLE monocytes. While STAT-1 phosphorylation in SLE PBMCs and PBMCs from healthy individuals was similar after IFNalpha stimulation, incubation with IFNgamma induced STAT-1 phosphorylation only in SLE lymphocytes. Moreover, SLE monocytes showed a considerably higher increase in pSTAT-1 expression upon IFNgamma stimulation than monocytes from healthy individuals. Increased responsiveness of SLE monocytes to IFNgamma was also confirmed on the mRNA level, where expression of the IFN-inducible, STAT-1-dependent genes IP-10 and Mig was more efficiently increased in SLE cells. However, IFNgammaR was similarly expressed on SLE lymphocytes and monocytes and those from healthy individuals. CONCLUSION: In addition to supporting the role of IFNs in SLE immunopathogenesis in general, the findings of the present study support a role of IFNgamma in this disease.

Urinary evaluation of the balance between soluble interferon-gamma receptor (IFN-gammaR1) and interleukin-4 receptor (IL-4Ralpha).

To elucidate the usefulness of the simultaneous analysis of multiple kinds of soluble cytokine receptors in urine specimens, we determined the levels of both the soluble interferon-gamma receptor alpha chain (sIFN-gammaR1, Th1-type cytokine receptor) and the soluble interleukin 4-receptor alpha chain (sIL-4Ralpha, Th2-type cytokine receptor) in the urine of healthy subjects as reference values and preliminarily applied this method to evaluate patients with diarrhea positive (D+) hemolytic uremic syndrome (HUS) as the diagnostic parameters. The urinary sIFN-gammaR levels of children were significantly lower than those of adults (p < 0.01, n = 107). On the other hand, there was no significant difference between the urine sIL-4R levels of adults and children. Statistical correlation between sIFN-gammaR and sIL-4R values was not observed (p = 0.705). On the day of onset of HUS, the urine sIFN-gammaR levels of the patients (n = 6) with HUS were higher than those of the healthy control group (n = 67) (p < 0.01); however, there was no significant difference in the sIL-4R levels between both groups. The urine evaluation of the balance between the soluble cytokine receptors might be informative for the immune states of HUS patients.

Impact of foetus and mother on IFN-gamma-induced indoleamine 2,3-dioxygenase and inducible nitric oxide synthase expression in murine placenta following Toxoplasma gondii infection.

IFN-gamma production is a hallmark of acute infection with the protozoan parasite Toxoplasma gondii. The tryptophan-catabolising enzyme indoleamine 2,3-dioxygenase (IDO), as well as inducible nitric oxide synthase (NOS2) are induced by IFN-gamma and can play extremely diverse roles in immune regulation, defence against pathogens and physiological homeostasis. We investigated the regulation of these two central enzymes in the placenta during acute infection of pregnant female mice. Using IFN-gamma receptor knockout (IFNgammaR-/-) mice, we showed that IDO is not constitutively expressed in term placentas. In contrast, NOS2 expression was observed, largely dependent on IFN-gamma signalling. Upon infection with the avirulent PRU strain of T. gondii, IDO mRNA expression was induced in an IFNgammaR-dependent manner. Surprisingly, NOS2 mRNA was severely suppressed. Importantly, we showed in crossing experiments of heterozygote (IFNgammaR+/-) mothers with IFNgammaR-/- males and vice versa that IDO expression largely depends on the presence of IFN-gamma receptors on foetal cells, and to a lesser extent on maternal cells. Immunohistochemical analysis localised foetal IDO production to invasive trophoblasts within the maternal part of the placenta. The placental vascular endothelium only stained positive when the mothers possessed functional IFN-gamma receptors. In contrast, placental NOS2 expression, but also its suppression following infection, seems to be largely dependent on IFN-gamma signalling in maternal cells. Neither factor appears to regulate placental T. gondii growth, as we observed no difference in parasite numbers between (+/-) and (-/-) foetuses. Taken together, our results demonstrate the crucial role of the foetus in placental IDO, but not NOS2, production following T. gondii infection.

Gene expression shift towards normal B cells, decreased proliferative capacity and distinct surface receptors characterize leukemic blasts persisting during induction therapy in childhood acute lymphoblastic leukemia.

In childhood acute lymphoblastic leukemia (ALL), persistence of leukemic blasts during therapy is of crucial prognostic significance. In the present study, we address molecular and cell biologic features of blasts persisting after 1 week of induction glucocorticoid therapy. Genome-wide gene expression analysis of leukemic samples from precursor B-cell ALL patients (n=18) identified a set of genes differentially expressed in blasts at diagnosis day 0 (d0) and persisting on day 8 (d8). Expression changes indicate a shift towards mature B cells, inhibition of cell cycling and increased expression of adhesion (CD11b/ITGAM) and cytokine (CD119/IFNGR1) receptors. A direct comparison with normal B cells, which are largely therapy resistant, confirmed the differentiation shift at the mRNA (n=10) and protein (n=109) levels. Flow cytometric analysis in independent cohorts of patients confirmed both a decreased proliferative activity (n=13) and the upregulation of CD11b and CD119 (n=29) in d8 blasts. The differentiation shift and low proliferative activity in d8 blasts may account for the persistence of blasts during therapy and affect their sensitivity to further therapeutic treatment. CD11b and CD119 are potential specific markers for d8 blast persistence and detection of minimal residual disease, which warrant further investigation.

Asymmetric T lymphocyte division in the initiation of adaptive immune responses.

A hallmark of mammalian immunity is the heterogeneity of cell fate that exists among pathogen-experienced lymphocytes. We show that a dividing T lymphocyte initially responding to a microbe exhibits unequal partitioning of proteins that mediate signaling, cell fate specification, and asymmetric cell division. Asymmetric segregation of determinants appears to be coordinated by prolonged interaction between the T cell and its antigen-presenting cell before division. Additionally, the first two daughter T cells displayed phenotypic and functional indicators of being differentially fated toward effector and memory lineages. These results suggest a mechanism by which a single lymphocyte can apportion diverse cell fates necessary for adaptive immunity.

Identification of the zebrafish IFN receptor: implications for the origin of the vertebrate IFN system.

The recent description of virus-induced fish IFNs has raised questions about the evolution of this complex antiviral system. Identification of the receptor of the zebrafish virus-induced IFN (zIFN) was sought to help resolve these questions. We set up an experimental system to study the zIFN system in the course of a viral infection of zebrafish embryos. In this setting, zIFN was induced by viral infection, and we identified zIFN-dependent induced transcripts. Embryos quickly died from the infection, but zIFN overexpression increased their survival. We took advantage of this experimental system to perform in vivo loss and gain of function analysis of candidate receptors of the class II helical receptor family and identified zCRFB1 and zCRFB5 as the two subunits of the zebrafish IFN receptor. Based on the organization of the zIFN gene and the protein structure of the identified receptor components, the virus-induced fish IFNs appear as orthologs of mammalian IFN-lambda, specifying type III IFN as the ancestral antiviral system of vertebrates.

Depressed T cell-derived IFN-gamma following trauma-hemorrhage: a potential mechanism for diminished APC responses.

INTRODUCTION: Prolonged immunosuppression has been demonstrated after trauma-hemorrhage resulting in an increased susceptibility to sepsis. The contribution of antigen-presenting cells (APC) vs T cells to this diminished immune response, however, remains unknown. MATERIALS AND METHODS: To study this, male mice were trauma-hemorrhaged (35 +/- 5 mmHg for 90 min and resuscitation) or sham operated. At 24 h thereafter, spleens were harvested and T cells (via Microbeads) and APC (via adherence) were isolated. Cocultures of combined T cells and APC were established for 48 h, stimulated with ConA and LPS. The T cell-derived cytokine IFN-gamma and IL-12 for APC responses were measured in the supernatants by the multiplex assay. RESULTS: The release of IFN-gamma was suppressed by T cells after trauma-hemorrhage irrespective of whether sham or trauma-hemorrhage APC were added. Trauma-hemorrhaged APC did not affect T cells-derived IFN-gamma release by sham T cells. In contrast, trauma-hemorrhaged T cells depressed the release of IL-12 by APC. The release of IL-12 by trauma-hemorrhaged APC was not altered when sham T cells were cocultured. CONCLUSION: Prolonged immunosuppression after trauma-hemorrhage appears to be predominantly due to diminished T cell function. Thus, attempts to prevent immunodysfunction should be directed towards T cells.

Expression of type I interferon receptor as a predictor of clinical response to interferon-alpha therapy of gastrointestinal cancers.

Interferon (IFN) is used in the treatment of many malignancies and viral disorders. We recently reported a significant correlation between the efficacy of IFN-alpha combined with chemotherapy in the treatment of advanced hepatocellular carcinoma (HCC) and IFN-alpha/type I IFN receptor (IFNAR2) expression. It is possible that the expression of IFNAR2 in gastrointestinal cancerous tissue, apart from HCC, may predict the efficacy of IFN-alpha combination therapy. We investigated the expression of IFNAR2 in 100 gastrointestinal cancerous tissues. IFNAR2 expression was examined using immunohistochemistry, in surgically resected tissue samples (20 esophageal, 20 gastric, 20 colorectal, 20 cholangiocarcinoma, and 20 pancreatic samples). The expression rate of IFNAR2 was 35.0% (7/20), 25.0% (5/20), 20.0% (4/20), 45.0% (9/20), and 25.0% (5/20) in esophageal, gastric cancer, colorectal, cholangiocarcinoma and pancreatic cancer samples, respectively. In our previous report, the expression rate of IFNAR2 in HCC samples was 64.8% (59/91). Thus, the expression rates of IFNAR2 in the five types of gastrointestinal cancers tested here were low, compared with HCC. The clinical efficacy of IFN-alpha mono- or combination therapies in patients with gastrointestinal neoplasms is expected to be lower than in patients with HCC based on the expression level of IFNAR2.

Expression of interferon receptors in pancreatic cancer: identification of a novel prognostic factor.

OBJECTIVES: Interferons (IFNs) are known to have antiproliferative and immunoregulatory activities that are modulated through specific cellular-surface ligands, known as IFN-alpha, -beta, and -gamma receptors. The presence of these receptors and their impact on survival in patients with pancreatic cancer has not been determined. METHODS: Slides were prepared from 46 patients with pancreatic adenocarcinoma. Immunohistochemistry (IHC) was used subsequently to determine the expression of IFN-alpha/beta receptor-chain 2 (IFNalpha/betaR) and IFN-gamma receptor-chain 1 (IFNgammaR). The correlation among IFN-receptor expression, characteristics of neoplasms, and overall patient survival were determined analytically. RESULTS: The IHC performed for pancreatic adenocarcinoma demonstrated a high IFNalpha/betaR expression in 4% (2/46) of patients, moderate expression in 20% (9/46), and faint or no expression in 76% (35/46). IHC confirmed a high expression of IFNgammaR in 52% (24/46) of patients, moderate expression in 35% (16/46), and faint or no expression in the remaining 13% (6/46). A clinicopathologic survey failed to demonstrate any significant correlation between IFNalpha/betaR and IFNgammaR expression with regard to size of neoplasm, vascular or perineural invasion, lymph node metastases, or stage of disease. Kaplan-Meier survival analyses demonstrated a survival advantage in those patients whose neoplasms expressed moderate to high IFNalpha/betaR expression, compared with those with faint or no IFNalpha/betaR expression (22 vs 13 months; P = .012, log-rank test). The expression of IFNgammaR, however, had no impact on patient survival (20 months vs 17 months; P = .66, log-rank test). CONCLUSIONS: The IFNalpha/betaR is an independent prognostic factor in patients with pancreatic cancer.

Expression of Fas ligand by hepatic macrophages in patients with fulminant hepatic failure.

OBJECTIVES: The mechanisms of Fas-Fas ligand (Fas-FasL)-mediated apoptosis in the pathogenesis of fulminant hepatic failure (FHF) have not been well defined. This clinical study was carried out to assess which cells expressed Fas-FasL and to determine their involvement. METHODS: The subjects were 24 patients with FHF who underwent liver transplantation at our institution. For comparison, nine chronic hepatitis (CH) patients and six living liver donors (LD) were also enrolled. Liver tissues were obtained for histological (hematoxylin-eosin, terminal deoxynucleotidyl transferase [TdT]-mediated dUTP-biotin nick-end labeling [TUNEL], immunohistochemistry, and double immunofluorescence staining) and reverse transcription PCR (RT-PCR; cytokines and chemokines) analysis. RESULTS: The numbers of TUNEL-, FasL-, and CD68-positive cells in the livers of patients with FHF were significantly larger than in those with CH or with normal livers. Double immunofluorescence staining showed that FasL was expressed predominantly on liver macrophages and rarely on CD8-positive lymphocytes. RT-PCR study showed increased expression of FasL; interferon-gamma; interleukin-18; macrophage inhibitory protein-1beta; and regulated upon activation, normal T cell expressed and secreted in the livers of patients with FHF compared with those of LD. CONCLUSIONS: Macrophages and their expression of FasL may play roles in the pathogenesis of FHF.

Cutting edge: early IFN-gamma signaling directly enhances primary antiviral CD4+ T cell responses.

IFN-gamma drives CD4+ T cell differentiation toward the Th1 phenotype (Th1) and suppresses Th2 development. Current evidence indicates that IFN-gamma inhibits T cell proliferation and decreases T cell survival. In contrast to the above, we show here that antiviral CD4+ T cell generation after infection is reduced in the absence of IFN-gamma signals. The deficient expansion of cells was not due to perturbations in T cell sensitivity to peptide or to altered migratory patterns through nonlymphoid tissues. Instead, IFN-gamma enhanced early antiviral CD4 responses largely through direct signals into these cells. Our data challenge prevailing dogma and have implications for how the sizes of the CD8+ and CD4+ T cell responses are established.